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Encyclopedia > Puberty

Puberty refers to the process of physical changes by which a child's body becomes an adult body capable of reproduction. Puberty is initiated by hormone signals from the brain to the gonads (the ovaries and testes). In response, the gonads produce a variety of hormones that stimulate the growth, function, or transformation of brain, bones, muscle, skin, breasts, and reproductive organs. Growth accelerates in the first half of puberty and stops at the completion of puberty. Before puberty, body differences between boys and girls are almost entirely restricted to the genitalia. During puberty, major differences of size, shape, composition, and function develop in many body structures and systems. The most obvious of these are referred to as secondary sex characteristics. For other uses, see Child (disambiguation). ... With regard to living things, a body is the integral physical material of an individual. ... This article is about the human developmental stage. ... For other uses, see Reproduction (disambiguation) Reproduction is the biological process by which new individual organisms are produced. ... For other uses, see Hormone (disambiguation). ... The gonad is the organ that makes gametes. ... // For ovary as part of plants see ovary (plants) An ovary is an egg-producing reproductive organ found in female organisms. ... Human male anatomy The testicles, known medically as testes (singular testis), are the male generative glands in animals. ... For other uses, see Brain (disambiguation). ... This article is about the skeletal organs. ... For other uses of Muscle, see Muscle (disambiguation). ... This article is about the organ. ... For other uses, see Breast (disambiguation). ... A sex organ, or primary sexual characteristic, narrowly defined, is any of those parts of the body (which are not always bodily organs according to the strict definition) which are involved in sexual reproduction and constitute the reproductive system in an complex organism; namely: Male: penis (notably the glans penis... This article is about biological human development. ... A sex organ, or primary sexual characteristic, narrowly defined, is any of those parts of the body (which are not always bodily organs according to the strict definition) which are involved in sexual reproduction and constitute the reproductive system in an complex organism; namely: Male: penis (notably the glans penis... A peacock displays his long, colored feathers, an example of his secondary sexual characteristics. ...


In a strict sense, the term puberty (and this article) refers to the bodily changes of sexual maturation rather than the psychosocial and cultural aspects of adolescent development. Adolescence is the period of psychological and social transition between childhood and adulthood. Adolescence largely overlaps the period of puberty, but its boundaries are less precisely defined and it refers as much to the psychosocial and cultural characteristics of development during the teen years as to the physical changes of puberty. This article or section does not cite its references or sources. ... Teen redirects here. ... This article is about the human developmental stage. ...

Contents

Differences between male and female puberty

1 Follicle-stimulating hormone - FSH 2 Luteinizing hormone - LH 3 Progesterone 4 Estrogen 5 Hypothalamus 6 Pituitary gland 7 Ovary 8 Pregnancy - hCG (Human chorionic gonadotropin) 9 Testosterone 10 Testicle 11 Incentives 12 Prolactin - PRL
1 Follicle-stimulating hormone - FSH
2 Luteinizing hormone - LH
3 Progesterone
4 Estrogen
5 Hypothalamus
6 Pituitary gland
7 Ovary
8 Pregnancy - hCG (Human chorionic gonadotropin)
9 Testosterone
10 Testicle
11 Incentives
12 Prolactin - PRL

Two of the most significant differences between puberty in girls and puberty in boys are the age at which it begins, and the major sex steroids involved. Sex steroids, also known as gonadal steroids, are steroid hormones which interact with vertebrate androgen or estrogen receptors. ...


Although there is a wide range of normal ages, on average, girls begin the process of puberty about 1-2 years earlier than boys (with average ages of nine to fourteen for girls and ten to seventeen for boys), and reach completion in a shorter time.[1] Girls attain adult height and reproductive maturity about 4 years after the first physical changes of puberty appear. In contrast, boys accelerate more slowly but continue to grow for about 6 years after the first visible pubertal changes.


The hormone that dominates female development is estradiol, an estrogen. While estradiol promotes growth of breasts and uterus, it is also the principal hormone driving the pubertal growth spurt and epiphyseal maturation and closure.[2] Estradiol levels rise earlier and reach higher levels in women than in men. Estradiol (17β-estradiol) (also oestradiol) is a sex hormone. ... Estriol. ... This article is about female reproductive anatomy. ... The word epiphysis can mean: The pineal gland, one of the endocrine glands. ...


In males, testosterone, an androgen, is the principal sex steroid. While testosterone produces all the male changes characterized as virilization, a substantial product of testosterone metabolism in males is estradiol, though levels rise later and more slowly than in girls. The male growth spurt also begins later, accelerates more slowly, and lasts longer before the epiphyses fuse. Although boys are 2 cm shorter than girls before puberty begins, adult men are on average about 13 cm (5.2 inches) taller than women. Most of this sex difference in adult heights is attributable to a later onset of the growth spurt and a slower progression to completion,[3] a direct result of the later rise and lower adult male levels of estradiol. Testosterone is a steroid hormone from the androgen group. ... Androgen is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of masculine characteristics in vertebrates by binding to androgen receptors. ... In biology and medicine, virilization refers to the development of changes which make a male body different from a female body. ...


Puberty onset

Onset is associated with high GnRH pulsing, which precedes the rise in sex hormones, LH and FSH[4]. Exogenous GnRH pulses cause the onset of puberty.[5] Brain tumors which increase GnRH output may also lead to premature puberty.[6]


The cause of this GnRH rise is contentious. Puberty begins consistently at around 47Kg for girls and 55Kg for boys. This dependence on bodyweight makes leptin a good candidate for causing GnRH rise. It is known that leptin has receptors in the hypothalamus[7] which synthesises GnRH. Furthermore, individuals who are deficient in the leptin pathway fail to initiate puberty[8]. The levels of leptin change in line with the onset of puberty, and then decline to adult levels. RNA expression pattern Orthologs Human Mouse Entrez Ensembl Uniprot Refseq Location Pubmed search Leptin (from the Greek word leptos, meaning thin) is a 16 kDa protein hormone that plays a key role in regulating energy intake and energy expenditure, including the regulation (decrease) of appetite and (increase) of metabolism. ...


Physical changes in males

Testicular size, function, and fertility

In boys, testicular enlargement is the first physical manifestation of puberty (and is termed gonadarche).[9] Testes in prepubertal boys change little in size from about 1 year of age to the onset of puberty, averaging about 2–3 cc in volume and about 1.5-2 cm in length. Testicular size continues to increase throughout puberty, reaching maximal adult size about 6 years later.[10] While 18-20 cc is reportedly an average adult size, there is wide variation in the normal population.[11] Gonadarche refers to the earliest gonadal changes of puberty. ... Human male anatomy The testicles, known medically as testes (singular testis), are the male generative glands in animals. ...


The testes have two primary functions: to produce hormones and to produce sperm. The Leydig cells produce testosterone (as described below), which in turn produces most of the changes of male sexual maturation and maintains libido. However, most of the increasing bulk of testicular tissue is spermatogenic tissue (primarily Sertoli and interstitial cells). The development of sperm production and fertility in males is not as well documented. Sperm can be detected in the morning urine of most boys after the first year of pubertal changes (and occasionally earlier). Potential fertility is reached at about 13 years old in boys, but full fertility will not be gained until 14-16 years of age, although some go through the process faster, reaching it only 1 year later. For other uses, see Hormone (disambiguation). ... A spermatozoon or spermatozoan ( spermatozoa), from the ancient Greek σπέρμα (seed) and (living being) and more commonly known as a sperm cell, is the haploid cell that is the male gamete. ... Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the seminiferous tubules in the testes. ... Testosterone is a steroid hormone from the androgen group. ... For other uses, see Libido (disambiguation). ... A Sertoli cell (a kind of sustentacular cell) is a nurse cell of the testes which is part of a seminiferous tubule. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... Fertility is the natural capability of giving life. ...


Pubic hair

Pubic hair often appears on a boy shortly after the genitalia begin to grow. As in girls, the first appearance of pubic hair is termed pubarche and the pubic hairs are usually first visible at the dorsal (abdominal) base of the penis. The first few hairs are described as stage 2. Stage 3 is usually reached within another 6–12 months, when the hairs are too numerous to count. By stage 4, the pubic hairs densely fill the "pubic triangle." Stage 5 refers to spread of pubic hair to the thighs and upward towards the navel as part of the developing abdominal hair. Pubic hair is hair in the frontal genital area, the crotch, and sometimes at the top of the inside of the legs; these areas form the pubic region. ... The penis (plural penises, penes) is an external male sexual organ. ... Pubic hair is hair in the frontal genital area, the crotch, and sometimes at the top of the inside of the legs; these areas form the pubic region. ... In humans the thigh is the area between the pelvis and buttocks and the knee. ... For other uses, see Navel (disambiguation). ... The term abdominal hair refers to the hair that grows on the abdomen (belly) of humans and non-human mammals, in the region between the pubic area and the thorax (chest). ...


Body and facial hair

Facial hair of a male that has been shaved
Facial hair of a male that has been shaved

In the months and years following the appearance of pubic hair, other areas of skin which respond to androgens develop heavier hair (androgenic hair) in roughly the following sequence: underarm (axillary) hair, perianal hair, upper lip hair, sideburn (preauricular) hair, periareolar hair, and the rest of the beard area. Arm, leg, chest, abdominal, and back hair become heavier more gradually. There is a large range in amount of body hair among adult men, and significant differences in timing and quantity of hair growth among different ethnic groups. Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... One kind of modern beard. ... This article is about the body feature. ... Distribution of androgenic hair on human female and male bodies Androgenic hair, colloquially Body hair, is the terminal hair on the human body developed during and after puberty. ... For the bowling style in cricket, see underarm bowling. ... This page is a candidate to be copied to Wiktionary. ... Edgar Allan Poe grew a moustache later in his life. ... General Ambrose Burnside, who sideburns were presumably named after Sideburns are facial hair in front of the ears. ... For other uses, see Beard (disambiguation). ... The term chest hair is generally used to describe hair that grows on the chest of human males, in the region between the neck and the abdomen. ... The term abdominal hair refers to the hair that grows on the abdomen (belly) of humans and non-human mammals, in the region between the pubic area and the thorax (chest). ...


Voice change

Under the influence of androgens, the voice box, or larynx, grows in both genders. This growth is far more prominent in boys, causing the male voice to drop and deepen, sometimes abruptly but rarely "over night," about one octave, because the longer and thicker vocal folds have a lower fundamental frequency. Voices never "break." A typical 12-year old boy's larynx is larger, even before voice change, than an adult woman's[citation needed]. Occasionally, voice change is accompanied by unsteadiness of vocalization in the early stages of untrained voices. Most of the voice change happens during stage 3-4 of male puberty around the time of peak growth. Full adult pitch is attained at an average age of about 15 years. However, it usually precedes the development of significant facial hair by several months to years. The larynx (IPA læɹɪŋks) is an organ in the neck of mammals involved in protection of the trachea and sound production. ... The larynx (plural larynges), colloquially known as the voicebox, is an organ in the neck of mammals involved in protection of the trachea and sound production. ... For other uses, see Octave (disambiguation). ... The vocal folds, also known commonly as vocal cords, are composed of twin infoldings of mucous membrane stretched horizontally across the larynx. ... Vibration and standing waves in a string, The fundamental and the first 6 overtones The fundamental tone, often referred to simply as the fundamental and abbreviated fo, is the lowest frequency in a harmonic series. ...


Gigantism: Precocious puberty

The name to a particular growth defect that occurs during childhood, from over-exposure to growth hormone. Precocious puberty and a variety of conditions associated with excessive amounts of testosterone or estrogen in childhood will result in tallness by mid-childhood. People affected by Gigantism grow up in height up to 8ft (approximately 2.40 metres) very rarely. However, the acceleration of bone maturation by the early rise of estradiol results in early completion of growth, and adult heights for these children may actually be below average for genetic potential. The possible symptoms is a Normal genetic variation or Hyperthyroidism, XYY syndrome, Overnutrition, Acromegaly, McCune-Albright syndrome etc. Anna Haining Bates with her parents Greek gigas, gigantus (giant) is a condition characterized by excessive height growth and bigness. ... Growth hormone (GH) or somatotropin (STH) is a protein hormone which stimulates growth and cell reproduction in humans and other animals. ... Testosterone is a steroid hormone from the androgen group. ... Estriol. ... Anna Haining Bates with her parents Greek gigas, gigantus (giant) is a condition characterized by excessive height growth and bigness. ... Height is the measurement of distance between a specified point and a corresponding plane of reference. ... This article is about the unit of length. ... This article is about the general scientific term. ... Hyperthyroidism (or overactive thyroid gland) is the clinical syndrome caused by an excess of circulating free thyroxine (T4) or free triiodothyronine (T3), or both. ... Not to be confused with XXY syndrome. ... Overnutrition is a form of malnutrition in which nutrients are oversupplied relative to the amounts required for normal growth, development, and metabolism. ... Acromegaly (from Greek akros high and megas large - extremities enlargement) is a hormonal disorder that results when the pituitary gland produces excess growth hormone (hGH). ... McCune-Albright syndrome (polyostotic fibrous dysplasia), described in 1937 by Donovan James McCune and Fuller Albright, is a genetic disorder of bones, skin pigmentation and hormonal problems along with premature puberty. ...


Male musculature and body shape

By the end of puberty, adult men have heavier bones and nearly twice as much skeletal muscle. Some of the bone growth (e.g., shoulder width and jaw) is disproportionately greater, resulting in noticeably different male and female skeletal shapes. The average adult male has about 150% of the lean body mass of an average female, and about 50% of the body fat. This article is about the skeletal organs. ... For other uses of Muscle, see Muscle (disambiguation). ...


This muscle develops mainly during the later stages of puberty, and muscle growth can continue even after a male is biologically adult. The peak of the so-called "strength spurt," the rate of muscle growth, is attained about one year after a male experiences his peak growth rate.


Body odor, skin changes, acne

Rising levels of androgens can change the fatty acid composition of perspiration, resulting in a more "adult" body odor. As in girls, another androgen effect is increased secretion of oil (sebum) from the skin and the resultant variable amounts of acne. Acne can be prevented or diminished by antibacterial face washes and other compounds and typically fully diminishes at the end of puberty. An antiseptic is a substance that kills or prevents the growth of bacteria on the external surfaces of the body. ... Washing is one way of cleaning, namely with water and often some kind of soap or detergent. ...


Breast development: pubertal gynecomastia

Estradiol is produced from testosterone in male puberty as well as female, and male breasts often respond to the rising estradiol levels. This is termed gynecomastia. In most boys, the breast development is minimal, similar to what would be termed a "breast bud" in a girl, but in some boys, breast growth is substantial. It usually occurs after puberty is underway, may increase for a year or two, and usually diminishes by the end of puberty. It is increased by extra adipose tissue if the boy is overweight. Weight loss for overweight teenagers can help reduce the prominence of gynecomastia but not diminish as to pubertal reasons. Gynecomastia, or gynaecomastia, pronounced is the development of abnormally large mammary glands in males resulting in breast enlargement, which can sometimes cause secretion of milk. ... Estradiol (17β-estradiol) (also oestradiol) is a sex hormone. ... For other uses, see Breast (disambiguation). ... Obesity is a condition in which the natural energy reserve, stored in the fatty tissue of humans and other mammals, is increased to a point where it is associated with certain health conditions or increased mortality. ... Weight loss, in the context of medicine or health or physical fitness, is a reduction of the total body weight, due to a mean loss of fluid, body fat or adipose tissue and/or lean mass, namely bone mineral deposits, muscle, tendon and other connective tissue. ... Obesity is a condition in which the natural energy reserve, stored in the fatty tissue of humans and other mammals, is increased to a point where it is associated with certain health conditions or increased mortality. ...


Although this is a normal part of male puberty for perhaps half of boys, breast development is usually as unwelcome as upper lip hair in girls, and can be removed surgically if it is causing a lot of stress or anxiety in the boy. “Surgeon” redirects here. ... Stress has different meanings in different fields: Look up stress in Wiktionary, the free dictionary. ... Anxiety is a physiological state characterized by cognitive, somatic, emotional, and behavioral components[1]. These components combine to create the feelings that we typically recognize as anger and known as fear, apprehension, or worry. ...


Physical changes in females

Breast development

Developing breasts in stage 4 of 5, with noticeable secondary mounds

The first physical sign of puberty in females is usually a firm, tender lump under the center of the areola(e) of one or both breasts, occurring on average at about 10.5 years of age.[12] This is referred to as thelarche. By the widely used Tanner staging of puberty, this is stage 2 of breast development (stage 1 is a flat, prepubertal breast). Within six to 12 months, the swelling has clearly begun in both sides, softened, and can be felt and seen extending beyond the edges of the areolae. This is stage 3 of breast development. By another 12 months (stage 4), the breasts are approaching mature size and shape, with areolae and papillae forming a secondary mound. In most young women, this mound disappears into the contour of the mature breast (stage 5), although there is so much variation in sizes and shapes of adult breasts that stages 4 and 5 are not always separately identifiable.[13] Image File history File links taken from fr. ... Image File history File links taken from fr. ... okay that is all ... Cross section of the breast of a human female. ... For other uses, see Breast (disambiguation). ... Thelarche is the first stage of secondary (postnatal) breast development, usually occurring at the beginning of puberty in girls. ... The Tanner stages (also known as the Tanner scale) are stages of physical development in children, adolescents and adults. ...


Pubic hair

Pubic hair is often the second unequivocal change of puberty noticed, usually within a few months of thelarche.[14] It is referred to as pubarche and the pubic hairs are usually visible first along the labia. The first few hairs are described as Tanner stage 2.[13] Stage 3 is usually reached within another 6-12 months, when the hairs are too numerous to count and appear on the pubic mound as well. By stage 4, the pubic hairs densely fill the "pubic triangle." Stage 5 refers to spread of pubic hair to the thighs and sometimes as abdominal hair upward towards the navel. In about 15% of girls, the earliest pubic hair appears before breast development begins.[14] Pubic hair is hair in the frontal genital area, the crotch, and sometimes at the top of the inside of the legs; these areas form the pubic region. ... Pubarche refers to the first appearance of pubic hair in a child. ... In human anatomy or in mammals in general, the mons pubis (Latin, pubic mound), also known simply as the mons, is the soft mound of flesh present in women just above the genitals, raised above the surrounding area due to a pad of fat lying just beneath it which protects... In humans the thigh is the area between the pelvis and buttocks and the knee. ... The term abdominal hair refers to the hair that grows on the abdomen (belly) of humans and non-human mammals, in the region between the pubic area and the thorax (chest). ... For other uses, see Navel (disambiguation). ...


Vagina, uterus, ovaries

The mucosal surface of the vagina also changes in response to increasing levels of estrogen, becoming thicker and a duller pink in color (in contrast to the brighter red of the prepubertal vaginal mucosa).[15] Whitish secretions (physiologic leukorrhea) are a normal effect of estrogen as well.[12] In the next 2 years following thelarche, the uterus and ovaries increase in size, and follicles in the ovaries reach larger sizes.[16] The ovaries usually contain small follicular cysts visible by ultrasound.[17][18] The mucous membranes (or mucosae; singular: mucosa) are linings of mostly endodermal origin, covered in epithelium, and are involved in absorption and secretion. ... The vagina, (from Latin, literally sheath or scabbard ) is the tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. ... Estriol. ... Leukorrhea (US) or leukorrhoea (Commonwealth) is a medical term used to describe vaginal discharge during pregnancy. ... This article is about female reproductive anatomy. ... // For ovary as part of plants see ovary (plants) An ovary is an egg-producing reproductive organ found in female organisms. ... Ovarian follicles or Graafian follicles (after Regnier de Graaf) are the roughly spherical cell aggregations in the ovary containing an ovum and from which the egg is released during ovulation. ... This article is about cysts in the body. ... Sonography redirects here. ...


Menstruation and fertility

The first menstrual bleeding is referred to as menarche, and typically occurs about 2 years after thelarche.[14] The average age of menarche in American girls is about 12.75 years.[14] Menses (menstrual periods) are not always regular and monthly in the first 2 years after menarche.[19] Ovulation is necessary for fertility, but may or may not accompany the earliest menses.[20] In postmenarchal girls, about 80% of the cycles were anovulatory in the first year after menarche, 50% in the third and 10% in the sixth year.[19] However, initiation of ovulation after menarche is not inevitable, and a high proportion of girls with continued irregularity several years from menarche will continue to have prolonged irregularity and anovulation, and are at higher risk for reduced fertility.[21] The word nubility is used commonly in the social sciences to designate achievement of fertility. Menstrual cycle In the female reproductive system, the menstrual cycle is a recurring cycle of physiologic changes that occurs in reproductive-age females. ... Menarche (IPA: ) is the first menstrual period, or first menstrual bleeding in the females of human beings. ... Thelarche is the first stage of secondary (postnatal) breast development, usually occurring at the beginning of puberty in girls. ... Ovulation is the process in the menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum (also known as an oocyte, female gamete, or casually, an egg) that participates in reproduction. ... Fertility is the natural capability of giving life. ... Nubility is the state of being marriageable. ...


Body shape, fat distribution, and body composition

During this period, also in response to rising levels of estrogen, the lower half of the pelvis and thus hips widen (providing a larger birth canal).[13][22] Fat tissue increases to a greater percentage of the body composition than in males, especially in the typical female distribution of breasts, hips, buttocks, thighs, upper arms, and pubis. Progressive differences in fat distribution as well as sex differences in local skeletal growth contribute to the typical female body shape by the end of puberty. At age 10 years, the average girl has 6% more body fat than the average boy, but by the end of puberty the average difference is nearly 50%.[23] The pelvis (pl. ... In anatomy, the hip is the bony projection of the femur which is known as the greater trochanter, and the overlying muscle and fat. ... Human female internal reproductive anatomy The vagina (from the Latin for sheath or scabbard ) is the tubular tract leading from the uterus to the exterior of the body in female mammals, or to the cloaca in female birds and some reptiles. ...


Body odor, skin changes, and acne

Rising levels of androgens can change the fatty acid composition of perspiration, resulting in a more "adult" body odor. This often precedes thelarche and pubarche by 1 or more years. Another androgen effect is increased secretion of oil (sebum) from the skin. This change increases the susceptibility to acne, a characteristic affliction of puberty greatly variable in its severity.[24] Androgen is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of masculine characteristics in vertebrates by binding to androgen receptors. ... Not to be confused with fats. ... Perspiration (also called sweating or sometimes transpiration) is the production and evaporation of a fluid, consisting primarily of water as well as a smaller amount of sodium chloride (the main constituent of table salt), that is excreted by the sweat glands in the skin of mammals. ... Bromhidrosis or body odor (also called bromidrosis, osmidrosis and ozochrotia) is the smell of bacteria growing on the body. ... The sebaceous glands are glands found in the skin of mammals. ...


Variations

Typical puberty is described above, but many children vary with respect to timing of onset, tempo, steadiness of continuation, and sequence of events.


Timing of onset

Puberty is a process with a gradual onset beginning with changes of neuronal function in the hypothalamus, resulting in rising hormonal signals between brain and gonads, proceeding to gonadal growth and production of sex steroids, which in turn induce changes in responsive parts of the body. The definition of onset, therefore, depends on the perspective (e.g., hormonal versus physical) and purpose (establishing population normal standards, clinical care of early or late children, or a variety of other social purposes). The most commonly used definition of onset for both social and medical purposes is the appearance of the first physical changes described in this section of this article, but it should be understood that these physical changes are the first outward signs of preceding neural, hormonal, and gonadal function changes that are usually impossible or impractical to detect. The hypothalamus links the nervous system to the endocrine system via the pituitary gland (hypophysis). ... For other uses, see Hormone (disambiguation). ... For other uses, see Brain (disambiguation). ... The gonad is the organ that makes gametes. ... Sex steroids, also known as gonadal steroids, are steroid hormones which interact with vertebrate androgen or estrogen receptors. ...


The age at which puberty begins can vary widely between individuals and between populations. Age of puberty is affected by both genetic factors and by environmental factors such as nutritional state or social circumstances. Timing may also be affected by environmental factors (exogenous hormones and environmental substances with hormone-like effects) and there is even evidence that life experiences may play a role as well.


Ethnic/racial differences have been recognized for centuries. For example, the average age of menarche in various populations surveyed in the last several decades has ranged from 12.0 to 18.5 years. The earliest mean is reported for African-American girls and the oldest for high altitude subsistence populations in Asia. However, it is clear that much of the higher age averages reflect nutritional limitations more than genetic differences and can change within a few generations with a substantial change in diet. The median age of menarche for a population may be an index of the proportion of undernourished girls in the population, and the width of the spread may reflect unevenness of wealth and food distribution in a population. Menarche (IPA: ) is the first menstrual period, or first menstrual bleeding in the females of human beings. ...


Genetic influence

Various studies have found direct genetic effects to account for at least 46% of the variation of timing of puberty in well-nourished populations.[25][26][27][28] The genetic association of timing is strongest between mothers and daughters. The specific genes affecting timing are not defined yet.[25] Among the candidates is an androgen receptor gene.[29] For other uses, see Gene (disambiguation). ... The androgen receptor is an intracellular steroid receptor that specifically binds testosterone and dihydrotestosterone. ...


Environmental factors

If genetic factors account for half of the variation of pubertal timing, environment factors are clearly important as well. One of the earliest observed environmental effects is that puberty occurs later in children raised at higher altitudes. The most important of the environmental influences is clearly nutrition, but a number of others have been identified, all which affect timing of female puberty and menarche more clearly than male puberty.


Nutritional influence

Nutritional factors are the strongest and most obvious environmental factors affecting timing of puberty.[25] Girls are especially sensitive to nutritional regulation because they must contribute all of the nutritional support to a growing fetus. Surplus calories (beyond growth and activity requirements) are reflected in the amount of body fat, which signals to the brain the availability of resources for initiation of puberty and fertility. The Nutrition Facts table indicates the amounts of nutrients which experts recommend you limit or consume in adequate amounts. ... The calorie is a unit of energy, in particular heat. ... Adipose tissue is an anatomical term for loose connective tissue composed of energy in the form of fat, although it also cushions and insulates the body. ...


Much evidence suggests that for most of the last few centuries, nutritional differences accounted for majority of variation of pubertal timing in different populations, and even among social classes in the same population. Recent worldwide increased consumption of animal protein, other changes in nutrition, and increases in childhood obesity have resulted in falling ages of puberty, mainly in those populations with the higher previous ages. In many populations the amount of variation attributable to nutrition is shrinking.


Although available dietary energy (simple calories) is the most important dietary influence on timing of puberty, quality of the diet plays a role as well. Lower protein intakes and higher plant fiber intakes, as occur with typical vegetarian diets, are associated with later onset and slower progression of female puberty. A representation of the 3D structure of myoglobin showing coloured alpha helices. ... Fiber crops are field crops grown for their fibers, which are used to make paper or cloth. ... Vegetarian cuisine is cookery of food that meets vegetarian principles. ...


Studies have shown that calcium deficiency is a cause of late puberty, irregular and painful, cramping during menstruation with excessive blood loss, and lowered immune response to infections in young girls. This could be from a deficient diet or lack of vitamin D from too little sun exposure. This lack of calcium could predispose them to osteoporosis later in life.


Obesity influence

Scientific researchers have linked early obesity with a drop of puberty onset in girls. They have cited obesity as a cause of breast development before nine years and menarche before twelve years. [30] Early puberty in girls can be a harbinger of later health problems. [31]


Physical activity and exercise

The average level of daily physical activity has also been shown to affect timing of puberty, especially female. A high level of exercise, whether for athletic or body image purposes, or for daily subsistence, reduces energy calories available for reproduction and slows puberty. The exercise effect is often amplified by a lower body fat mass.


Physical illness

Many chronic diseases can delay puberty in both boys and girls. Those that involve chronic inflammation or interfere with nutrition have the strongest effect. In the western world, inflammatory bowel disease and tuberculosis have been notorious for such an effect in the last century, while in areas of the underdeveloped world, chronic parasite infections are widespread. In medicine, inflammatory bowel disease (IBD) is a group of inflammatory conditions of the large intestine and, in some cases, the small intestine. ... Tuberculosis (abbreviated as TB for tubercle bacillus or Tuberculosis) is a common and deadly infectious disease caused by mycobacteria, mainly Mycobacterium tuberculosis. ... A parasite is an organism that spends a significant portion of its life in or on the living tissue of a host organism and which causes harm to the host without immediately killing it. ... An infection is the detrimental colonization of a host organism by a foreign species. ...


Environmental chemicals and hormones

There is theoretical concern, and animal evidence, that environmental hormones and chemicals may affect aspects of prenatal or postnatal sexual development in humans. Large amounts of incompletely metabolized estrogens and progestagens from pharmaceutical products are excreted into the sewage systems of large cities, and are sometimes detectable in the environment. Sex steroids are sometimes used in cattle farming but have been banned in chicken meat production for 40 years. Although agricultural laws regulate use to minimize accidental human consumption, the rules are largely self-enforced in the United States. Significant exposure of a child to hormones or other substances that activate estrogen or androgen receptors could produce some or all of the changes of puberty. A chemical substance is any material substance used in or obtained by a process in chemistry: A chemical compound is a substance consisting of two or more chemical elements that are chemically combined in fixed proportions. ... Progestagens (also spelled progestogens or gestagens) are hormones which produce effects similar to progesterone, the only natural progestagen. ... Sex steroids, also known as gonadal steroids, are steroid hormones which interact with vertebrate androgen or estrogen receptors. ... In biochemistry, a receptor is a protein on the cell membrane or within the cytoplasm or cell nucleus that binds to a specific molecule (a ligand), such as a neurotransmitter, hormone, or other substance, and initiates the cellular response to the ligand. ...


Harder to detect as an influence on puberty are the more diffusely distributed environmental chemicals like PCBs (polychlorinated biphenyl), which can bind and trigger estrogen receptors. Labelling transformers containing PCBs. ...


More obvious degrees of partial puberty from direct exposure of young children to small but significant amounts of pharmaceutical sex steroids from exposure at home may be detected during medical evaluation for precocious puberty, but mild effects and the other potential exposures outlined above would not. Precocious puberty means early puberty. ...


Stress and social factors

Some of the least understood environmental influences on timing of puberty are social and psychological. In comparison with the effects of genetics, nutrition, and general health, social influences are small, shifting timing by a few months rather than years. Mechanisms of these social effects are unknown, though a variety of physiological processes, including pheromones, have been suggested based on animal research. Fanning honeybee exposes Nasonov gland (white-at tip of abdomen) releasing pheromone to entice swarm into an empty hive A pheromone (from Greek φέρω phero to bear + ‘ορμόνη hormone) is a chemical that triggers a natural behavioral response in another member of the same species. ...


The most important part of a child's psychosocial environment is the family, and most of the social influence research has investigated features of family structure and function in relation to earlier or later female puberty. Most of the studies have reported that menarche may occur a few months earlier in girls in high-stress households, whose fathers are absent during their early childhood, who have a stepfather in the home, who are subjected to prolonged sexual abuse in childhood, or who are adopted from a developing country at a young age. Conversely, menarche may be slightly later when a girl grows up in a large family with a biological father present. Bad Touch redirects here. ... International adoption refers to adopting a child from a foreign country. ...


More extreme degrees of environmental stress, such as wartime refugee status with threat to physical survival, have been found to be associated with delay of maturation, an effect that may be compounded by dietary inadequacy.


Most of these reported social effects are small and our understanding is incomplete. Most of these "effects" are statistical associations revealed by epidemiologic surveys. Statistical associations are not necessarily causal, and a variety of covariables and alternative explanations can be imagined. Effects of such small size can never be confirmed or refuted for any individual child. Furthermore, interpretations of the data are politically controversial because of the ease with which this type of research can be used for political advocacy. Accusations of bias based on political agenda sometimes accompany scientific criticism. Epidemiology is the study of factors affecting the health and illness of populations, and serves as the foundation and logic of interventions made in the interest of public health and preventive medicine. ...


Another limitation of the social research is that nearly all of it has concerned girls, partly because female puberty requires greater physiologic resources and partly because it involves a unique event (menarche) that makes survey research into female puberty much simpler than male. More detail is provided in the menarche article. Menarche (IPA: ) is the first menstrual period, or first menstrual bleeding in the females of human beings. ...


Variations of tempo and progression

Tempo is the speed at which the process of pubertal changes progresses from beginning to end. The duration of puberty generally varies less than timing of onset, and approximates 4 years for girls and 6 for boys (from first physical changes to attainment of adult height). Nevertheless, some healthy children can proceed through puberty at a faster or slower tempo than most.


An interruption of progression of puberty is usually, but not always, due to abnormal causes such as malnutrition or anorexia nervosa. Perhaps the most common apparently healthy variation is apparent interruption for a couple of years just after attainment of an early sign of initiation. For instance, some girls may seem to develop stage 2 breast buds at 6 or 7 years of age with no other signs of puberty, and nothing may happen for 2 or 3 years. Physicians refer to this as "unsustained puberty." Percentage of population affected by malnutrition by country, according to United Nations statistics. ... For other uses, see Anorexia. ...


Variations of sequence

The sequence of events of pubertal development can occasionally vary. For example, in about 15% of boys and girls, pubarche (the first pubic hairs) can precede, respectively, gonadarche and thelarche by a few months. Rarely, menarche can occur before other signs of puberty in a few girls. These variations deserve medical evaluation because they can occasionally signal a disease. Pubarche refers to the first appearance of pubic hair in a child. ... Gonadarche refers to the earliest gonadal changes of puberty. ... Thelarche is the first stage of secondary (postnatal) breast development, usually occurring at the beginning of puberty in girls. ... Menarche (IPA: ) is the first menstrual period, or first menstrual bleeding in the females of human beings. ...


Conclusion

In a general sense, the conclusion of puberty is reproductive maturity. Criteria for defining the conclusion may differ for different purposes: attainment of the ability to reproduce, achievement of maximal adult height, maximal gonadal size, or adult sex hormone levels. Maximal adult height is achieved at an average age of ~ 15 years for American girls and ~ 18 years for American boys. Potential fertility (sometimes termed nubility) usually precedes completion of growth by 1-2 years in girls and 3-4 years in boys. Stage 5 in the tables above[clarify] typically represents maximal gonadal growth and attainment of adult hormone levels.


Neurohormonal process

The endocrine reproductive system consists of the hypothalamus, the pituitary, the gonads, and the adrenal glands, with input and regulation from many other body systems. True puberty is often termed "central puberty" because it begins as a process of the central nervous system. A simple description of hormonal puberty is as follows: Reproduction is the creation of one thing as a copy of, product of, or replacement for a similar thing, e. ... The hypothalamus links the nervous system to the endocrine system via the pituitary gland (hypophysis). ... | Latin = hypophysis, glandula pituitaria | GraySubject = 275 | GrayPage = 1275 | Image = Gray1180. ... The gonad is the organ that makes gametes. ... In mammals, the adrenal glands (also known as suprarenal glands) are the triangle-shaped endocrine glands that sit on top of the kidneys; their name indicates that position (ad-, near or at + -renes, kidneys). They are chiefly responsible for regulating the stress response through the synthesis of corticosteroids and catecholamines... A diagram showing the CNS: 1. ...

  1. The brain's hypothalamus begins to release pulses of GnRH.
  2. Cells in the anterior pituitary respond by secreting LH and FSH into the circulation.
  3. The ovaries or testes respond to the rising amounts of LH and FSH by growing and beginning to produce estradiol and testosterone.
  4. Rising levels of estradiol and testosterone produce the body changes of female and male puberty.

The onset of this neurohormonal process may precede the first visible body changes by 1-2 years. The hypothalamus links the nervous system to the endocrine system via the pituitary gland (hypophysis). ... Gonadotropin Releasing Hormone (GnRH) is a peptide hormone responsible for the release of FSH and LH from the anterior pituitary. ... Located at the base of the skull, the pituitary gland is protected by a bony structure called the sella turcica. ... Luteinizing hormone (LH) is a hormone synthesized and secreted by gonadotropes in the anterior lobe of the pituitary gland. ... Follicle stimulating hormone (FSH) is a hormone produced by gonadotropes in the anterior pituitary gland. ... // For ovary as part of plants see ovary (plants) An ovary is an egg-producing reproductive organ found in female organisms. ... Human male anatomy The testicles, known medically as testes (singular testis), are the male generative glands in animals. ... Estradiol (17β-estradiol) (also oestradiol) is a sex hormone. ... Testosterone is a steroid hormone from the androgen group. ...


Components of the endocrine reproductive system

The arcuate nucleus of the hypothalamus is the driver of the reproductive system. It has neurons which generate and release pulses of GnRH into the portal venous system of the pituitary gland. The arcuate nucleus is affected and controlled by neuronal input from other areas of the brain and hormonal input from the gonads, adipose tissue and a variety of other systems. The arcuate nucleus is an aggregation of neurons in the mediobasal hypothalamus, adjacent to the third ventricle and the median eminence. ... The hypothalamus links the nervous system to the endocrine system via the pituitary gland (hypophysis). ... This article is about cells in the nervous system. ... | Latin = hypophysis, glandula pituitaria | GraySubject = 275 | GrayPage = 1275 | Image = Gray1180. ... The gonad is the organ that makes gametes. ... Adipose tissue is an anatomical term for loose connective tissue composed of energy in the form of fat, although it also cushions and insulates the body. ...


The pituitary gland responds to the pulsed GnRH signals by releasing LH and FSH into the blood of the general circulation, also in a pulsatile pattern. | Latin = hypophysis, glandula pituitaria | GraySubject = 275 | GrayPage = 1275 | Image = Gray1180. ...


The gonads (testes and ovaries) respond to rising levels of LH and FSH by producing the steroid sex hormones, testosterone and estradiol. Human male anatomy The testicles, known medically as testes (singular testis), are the male generative glands in animals. ... // For ovary as part of plants see ovary (plants) An ovary is an egg-producing reproductive organ found in female organisms. ... This article is about the chemical family of steroids. ... Sex steroids, also known as gonadal steroids, are steroid hormones which interact with vertebrate androgen or estrogen receptors. ... Testosterone is a steroid hormone from the androgen group. ... Estradiol (17β-estradiol) (also oestradiol) is a sex hormone. ...


The adrenal glands are a second source for steroid hormones. Adrenal maturation, termed adrenarche, typically precedes gonadarche in mid-childhood. In mammals, the adrenal glands (also known as suprarenal glands) are the triangle-shaped endocrine glands that sit on top of the kidneys; their name indicates that position (ad-, near or at + -renes, kidneys). They are chiefly responsible for regulating the stress response through the synthesis of corticosteroids and catecholamines... Adrenarche refers to a stage of maturation of the cortex of the human adrenal glands. ...


Major hormones

  • GnRH (gonadotropin-releasing hormone) is a peptide hormone released from the hypothalamus which stimulates gonadotrope cells of the anterior pituitary.
  • LH (luteinizing hormone) is a larger protein hormone secreted into the general circulation by gonadotrope cells of the anterior pituitary gland. The main target cells of LH are the Leydig cells of testes and the theca cells of the ovaries. LH secretion changes more dramatically with the initiation of puberty than FSH, as LH levels increase about 25-fold with the onset of puberty, compared with the 2.5-fold increase of FSH.
  • FSH (follicle stimulating hormone) is another protein hormone secreted into the general circulation by the gonadotrope cells of the anterior pituitary. The main target cells of FSH are the ovarian follicles and the Sertoli cells and spermatogenic tissue of the testes.
  • Testosterone is a steroid hormone produced primarily by the Leydig cells of the testes, and in lesser amounts by the theca cells of the ovaries and the adrenal cortex. Testosterone is the primary mammalian androgen and the "original" anabolic steroid. It acts on androgen receptors in responsive tissue throughout the body.
  • Estradiol is a steroid hormone produced by aromatization of testosterone. Estradiol is the principal human estrogen and acts on estrogen receptors throughout the body. The largest amounts of estradiol are produced by the granulosa cells of the ovaries, but lesser amounts are derived from testicular and adrenal testosterone.
  • Adrenal androgens are steroids produced by the zona reticulosa of the adrenal cortex in both sexes. The major adrenal androgens are dehydroepiandrosterone, androstenedione (which are precursors of testosterone), and dehydroepiandrosterone sulfate which is present in large amounts in the blood. Adrenal androgens contribute to the androgenic events of early puberty in girls.
  • IGF1 (insulin-like growth factor 1) rises substantially during puberty in response to rising levels of growth hormone and may be the principal mediator of the pubertal growth spurt.
  • Leptin is a protein hormone produced by adipose tissue. Its primary target organ is the hypothalamus. The leptin level seems to provide the brain a rough indicator of adipose mass for purposes of regulation of appetite and energy metabolism. It also plays a permissive role in female puberty, which usually will not proceed until an adequate body mass has been achieved.

Gonadotropin-releasing hormone 1 (GNRH1 also called LHRH) is a peptide hormone responsible for the release of FSH and LH from the anterior pituitary. ... Peptides (from the Greek πεπτος, digestible), are the family of short molecules formed from the linking, in a defined order, of various α-amino acids. ... For other uses, see Hormone (disambiguation). ... The hypothalamus links the nervous system to the endocrine system via the pituitary gland (hypophysis). ... Gonadotropes are cells in the anterior pituitary which produce the gonadotropins luteinizing hormone or follicle-stimulating hormone. ... | Latin = hypophysis, glandula pituitaria | GraySubject = 275 | GrayPage = 1275 | Image = Gray1180. ... Luteinizing hormone (LH) is a hormone synthesized and secreted by gonadotropes in the anterior lobe of the pituitary gland. ... Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the seminiferous tubules in the testes. ... The theca folliculi comprise a layer of the ovarian follicles. ... Follicle stimulating hormone (FSH) is a hormone produced by gonadotropes in the anterior pituitary gland. ... Ovarian follicles or Graafian follicles (after Regnier de Graaf) are the roughly spherical cell aggregations in the ovary containing an ovum and from which the egg is released during ovulation. ... A Sertoli cell (a kind of sustentacular cell) is a nurse cell of the testes which is part of a seminiferous tubule. ... Cross section of the epithelium of a seminiferous tubule showing various stages of spermatocyte development Spermatogenesis is the process by which male spermatogonia develop into mature spermatozoa. ... Testosterone is a steroid hormone from the androgen group. ... The theca folliculi comprise a layer of the ovarian follicles. ... Androgen is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of masculine characteristics in vertebrates by binding to androgen receptors. ... Crystal structure of human sex hormone-binding globulin, transporting 5α-dihydrotestosterone. ... The androgen receptor is an intracellular steroid receptor that specifically binds testosterone and dihydrotestosterone. ... Estradiol (17β-estradiol) (also oestradiol) is a sex hormone. ... This article is about the chemical family of steroids. ... In chemistry, an aromatic molecule is one in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone. ... Estriol. ... The estrogen receptor is a receptor for estradiol (the main endogenous estrogen); it is located intracellularly, in parallel with other steroid hormone receptors. ... A granulosa cell is a supporting cell for the developing female gamete in the ovary of mammals. ... Androgen is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of masculine characteristics in vertebrates by binding to androgen receptors. ... Cortical part of the adrenal gland (on the pointer). ... Dehydroepiandrosterone (DHEA), is a natural steroid prohormone produced from cholesterol by the adrenal glands, the gonads, adipose tissue, brain and in the skin (by an autocrine mechanism)]. DHEA is the precursor of androstenedione, testosterone and estrogen. ... Androstenedione (also known as 4-androstenedione) is a 19-carbon steroid hormone produced in the adrenal glands and the gonads as an intermediate step in the biochemical pathway that produces the androgen testosterone and the estrogens estrone and estradiol. ... Dehydroepiandrosterone (DHEA) is a natural steroid hormone produced from cholesterol by the adrenal glands found atop of the kidneys in the human body. ... Insulin-like growth factor 1 (IGF-1) is a polypeptide protein hormone similar in molecular structure to insulin. ... Growth hormone (GH) or somatotropin (STH) is a protein hormone which stimulates growth and cell reproduction in humans and other animals. ... RNA expression pattern Orthologs Human Mouse Entrez Ensembl Uniprot Refseq Location Pubmed search Leptin (from the Greek word leptos, meaning thin) is a 16 kDa protein hormone that plays a key role in regulating energy intake and energy expenditure, including the regulation (decrease) of appetite and (increase) of metabolism. ... Adipose tissue is one of the main types of connective tissue. ... The appetite is the desire to eat food, felt as hunger. ... Bioenergetic may refer to: In biology: Biological thermodynamics, the study of energy transformation In psychology: Bioenergetic analysis, a type of body-oriented psychotherapy based on energy flows MeSH Bioenergetics Dictionary at eMedicine Bioenergetics Dorlands/Elsevier b_11/12185113 Category: ...

Endocrine perspective

The endocrine reproductive system becomes functional by the end of the first trimester of fetal life. The testes and ovaries become briefly inactive around the time of birth but resume hormonal activity until several months after birth, when incompletely understood mechanisms in the brain begin to suppress the activity of the arcuate nucleus. This has been referred to as maturation of the prepubertal "gonadostat," which becomes sensitive to negative feedback by sex steroids. The endocrine system is an integrated system of small organs that involve the release of extracellular signaling molecules known as hormones. ... The human gestation period of approximately 40 weeks between the time of the last menstrual cycle and delivery is traditionally divided into three periods of three months, or trimesters. ... Sex steroids, also known as gonadal steroids, are steroid hormones which interact with vertebrate androgen or estrogen receptors. ...


Gonadotropin and sex steroid levels fall to low levels (nearly undetectable by current clinical assays) for approximately another 8 to 10 years of childhood. Evidence is accumulating that the reproductive system is not totally inactive during the childhood years. Subtle increases in gonadotropin pulses occur, and ovarian follicles surrounding germ cells (future eggs) double in number. Gonadotropins are protein hormones secreted by gonadotrope cells of the pituitary gland of vertebrates. ... A medical test is any kind of diagnostic medical procedure performed for health reasons. ... A germ cell is part of the germline and is involved in the reproduction of organisms. ... A human ovum Sperm cells attempting to fertilize an ovum An ovum (plural ova) is a haploid female reproductive cell or gamete. ...


Normal puberty is initiated in the hypothalamus, with de-inhibition of the pulse generator in the arcuate nucleus. This inhibition of the arcuate nucleus is an ongoing active suppression by other areas of the brain. The signal and mechanism releasing the arcuate nucleus from inhibition have been the subject of investigation for decades and remain incompletely understood. Leptin levels rise throughout childhood and play a part in allowing the arcuate nucleus to resume operation. If the childhood inhibition of the arcuate nucleus is interrupted prematurely by injury to the brain, it may resume pulsatile gonadotropin release and puberty will begin at an early age. RNA expression pattern Orthologs Human Mouse Entrez Ensembl Uniprot Refseq Location Pubmed search Leptin (from the Greek word leptos, meaning thin) is a 16 kDa protein hormone that plays a key role in regulating energy intake and energy expenditure, including the regulation (decrease) of appetite and (increase) of metabolism. ...


Neurons of the arcuate nucleus secrete gonadotropin releasing hormone (GnRH) into the blood of the pituitary portal system. These GnRH signals from the hypothalamus induce pulsed secretion of LH (and to a lesser degree, FSH) at roughly 1-2 hour intervals. In the years preceding physical puberty, these gonadotropin pulses occur primarily at night and are of very low amplitude, but as puberty approaches they can be detected during the day. By the end of puberty, there is little day-night difference in the amplitude and frequency of gonadotropin pulses.


An array of "autoamplification processes" increases the production of all of the pubertal hormones of the hypothalamus, pituitary, and gonads.


Regulation of adrenarche and its relationship to maturation of the hypothalamic-gonadal axis is not fully understood, and some evidence suggests it is a parallel but largely independent process coincident with or even preceding central puberty. Rising levels of adrenal androgens (termed adrenarche) can usually be detected between 6 and 11 years of age, even before the increasing gonadotropin pulses of hypothalamic puberty. Adrenal androgens contribute to the development of pubic hair (pubarche), adult body odor, and other androgenic changes in both sexes. The primary clinical significance of the distinction between adrenarche and gonadarche is that pubic hair and body odor changes by themselves do not prove that central puberty is underway for an individual child. Adrenarche refers to a stage of maturation of the cortex of the human adrenal glands. ... Androgen is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of masculine characteristics in vertebrates by binding to androgen receptors. ... Pubarche refers to the first appearance of pubic hair in a child. ... Bromhidrosis or body odor (also called bromidrosis, osmidrosis and ozochrotia) is the smell of bacteria growing on the body. ...


Hormonal changes in girls

As the amplitude of LH pulses increases, the theca cells of the ovaries begin to produce testosterone and smaller amounts of progesterone. Much of the testosterone moves into nearby cells called granulosa cells. Smaller increases of FSH induce an increase in the aromatase activity of these granulosa cells, which converts most of the testosterone to estradiol for secretion into the circulation. Progesterone is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy (supports gestation) and embryogenesis of humans and other species. ... A granulosa cell is a supporting cell for the developing female gamete in the ovary of mammals. ... Aromatase belongs to the group of cytochrome P450 enzymes (EC 1. ...


Rising levels of estradiol produce the characteristic estrogenic body changes of female puberty: growth spurt, acceleration of bone maturation and closure, breast growth, increased fat composition, growth of the uterus, increased thickness of the endometrium and the vaginal mucosa, and widening of the lower pelvis. The endometrium is the inner membrane of the mammalian uterus. ...


As the estradiol levels gradually rise and the other autoamplification processes occur, a point of maturation is reached when the feedback sensitivity of the hypothalamic "gonadostat" becomes positive. This attainment of positive feedback is the hallmark of female sexual maturity, as it allows the mid cycle LH surge necessary for ovulation. Ovulation is the process in the menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum (also known as an oocyte, female gamete, or casually, an egg) that participates in reproduction. ...


Levels of adrenal androgens and testosterone also increase during puberty, producing the typical androgenic changes of female puberty: pubic hair, other androgenic hair as outlined above, body odor, acne.


Growth hormone levels rise steadily throughout puberty. IGF1 levels rise and then decline as puberty ends. Growth finishes and adult height is attained as the estradiol levels complete closure of the epiphyses. Insulin-like growth factor 1 (IGF-1) is a polypeptide protein hormone similar in molecular structure to insulin. ... The word epiphysis can mean: The pineal gland, one of the endocrine glands. ...


Hormonal changes in boys

Early stages of male hypothalamic maturation seem to be very similar to the early stages of female puberty, though occurring about 1-2 years later.


LH stimulates the Leydig cells of the testes to make testosterone and blood levels begin to rise. For much of puberty, nighttime levels of testosterone are higher than daytime. Regularity of frequency and amplitude of gonadotropin pulses seems to be less necessary for progression of male than female puberty.


However, a significant portion of testosterone in adolescent boys is converted to estradiol. Estradiol mediates the growth spurt, bone maturation, and epiphyseal closure in boys just as in girls. Estradiol also induces at least modest development of breast tissue (gynecomastia) in a large proportion of boys. Boys who develop mild gynecomastia or even developing swellings under nipples during puberty are told the effects are temporary in some male teenagers due to high levels of Estradiol. Testosterone is a steroid hormone from the androgen group. ... Gynecomastia, or gynaecomastia, pronounced is the development of abnormally large mammary glands in males resulting in breast enlargement, which can sometimes cause secretion of milk. ... Gynecomastia, or gynaecomastia, pronounced is the development of abnormally large mammary glands in males resulting in breast enlargement, which can sometimes cause secretion of milk. ... Edema (BE: oedema, formerly known as dropsy) is swelling of any organ or tissue due to accumulation of excess fluid. ... This article is about the anatomical structure. ... Estradiol (17β-estradiol) (also oestradiol) is a sex hormone. ...


Another hormonal change in males takes place during the teenage years for most young men. At this point in a males life the testosterone levels slowly rise, and most of the effects are mediated through the androgen receptors by way of conversion dehydrotestosterone in target organs (especially that of the bowels). Consequently, there is a transformation that takes place and the processes in which human waste and urine are released by the body are reversed.


Historical shift

The age at which puberty occurs has dropped significantly since the 1840s.[32][33][34] Researchers refer to this drop as the 'secular trend'. From 1840 through 1950, in each decade there was a drop of four months in the average age of menarche among Western European female samples. In Norway, girls born in 1840 had their first menarche at average 17 years. In France in 1840 the average was 15.3 years. In England the 1840 average was 16.5 years for girls. In Japan the decline happened later and was then more rapid: from 1945 to 1975 in Japan there was a drop of 11 months per decade. 1840 is a leap year starting on Wednesday (link will take you to calendar). ... Year 1950 (MCML) was a common year starting on Sunday (link will display the full calendar) of the Gregorian calendar. ... For other uses, see England (disambiguation). ...


See also

Secondary sex characteristics are traits that distinguish the two sexes of a species, but that are not directly part of the reproductive system. ... Child sexuality refers to sexual feelings, behavior and development in children. ... Puberty is described as delayed when a boy or girl has passed the usual age of onset of puberty with no physical or hormonal signs that it is beginning. ... Menarche (IPA: ) is the first menstrual period, or first menstrual bleeding in the females of human beings. ... Gonadarche refers to the earliest gonadal changes of puberty. ... Pubarche refers to the first appearance of pubic hair in a child. ... Thelarche is the first stage of secondary (postnatal) breast development, usually occurring at the beginning of puberty in girls. ... Adrenarche refers to a stage of maturation of the cortex of the human adrenal glands. ... Precocious puberty means early puberty. ...

References

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  • Gungor, Neslihan; Arslanian SA (2002). "Chapter 21: Nutritional disorders: integration of energy metabolism and its disorders in childhood", in Sperling, MA ed.: Pediatric Endocrinology, 2nd ed., Philadelphia: Saunders, pp. 689–724. ISBN 0721695396. 
  • Marshall, William A.; Tanner, JM (1986). "Chapter 8: Puberty", in Falkner F, Tanner JM, eds.: Human Growth: A Comprehensive Treatise, 2nd ed., New York: Plenum Press, pp. 171–209. ISBN 0-306-41952-1. 
  • Rosenfield, Robert L. (2002). "Chapter 16: Female puberty and its disorders", in Sperling, MA ed.: Pediatric Endocrinology, 2nd ed., Philadelphia: Saunders, pp. 455–518. ISBN 0721695396. 
  • Styne, Dennis M. (2002). "Chapter 18: The testes: disorders of sexual differentiation and puberty in the male", in Sperling, MA ed.: Pediatric Endocrinology, 2nd ed., Philadelphia: Saunders, pp. 565–628. ISBN 0721695396. 
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  30. ^ Phil McKenna, "Childhood obesity brings early puberty for girls" "New Scientist" March 5, 2007 http://www.newscientist.com/article/dn11307-childhood-obesity-brings-early-puberty-for-girls.html
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  32. ^ Finley, Harry. "Average age at menarche in various cultures", Museum of Menstruation and Women's Health. Retrieved on 2007-08-02. 
  33. ^ Whincup, P H; J A Gilg, K Odoki, S J C Taylor, D G Cook (2001-05-05). "Age of menarche in contemporary British teenagers: survey of girls born between 1982 and 1986". BMJ 322: 1095-1096. doi:10.1136/bmj.322.7294.1095. 
  34. ^ "Girls maturing slightly earlier", BBC News, 2001-05-03. Retrieved on 2007-08-02. 

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Further reading

  • Ducros, A. and Pasquet, P. "Evolution de l'âge d'apparition des premières règles (ménarche) en France". Biométrie Humaine (1978), 13, 35–43.
  • Herman-Giddens ME, Slora EJ, Wasserman RC, et al. "Secondary sexual characteristics and menses in young girls seen in office practice: a study from the pediatric research in office settings network". Pediatrics, 1997; 99:501-12. Newer data suggesting we should be using lower age thresholds for evaluation.
  • Plant TM, Lee PA, eds. The Neurobiology of Puberty. Bristol: Society for Endocrinology, 1995. Proceedings of the latest (4th) International Conference on the Control of the Onset of Puberty, containing summaries of current theories of physiological control, as well as GnRH analog treatment.
  • Tanner JM, Davies PS. "Clinical longitudinal standards for height and weight velocity for North American children". J Pediatr 1985; 107:317-29. Highly useful growth charts with integrated standards for stages of puberty.

External links

is the 335th day of the year (336th in leap years) in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... Human Physiology is the science of the mechanical, physical, and biochemical functions of humans in good health, their organs, and the cells of which they are composed. ... Endocrinology is a branch of medicine dealing with disorders of the endocrine system and its specific secretions called hormones. ... Sexual reproduction is characterized by processes that pass a combination of genetic material to offspring, resulting in diversity. ... -1... The male reproductive system is a series of organs located outside of the body and around the pelvic region of a male. ... The human females reproductive system. ... Menstrual cycle In the female reproductive system, the menstrual cycle is a recurring cycle of physiologic changes that occurs in reproductive-age females. ... The estrous cycle (also oestrous cycle; originally derived from Latin oestrus) comprises the recurring physiologic changes that are induced by reproductive hormones in most mammalian placental females. ... Not to be confused with Mensuration. ... Menstrual cycle The follicular phase (or proliferative phase) is the phase of the estrous cycle, (or, in humans and great apes, the menstrual cycle) during which follicles in the ovary mature. ... Ovulation is the process in the menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum (also known as an oocyte, female gamete, or casually, an egg) that participates in reproduction. ... The luteal phase is the latter phase of the estrous cycle in animals. ... Gametogenesis is the creation of gametes by meiotic division of gametocytes into various gametes. ... Cross section of the epithelium of a seminiferous tubule showing various stages of spermatocyte development Spermatogenesis is the process by which male spermatogonia develop into mature spermatozoa. ... A Spermatogonium (plural: spermatogonia) is an intermediary male gametogonium (a kind of germ cell) in the production of spermatozoa. ... Spermatogenesis refers to the creation, or genesis, of sperm cells, which occurs in the male gonads or testes. ... The term spermatid refers to the haploid male germ cell that results from secondary spermatocyte division. ... For other uses, see Sperm (disambiguation). ... Oogenesis or rarely oögenesis is the creation of an ovum (egg cell). ... An oogonium is a female gametogonium. ... An oocyte or ovocyte is a female gametocyte or germ cell involved in reproduction. ... An ootid is a female gametid, as opposed to a male spermatid. ... A human ovum Sperm cells attempting to fertilize an ovum An ovum (plural ova) is a haploid female reproductive cell or gamete. ... A germ cell is part of the germline and is involved in the reproduction of organisms. ... A gamete (from Ancient Greek γαμετης; translated gamete = wife, gametes = husband) is a cell that fuses with another gamete during fertilization (conception) in organisms that reproduce sexually. ... This article is about sexual practices (i. ... It has been suggested that Duration of sexual intercourse be merged into this article or section. ... This article is about human physiological erection. ... Ejaculation is the ejecting of semen from the penis, and is usually accompanied by orgasm. ... An orgasm (sexual climax) is the conclusion of the plateau phase of the sexual response cycle, and may be experienced by both males and females. ... Insemination is the introduction of semen into the genital tract of a female. ... This article is about fertilisation in animals and plants. ... Fertility is the natural capability of giving life. ... Masturbation is the manual excitation of the sexual organs, most often to the point of orgasm. ... This article is about human pregnancy in biological females. ... This article does not cite any references or sources. ... This article is about prenatal development in humans. ... Female (left) and male Common Pheasant, illustrating the dramatic difference in both color and size, between the sexes Sexual dimorphism is the systematic difference in form between individuals of different sex in the same species. ... This article is about the development of sexual dimorphisms in humans. ... Menarche (IPA: ) is the first menstrual period, or first menstrual bleeding in the females of human beings. ... Adrenarche refers to a stage of maturation of the cortex of the human adrenal glands. ... Graph showing increased risk of Down Syndrome over time The maternal age effect describes the exponentially increasing risks of chromosomal abnormalities as a prospective mother ages. ... The paternal age effect describes the influence that a fathers age has on the chances of conferring a genetic defect to his offspring. ... The word menopause literally means the permanent physiological, or natural, cessation of menstrual cycles, from the Greek roots meno (month) and pausis (a pause, a cessation). ... Andropause is a medical phenomenon, similar to the female menopause, that can affect men between the ages of 40 and 55. ... A human ovum Sperm cells attempting to fertilize an ovum An ovum (plural ova) is a haploid female reproductive cell or gamete. ... Oviparous animals are animals that lay eggs, with little or no other embryonic development within the mother. ... Ovoviviparous animals develop within eggs that remain within the mothers body up until they hatch or are about to hatch. ... Poa alpina, a grass which shows vivipary: the seeds germinate while still attached to the mother plant. ... Reproductive endocrinology (RE) is a medical subspecialty that addresses hormonal functioning as it pertains to reproduction. ... The hypothalamic-pituitary-gonadal axis (also HPTA) is a way of referring to the combined effects of the hypothalamus, pituitary gland, and gonads as if these individual endocrine glands were a single entity. ... Andrology (from the Greek andros, man) is the medical specialty that deals with male health, particularly relating to the problems of the male reproductive system and urological problems that are unique to men. ... For other uses, see Hormone (disambiguation). ... This article is about biological human development. ... 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John Bowlby (February 26, 1907 - September 2, 1990) was a British psychoanalyst, notable for his interest in child development and his pioneering work in attachment theory. ... Mother and child Attachment theory is a psychological, evolutionary and ethological theory that provides a descriptive and explanatory framework for discussion of interpersonal relationships between human beings. ... This article needs additional references or sources for verification. ... // Psychosocial development as articulated by Erik Erikson describes eight developmental stages through which a healthily developing human should pass from infancy to late adulthood. ... Sigmund Freud (IPA: ), born Sigismund Schlomo Freud (May 6, 1856 – September 23, 1939), was an Austrian neurologist and psychiatrist who founded the psychoanalytic school of psychology. ... The concept of psychosexual development, as envisioned by Sigmund Freud at the end of the nineteenth and the beginning of the twentieth century, is a central element in the theory of psychology. ... Lawrence Kohlberg (October 25, 1927 – January 19, 1987) was an American psychologist. ... Kohlbergs stages of moral development are planes of moral adequacy conceived by Lawrence Kohlberg to explain the development of moral reasoning. ... Jean Piaget (August 9, 1896 – September 16, 1980) was a Swiss philosopher, natural scientist and developmental psychologist, well known for his work studying children, his theory of cognitive development and for his epistemological view called genetic epistemology. He created in 1955 the International Centre for Genetic Epistemology in Geneva and... // Although there is no general theory of cognitive development, one of the most historically influential theories was developed by Jean Piaget, a Swiss psychologist (1896–1980). ... Lev Vygotsky Lev Semenovich Vygotsky (Russian: Лев Семёнович Выготский) (November 17 (November 5 Old Style), 1896 – June 11, 1934) was a Soviet developmental psychologist and the founder of cultural-historical psychology. ... Cultural-historical psychology (the school of Vygotsky) - a trend in psychological research founded by Lev Vygotsky in the end of the 1920s and developed by his students and followers in Eastern Europe and worldwide. ...

  Results from FactBites:
 
Puberty Stages and Questions on Sexual Maturation of Teen Boys and Girls on MedicineNet.com (626 words)
Puberty is the time at which a growing boy or girl begins the process of sexual maturation.
Puberty involves a series of physical stages or steps that lead to the achievement of fertility and the development of the so-called secondary sex characteristics, the physical features associated with adult males and females (such as the growth of pubic hair).
Puberty usually occurs in girls between the ages of 10 and 14, while in boys it generally occurs later, between the ages of 12 and 16.
MedlinePlus Medical Encyclopedia: Puberty and adolescence (734 words)
Puberty is the time in which sexual and physical characteristics mature.
Adolescence is the period between puberty and adulthood.
During puberty, various endocrine glands produce hormones that cause body changes and the development of secondary sex characteristics.
  More results at FactBites »

 
 

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