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Encyclopedia > Menarche

Menarche (IPA: /məˈnɑrki/) is the first menstrual period, or first menstrual bleeding in the females of human beings. From both social and medical perspectives it is often considered the central event of female puberty, as it signals the possibility of fertility. Timing of menarche is influenced by both genetic and environmental factors, especially nutritional status. The average age of menarche has declined over the last century but the magnitude of the decline and the factors responsible remain subjects of contention. The average age of menarche in the United States is about 12 years and 6 months. Menstrual cycle The menstrual cycle is a recurring cycle of physiologic changes that occurs in the females of several mammals, including human beings and other apes. ... Human beings are defined variously in biological, spiritual, and cultural terms, or in combinations thereof. ... Puberty refers to the process of physical changes by which a childs body becomes an adult body capable of reproduction. ... Fertility is the natural capability of giving life. ...

Contents

Physiologic aspects

Menarche as part of puberty

Menarche is the culmination of a series of physiological and anatomic processes of puberty, described in more detail in that article: Puberty refers to the process of physical changes by which a childs body becomes an adult body capable of reproduction. ...

  • Attainment of a sufficient body mass (typically 17% body fat PMID 3117838).
  • Disinhibition of the GnRH pulse generator in the arcuate nucleus of the hypothalamus
  • Secretion of estrogen by the ovaries in response to pituitary hormones.
  • Over an interval of about 2 to 3 years, estrogen stimulates growth of the uterus (as well as height growth, breast growth, widening of the pelvis, and increased regional adipose tissue).
  • Estrogen stimulates growth and vascularity of the endometrium, the lining of the uterus.
  • Fluctuations of hormone levels can result in changes of adequacy of blood supply to parts of the endometrium.
  • Death of some of the endometrial tissue from these hormone or blood supply fluctuations leads to deciduation, a sloughing of part of the lining with some blood flow from the vagina.

A specific hormonal signal for menarche is not known; menarche as a discrete event is thought to be the relatively chance result of the gradual thickening of the endometrium induced by rising but fluctuating pubertal estrogen. Gonadotropin Releasing Hormone (GnRH) is a peptide hormone responsible for the release of FSH and LH from the anterior pituitary. ... 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). ... Estriol. ... // For ovary as part of plants see ovary (plants) An ovary is an egg-producing reproductive organ found in female organisms. ... Located at the base of the skull, the pituitary gland is protected by a bony structure called the sella turcica. ... Norepinephrine A hormone (from Greek όρμή - to set in motion) is a chemical messenger from one cell (or group of cells) to another. ... This article is about female reproductive anatomy. ... For other uses, see Breast (disambiguation). ... The pelvis (pl. ... 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 endometrium is the inner membrane of the mammalian uterus. ... 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. ...


The menstruum, or "flow", consists of a combination of fresh and clotted blood with endometrial tissue. The initial flow of menarche is usually brighter red than mature menstrual flow. It is often scanty in amount and may be very brief, even a single instance of "spotting". Like other menses, menarche may be accompanied by abdominal cramping. Abdominal pain can be one of the symptoms associated with transient disorders or serious disease. ...


Menarche and fertility

In most girls, menarche does not signal that ovulation has occurred. Studies of American girls suggest that the average interval between menarche and ovulation is several months. Irregular, anovulatory menses commonly occur for 1-2 years or more before regular ovulation is established. 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. ...


Regular ovulation is usually indicated by predictable and consistent intervals between menses, predictable and consistent durations of menses, and predictable and consistent patterns of flow (e.g., heaviness or cramping). Continuing ovulation typically requires a body fat content of at least 22%. An anthropological term for this state of potential fertility is nubility. Anthropology (from Greek: ἀνθρωπος, anthropos, human being; and λόγος, logos, knowledge) is the study of humanity. ... Nubility is the state of being marriageable. ...


On the other hand, not every girl follows the typical pattern and some girls have ovulated before the first menstruation. Although unlikely, it is possible for a girl engaging in sexual intercourse shortly before her menarche would occur to conceive and become pregnant, delaying her menarche until after the birth. This would be a rare exception to the widely held assumption that a woman cannot become pregnant until after menarche. It has been suggested that Duration of sexual intercourse be merged into this article or section. ... The term conception can refer to more than one meaning: Concept Fertilisation This is a disambiguation page — a navigational aid which lists pages that might otherwise share the same title. ... This article is about human pregnancy in biological females. ...


Effects of stress and social environment on timing of menarche

Some of the least understood environmental influences on timing of puberty are social and psychological. Nearly all of the research on these effects 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. In most of these studies menarche was specifically examined, assuming it to be a valid "proxy" for the more general process of puberty. In comparison with the effects of genetics, nutrition, and general health, social influences are small, shifting timing by a few months rather than years. The most important part of a child's psychosocial environment is the family.


Some of the aspects of family structure and function reported to be independently associated with earlier menarche:

  • The increased incidence of childhood obesity (reaching a body weight of 100 lbs or 45kg appears to be an important "trigger" for the very young reaching menarche--both estrogen and progesterone are fat-soluble hormones).
  • Absence of father from the home from early childhood
  • High conflict family relationships
  • Living in an urban environment

Some of the aspects of family structure and function reported to be independently associated with later menarche:

  • Larger family size
  • Warmer, closer or more positive relationship with biological father
  • Warmer, more supportive, low stress family environment
  • Having a number of older sisters

Other research has focused on the effect of childhood stress on timing of puberty, especially female. Stress is a vague term and studies have examined conditions ranging from family tensions or conflict to wartime refugee status with threat to physical survival. The more dire social conditions have been found to be associated with delay of maturation, an effect that may be compounded by dietary inadequacy. There is more uncertainty and mixed evidence as to whether milder degrees of stress or early-life undernutrition can accelerate puberty in girls as would be predicted by life history theory and demonstrated in many other mammals. In medical terms, stress is the disruption of homeostasis through physical or psychological stimuli. ... Life history theory is a method of analysis in animal and human biology, psychology, and especially evolutionary sociobiology which postulates that many of the physiological traits and behaviors of individuals may be best understood in relation to the key maturational and reproductive characteristics that define the life course. ...


The understanding of these environmental effects is incomplete and the following observations and cautions are relevant:

  • Mechanisms of these social effects are unknown, though a variety of physiological processes, including pheromones, have been suggested based on animal research.
  • 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.
  • Despite the small magnitude of effect, 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.

Fanning honeybee exposes Nasonov gland (white-at tip of abdomen) releasing pheromone to entice swarm into an empty hive A pheromone is a chemical that triggers an innate behavioural response in another member of the same species. ... 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. ...

Changes over time in the average age of menarche

There were few systematic studies of timing of menarche before the latter half of the 20th century. Most older estimates of average timing of menarche were based on observation of a small homogeneous population not necessarily representative of the larger population, or based on recall by adult women, which is also susceptible to various forms of error. Most sources agree that average age of menarche in girls in modern societies has declined, though the reasons and the degree remain subjects of controversy. There have been claims of a 2 to 2.5 year decline from about 1900 to the 1960s, but the best North American surveys reported only a 2-3 month decline from the mid-1970s to the mid-1990s. This is commonly attributed to larger body size and earlier average attainment of sufficient body fat, but other factors such as environmental exposure to chemicals that mimic estrogen or the urbanization or "sexualization" of Western society have also been offered by some.


Less than 10% of US girls start to menstruate before 11 years of age, and 90% of all US girls are menstruating by 13.75 years of age, with a median age of 12.43 years. This age at menarche is not significantly different (0.34 years earlier) than that reported for US girls in 1973. Age at menarche for non-Hispanic black girls was significantly earlier than that of white girls at 10%, 25%, and 50% of those who had attained menarche, whereas Mexican American girls were only significantly earlier than the white girls at 25%. [1]


Cultural aspects of menarche

Menarche is celebrated in many cultures around the world as a rite of passage, a time to recognize that a girl is moving into womanhood. For other uses, see Rite of passage (disambiguation). ...


Rites of passage

Some cultures have in past centuries have had rites of passage for a girl experiencing menarche.

  • In the United States, rites of passage are rare since girls are taught to keep aspects of sexual development private. However, some families celebrate by giving the girl a card of congratulations, or even a candlelight ceremony.
  • The Navajo Indians have a celebration called kinaalda (kinn-all-duh). Girls run footraces to show strength. A cornmeal pudding is made for the tribe to taste. The girls who experience menarche wear special clothes and style their hair like the Navajo goddess "Changing Woman".
  • The Nootka Indians thought menarche was a time for a physical strength test. The girl is taken out to sea and left there. She is to swim back and when she returns to the shore of the village, she is cheered.
  • The Mescalero Apaches consider their menarche celebration the most important. Each year, an 8-day-long ceremony is celebrated in honor of each girl who began their period that year. The first 4 days include of feasting and dancing. Boy singers recount the history of the tribe each evening. The other four days are a private celebration where girls have a private ceremony, reflecting on passing into womanhood.
  • In Australia, the Aborigines treated a girl to "love magic". The women teach her of the female powers and the physical changes marking womanhood.
  • When a Japanese girl has her first period, the family celebrates by eating red colored rice and beans.
  • The Ulithi (oo-lith-ee) tribe of Micronesia call a girl's menarche kufar (koo-faar). She goes to a menstrual house where the women bathe her and recite spells. The girl will go back to the menstrual house when her next period comes.
  • In Nigeria in the Tiv tribe, four lines are cut in her abdomen, being thought to make her a woman and more fertile.
  • Sri Lanka notes the time and day. An astrologer is contacted, who studies the star's alignment at the noted moment. This is done to predict the girl's future. Her house is prepared for a ritual bathing, where the girl is scrubbed all over by the women of the family. She then is dressed in white. Printed invitations for a party are sent out, where the girl receives money and special gifts.
  • In rural India a girl who has reached puberty is given a ceremonial bath, decked with ornate jewels and garments and the girl's kith and kin are all invited for a ceremony where it is announced that the girl has come of age and celebrations follow. The tradition is quite non-existent in urban India, although some families still hold on to this fast-disappearing tradition.

The Navajo (also Navaho) people of the southwestern United States call themselves the Diné (pronounced ), which roughly means the people. They speak the Navajo language, and many are members of the Navajo Nation, an independent government structure which manages the Navajo reservation in the Four Cs area of the United... Languages Several hundred Indigenous Australian languages (many extinct or nearly so), Australian English, Australian Aboriginal English, Torres Strait Creole, Kriol Religions Primarily Christian, with minorities of other religions including various forms of Traditional belief systems based around the Dreamtime Related ethnic groups see List of Indigenous Australian group names Indigenous...

Medical aspects of menarche

When menarche occurs, it confirms that the girl has had a gradual estrogen-induced growth of the uterus, especially the endometrium, and that the "outflow tract" from the uterus, through the cervix to the vagina, is open. Estriol. ... This article is about female reproductive anatomy. ... The endometrium is the inner membrane of the mammalian uterus. ... The cervix (from Latin neck) is the lower, narrow portion of the uterus where it joins with the top end of the vagina. ... 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. ...


In very rare instances, menarche may occur at an unusually early age, preceding thelarche and other signs of puberty. This is termed isolated premature menarche, but other causes of bleeding must be investigated and excluded. Growth is usually normal. [2] Isolated premature menarche is rarely the first manifestation of precocious puberty. Thelarche is the first stage of secondary (postnatal) breast development, usually occurring at the beginning of puberty in girls. ... Precocious puberty means early puberty. ...


When menarche has failed to occur for more than 3 years after thelarche, or past 16 years of age, the delay is referred to as primary amenorrhea. Amenorrhoea (BE), amenorrhea (AmE), or amenorrhœa, is the absence of a menstrual period in a woman of reproductive age. ...


See also

Puberty refers to the process of physical changes by which a childs body becomes an adult body capable of reproduction. ... 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. ... Precocious puberty means early puberty. ... 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. ... Pubarche refers to the first appearance of pubic hair in a child. ... Gonadarche refers to the earliest gonadal changes of puberty. ... Menstrual cycle The menstrual cycle is a recurring cycle of physiologic changes that occurs in the females of several mammals, including human beings and other apes. ... Lina Medina (born September 27, 1933 in Paurange, Peru) gave birth at the age of 5 years, 7 months and 21 days and is the youngest confirmed mother in medical history. ...

References

  1. ^ Chumlea WC, Schubert CM, Roche AF, Kulin HE, Lee PA, Himes JH, Sun SS (2003 Jan). "Age at menarche and racial comparisons in US girls., 2005. PMID 12509562". Lifespan Health Research Center, Department of Community Health, Wright State University, School of Medicine, Dayton, Ohio, USA. 
  2. ^ R. Stanhope, C. Traggiai (2006). Isolated Menarche. Precocious Puberty (Complete, Partial). Retrieved on 2006-11-26.

Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 330th day of the year (331st in leap years) in the Gregorian calendar. ...

Further reading

  • Quinlan, R. (2003). Father-Absence, Parental Care & Female Reproductive Development. Evolution & Human Behavior. 24(6): 376-390. Full text

External links

  • Mark Hanson, P. Gluckman. Evolution, development and timing of puberty, Trends in Endocrinology & Metabolism, January 2006.
  • [1] Discusses some of the social influences

  Results from FactBites:
 
NodeWorks - Encyclopedia: Menarche (211 words)
Menarche refers to the first menstrual period, or first menstrual bleeding, as a female's body progresses through the changes of puberty.
When menarche occurs, it confirms that the female has had a gradual estrogen-induced growth of the uterus, especially the endometrium, and that the "outflow tract" from the uterus, through the cervix to the vagina, is open.
Menarche and subsequent menstrual periods (menses) may occur without ovulation, but there have been rare instances of ovulation preceding menarche by 1–2 weeks.
  More results at FactBites »

 
 

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