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Encyclopedia > Endocrinology

Endocrinology is a branch of medicine dealing with disorders of the endocrine system and its specific secretions called hormones. Major endocrine glands. ... For other uses, see Hormone (disambiguation). ...

Contents

Function of endocrine organs, hormones and receptors

Hormones are molecules that act as signals from one type of cells to another. Most hormones reach their targets via the blood.


All multicellular organisms need coordinating systems to regulate and integrate the function of cells. Two mechanisms perform this function in higher animals: the nervous system and the endocrine system. The endocrine system acts through the release (generally into the blood) of chemical agents and is vital to the proper development and function of organisms. As Hadley notes,[1] the integration of developmental events such as proliferation, growth, and differentiation (including histogenesis and organogenesis) and the coordination of metabolism, respiration, excretion, movement, reproduction, and sensory perception depend on chemical cues, substances synthesised and secreted by specialised cells. An Introduction to Histogenesis Histogenesis is defined as the formation of tissues and organs from undifferentiated cells (Encarta Dictionary). ... Organogenesis is a stage of animal development where the ectoderm, endoderm, and mesoderm are formed. ... Structure of the coenzyme adenosine triphosphate, a central intermediate in energy metabolism. ... In animal physiology, respiration is the transport of oxygen from the ambient air to the tissue cells and the transport of carbon dioxide in the opposite direction. ... For other uses, see Reproduction (disambiguation) Reproduction is the biological process by which new individual organisms are produced. ...


Endocrinology is concerned with the study of the biosynthesis, storage, chemistry, and physiological function of hormones and with the cells of the endocrine glands and tissues that secrete them. Hormone is also the NATO reporting name for the Soviet/Russian Kamov Ka-25 military helicopter. ...


The endocrine system consists of several glands, in different parts of the body, that secrete hormones directly into the blood rather than into a duct system. Hormones have many different functions and modes of action; one hormone may have several effects on different target organs, and, conversely, one target organ may be affected by more than one hormone.


In the original 1902 definition by Bayliss and Starling (see below), they specified that, to be classified as a hormone, a chemical must be produced by an organ, be released (in small amounts) into the blood, and be transported by the blood to a distant organ to exert its specific function. This definition holds for most "classical" hormones, but there are also paracrine mechanisms (chemical communication between cells within a tissue or organ), autocrine signals (a chemical that acts on the same cell), and intracrine signals (a chemical that acts within the same cell).[2] A neuroendocrine signal is a "classical" hormone that is released into the blood by a neurosecretory neuron (see article on Neuroendocrinology). Paracrine signalling is a form of signalling in which the target cell is close to the signal releasing cell, and the signal chemical is broken down too quickly to be carried to other parts of the body. ... There are very few or no other articles that link to this one. ... redirect Template:Db-reason synaptophysin ... Neuroendocrinology is the study of the interactions between the nervous system and the endocrine system. ...


Hormones act by binding to specific receptors in the target organ. As Baulieu notes, a receptor has at least two basic constituents:

  • a recognition site, to which the hormone bind
  • an effector site, which precipitates the modification of cellular function.[3]

Between these is a "transduction mechanism" in which hormone binding induces allosteric modification that, in turn, produces the appropriate response.


Chemical classes of hormones

Amine hormones: norepinephrine and triiodothryonine
Amine hormones: norepinephrine and triiodothryonine
Steroid hormones: cortisol and vitamin D3

Griffin and Ojeda identify three different classes of hormone based on their chemical composition:[4] Image File history File links Diagramatic representation of the chemical structure of two amine hormones (norepinephrine and T3) Drawn my myself in Microsoft Word 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 Diagramatic representation of the chemical structure of two amine hormones (norepinephrine and T3) Drawn my myself in Microsoft Word 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 Diagramatic representation of the chemical structure of two steroid hormones; one with an intact steroid nucleus (cortisol) and one without (vitamin D3) Drawn by myself in Microsoft Word File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to... Image File history File links Diagramatic representation of the chemical structure of two steroid hormones; one with an intact steroid nucleus (cortisol) and one without (vitamin D3) Drawn by myself in Microsoft Word File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to...


Amines

Amines, such as norepinephrine, epinephrine, and dopamine, are derived from single amino acids, in this case tyrosine. Thyroid hormones such as 3,5,3’-triiodothyronine (T3) and 3,5,3’,5’-tetraiodothyronine (thyroxine, T4) make up a subset of this class because they derive from the combination of two iodinated tyrosine amino acid residues. Norepinephrine (INN)(abbr. ... Adrenaline redirects here. ... For other uses, see Dopamine (disambiguation). ...


Peptide and protein

Peptide hormones and protein hormones consist of three (in the case of thyrotropin-releasing hormone) to more than 200 (in the case of follicle-stimulating hormone) amino acid residues and can have molecular weights as large as 30,000. All hormones secreted by the pituitary gland are peptide hormones, as are leptin from adipocytes, ghrelin from the stomach, and insulin from the pancreas. Wikipedia does not yet have an article with this exact name. ... Thyrotropin-releasing hormone (TRH), also called thyrotropin-releasing factor (TRF) or protirelin, is a tripeptide hormone that stimulates the release of thyroid-stimulating hormone and prolactin by the anterior pituitary. ... Follicle stimulating hormone Follicle stimulating hormone (FSH) is a hormone synthesised and secreted by gonadotropes in the anterior pituitary gland. ... 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. ... Ghrelin is a hormone produced by P/D1 cells lining the acer of the human stomach that stimulate appetite. ... Not to be confused with inulin. ... The pancreas is a gland organ in the digestive and endocrine systems of vertebrates. ...


Steroid

Steroid hormones are converted from their parent compound, cholesterol. Mammalian steroid hormones can be grouped into five groups by the receptors to which they bind: glucocorticoids, mineralocorticoids, androgens, estrogens, and progestagens. Steroid hormones are steroids which act as hormones. ... Cholesterol is a sterol (a combination steroid and alcohol). ... The name glucocorticoid derives from early observations that these hormones were involved in glucose metabolism. ... Mineralocorticoids is a class of steroids characterised by their similarity to aldosterone and their influence on salt and water metabolism. ... 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. ... Estrogens (or oestrogens) are a group of steroid compounds that function as the primary female sex hormone. ... Progestagens (also spelled progestogens or gestagens) are hormones similar in effect to progesterone, the only natural progestagen. ...


History and key discoveries of endocrinology

The study of endocrinology began when Berthold noted that castrated cockerels did not develop combs and wattles or exhibit overtly male behaviour.[5] He found that replacement of testes back into the abdominal cavity of the same bird or another castrated bird resulted in normal behavioural and morphological development, and he concluded (erroneously) that the testes secreted a substance that "conditioned" the blood that, in turn, acted on the body of the cockerel. In fact, one of two other things could have been true: that the testes modified or activated a constituent of the blood or that the testes removed an inhibitory factor from the blood. It was not proven that the testes released a substance that engenders male characteristics until it was shown that the extract of testes could replace their function in castrated animals. Pure, crystalline testosterone was isolated in 1935.[6] Testosterone is a steroid hormone from the androgen group. ...


Although most of the relevant tissues and endocrine glands had been identified by early anatomists, a more humoral approach to understanding biological function and disease was favoured by classical thinkers such as Aristotle, Hippocrates, Lucretius, Celsus, and Galen, according to Freeman et al,[7] and these theories held sway until the advent of germ theory, physiology, and organ basis of pathology in the 19th century... For other uses, see Aristotle (disambiguation). ... For other uses, see Hippocrates (disambiguation). ... Lucretius Titus Lucretius Carus (c. ... Celsus (Greek: ) was a 2nd century Greek philosopher and opponent of Christianity. ... For other uses, see Galen (disambiguation). ...


In 1902 Bayliss and Starling performed an experiment in which they observed that acid instilled into the duodenum caused the pancreas to begin secretion, even after they had removed all nervous connections between the two.[8] The same response could be produced by injecting extract of jejunum mucosa into jugular vein, showing that some factor in the mucosa was responsible. They named this substance "secretin" and coined the term hormone for chemicals that act in this way. In anatomy of the digestive system, the duodenum is a hollow jointed tube about 25-30 cm long connecting the stomach to the jejunum. ... The pancreas is a gland organ in the digestive and endocrine systems of vertebrates. ... Secretin is a peptide hormone produced in the S cells of the duodenum. ...


von Mering and Minkowski made the observation in 1889 that removing the pancreas surgically led to an increase in blood sugar, followed by a coma and eventual death—symptoms of diabetes mellitus. In 1922, Banting and Best realized that homogenizing the pancreas and injecting the derived extract reversed this condition.[9] The hormone responsible, insulin, was not discovered until Frederick Sanger sequenced it in 1953. The pancreas is a gland organ in the digestive and endocrine systems of vertebrates. ... For the disease characterized by excretion of large amounts of very dilute urine, see diabetes insipidus. ... Not to be confused with inulin. ...


Neurohormones were first identified by Otto Loewi in 1921.[10] He incubated a frog's heart (innervated with its vagus nerve attached) in a saline bath, and left in the solution for some time. The solution was then used to bathe a non-innervated second heart. If the vagus nerve on the first heart was stimulated, negative inotropic (beat amplitude) and chronotropic (beat rate) activity were seen in both hearts. This did not occur in either heart if the vagus nerve was stimulated. The vagus nerve was adding something to the saline solution. The effect could be blocked using atropine, a known inhibitor to heart vagal nerve stimulation. Clearly, something was being secreted by the vagus nerve and affecting the heart. The "vagusstuff" (as Loewi called it) causing the myotropic effects was later identified to be acetylcholine and norepinephrine. Loewi won the Nobel Prize for his discovery. A neurohormone is any hormone produced by neurosecretory cells, usually in the brain. ... Otto Loewi (June 3, 1873 – December 25, 1961) was a Austrian-German-American pharmacologist. ... The vagus nerve (also called pneumogastric nerve or cranial nerve X) is the tenth of twelve paired cranial nerves, and is the only nerve that starts in the brainstem (within the medulla oblongata) and extends, through the jugular foramen, down below the head, to the abdomen. ... Inotropic: Affecting the force of muscle contraction. ... Chronotropic effects (from chrono-, meaning time) are those that change the heart rate. ... The chemical compound acetylcholine, often abbreviated as ACh, was the first neurotransmitter to be identified. ... Norepinephrine (INN)(abbr. ...


Recent work in endocrinology focuses on the molecular mechanisms responsible for triggering the effects of hormones. The first example of such work being done was in 1962 by Earl Sutherland. Sutherland investigated whether hormones enter cells to evoke action, or stayed outside of cells. He studied norepinephrine, which acts on the liver to convert glycogen into glucose via the activation of the phosphorylase enzyme. He homogenized the liver into a membrane fraction and soluble fraction (phosphorylase is soluble), added norepinephrine to the membrane fraction, extracted its soluble products, and added them to the first soluble fraction. Phosphorylase activated, indicating that norepinephrine's target receptor was on the cell membrane, not located intracellularly. He later identified the compound as cyclic AMP (cAMP) and with his discovery created the concept of second-messenger-mediated pathways. He, like Loewi, won the Nobel Prize for his groundbreaking work in endocrinology.[11] This article does not cite any references or sources. ... Glucose (Glc), a monosaccharide (or simple sugar), is an important carbohydrate in biology. ... Phosphorylase is an enzyme that catalyzes the production of glucose phosphate from glycogen and inorganic phosphate. ... Structure of cAMP cAMP represented in three ways, the left with sticks-representation, the middle with structure formula, and the right with space filled representation. ...


Endocrinology as a profession

Although every organ system secretes and responds to hormones (including the brain, lungs, heart, intestine, skin, and the kidney), the clinical specialty of endocrinology focuses primarily on the endocrine organs, meaning the organs whose primary function is hormone secretion. These organs include the pituitary, thyroid, adrenals, ovaries, testes, and pancreas. The human brain In animals, the brain (enkephale) (Greek for in the skull), is the control center of the central nervous system, responsible for behavior. ... The heart and lungs (from an older edition of Grays Anatomy) The lung is an organ belonging to the respiratory system and interfacing to the circulatory system of air-breathing vertebrates. ... The heart and lungs, from an older edition of Grays Anatomy. ... In anatomy, the intestine is the segment of the alimentary canal extending from the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine. ... For other uses, see Skin (disambiguation). ... The kidneys are the organs that filter wastes (such as urea) from the blood and excrete them, along with water, as urine. ... Located at the base of the skull, the pituitary gland is protected by a bony structure called the sella turcica. ... In mammals, the adrenal gland (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... // 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. ... The pancreas is a gland organ in the digestive and endocrine systems of vertebrates. ...


An endocrinologist is a doctor who specializes in treating disorders of the endocrine system, such as diabetes, hyperthyroidism, and many others (see list of diseases below). This article is about the disease that features high blood sugar. ... Hyperthyroidism (or overactive thyroid gland) is the clinical syndrome caused by an excess of circulating free thyroxine (T4) or free triiodothyronine (T3), or both. ...


Work

The medical specialty of endocrinology involves the diagnostic evaluation of a wide variety of symptoms and variations and the long-term management of disorders of deficiency or excess of one or more hormones.


The diagnosis and treatment of endocrine diseases are guided by laboratory tests to a greater extent than for most specialties. Many diseases are investigated through excitation/stimulation or inhibition/suppression testing. This might involve injection with a stimulating agent to test the function of an endocrine organ. Blood is then sampled to assess the changes of the relevant hormones or metabolites. An endocrinologist needs extensive knowledge of clinical chemistry and biochemistry to understand the uses and limitations of the investigations. This article does not cite any references or sources. ... Clinical chemistry (also known as clinical biochemistry, chemical pathology or pure blood chemistry) is the area of pathology that is generally concerned with analysis of bodily fluids. ... Biochemistry (from Greek: , bios, life and Egyptian kēme, earth[1]) is the study of the chemical processes in living organisms. ...


A second important aspect of the practice of endocrinology is distinguishing human variation from disease. Atypical patterns of physical development and abnormal test results must be assessed as indicative of disease or not. Diagnostic imaging of endocrine organs may reveal incidental findings called incidentalomas, which may or may not represent disease. Medical imaging is the process by which physicians evaluate an area of the subjects body that is not normally visible. ... In medicine, an incidentaloma is a tumor (-oma) found by coincidence (incidental) without clinical symptoms and suspicion. ...


Endocrinology involves caring for the person as well as the disease. Most endocrine disorders are chronic diseases that need life-long care. Some of the most common endocrine diseases include diabetes mellitus, hypothyroidism and the metabolic syndrome. Care of diabetes, obesity and other chronic diseases necessitates understanding the patient at the personal and social level as well as the molecular, and the physician–patient relationship can be an important therapeutic process. Medicine In medicine, a persistent and lasting condition is said to be chronic (from Greek chronos). ... This article is about the disease that features high blood sugar. ... This article or section does not cite its references or sources. ...


Apart from treating patients, many endocrinologists are involved in clinical science and medical research, teaching, and hospital management. Clinical science is the practical study of medical principles or investigations using controlled procedures to evaluate results. ... Medical research (or experimental medicine) is basic research and applied research conducted to aid the body of knowledge in the field of medicine. ... In education, teachers are those who teach students or pupils, often a course of study or a practical skill. ...


Training

There are roughly 7,000 to 8,000 endocrinologists in the United States. Endocrinologists are specialists of internal medicine or pediatrics. Reproductive endocrinologists deal primarily with problems of fertility and menstrual function—often training first in obstetrics. Most qualify as an internist, pediatrician, or gynecologist for a few years before specializing, depending on the local training system. In the U.S. and Canada, training for board certification in internal medicine, pediatrics, or gynecology after medical school is called residency. Further formal training to subspecialize in adult, pediatric, or reproductive endocrinology is called a fellowship. Typical training for a North American endocrinologist involves 4 years of college, 4 years of medical school, 3 years of residency, and 3 years of fellowship. Adult endocrinologists are board certified by the American Board of Internal Medicine (ABIM) in Endocrinology, Diabetes and Metabolism. Doctors of internal medicine (internists) are medical specialists who focus on adult medicine and have had special study and training focusing on the prevention and treatment of adult diseases. ... This article is about the branch of medicine. ... Fertility is the natural capability of giving life. ... Internal medicine is concerned with the diagnosis and treatment of internal diseases, that is, those that affect internal organs or the body as a whole. ... Pediatrics (also spelled paediatrics or pædiatrics) is the branch of medicine that deals with the medical care of infants and children. ... The shamefulness associated with the examination of female genitalia has long inhibited the science of gynaecology. ... This article is about the branch of medicine. ... The shamefulness associated with the examination of female genitalia has long inhibited the science of gynaecology. ... Pediatric endocrinology is a medical subspecialty dealing with variations of physical growth and sexual development in childhood, as well as diabetes and other disorders of the endocrine glands. ... The American Board of Internal Medicine (ABIM) is a non-profit, independent physician organization in the U.S. that certifies physicians who practice in internal medicine and its subspecialties. ...


Professional organizations

In North America the principal professional organizations of endocrinologists include The Endocrine Society,[12] the American Association of Clinical Endocrinologists,[13] the American Diabetes Association,[14] the Lawson Wilkins Pediatric Endocrine Society,[15] and the American Thyroid Association.[16]


In the United Kingdom, the Society for Endocrinology[17] and the British Society for Paediatric Endocrinology and Diabetes[18] are the main professional organisations. The European Society for Paediatric Endocrinology[19] is the largest international professional association dedicated solely to paediatric endocrinology. There are numerous similar associations around the world.


Patient education

Because endocrinology encompasses so many conditions and diseases, there are many organizations that provide education to patients and the public. The Hormone Foundation is the public education affiliate of The Endocrine Society and provides information on all endocrine-related conditions. Other educational organizations that focus on one or more endocrine-related conditions include the American Diabetes Association, National Osteoporosis Foundation, Human Growth Foundation, American Menopause Foundation, Inc., and Thyroid Foundation of America. Established in 1997 by The Endocrine Society as its public education affiliate, The Hormone Foundation serves as a resource for physicians, patients, and the public by promoting the prevention, treatment and cure of hormone-related conditions through outreach and education. ... The Endocrine Society is a professional, international medical organization in the field of endocrinology and metabolism, founded in 1916. ... The American Diabetes Association, or the ADA, is an American health organization providing diabetes research, information and advocacy. ... The National Osteoporosis Foundation (NOF) is an American voluntary health organization dedicated to osteoporosis and bone health. ...


Diseases

See main article at Endocrine diseases

A disease due to a disorder of the endocrine system is often called a "hormone imbalance", but is technically known as an endocrinopathy or endocrinosis. Among the hundreds of endocrine diseases (or endocrinological diseases) are: Adrenal disorders: Adrenal insufficiency Addisons disease Congenital adrenal hyperplasia (adrenogenital syndrome) Mineralocorticoid deficiency Conns syndrome Cushings syndrome Pheochromocytoma Adrenocortical carcinoma Glucose homeostasis disorders: Diabetes mellitus Hypoglycemia Idiopathic hypoglycemia Insulinoma Metabolic bone disease: Osteoporosis Osteitis deformans (Pagets...


See also

Pediatric endocrinology is a medical subspecialty dealing with variations of physical growth and sexual development in childhood, as well as diabetes and other disorders of the endocrine glands. ... Neuroendocrinology is the study of the interactions between the nervous system and the endocrine system. ... Reproductive endocrinology (RE) is a medical subspecialty that addresses hormonal functioning as it pertains to reproduction. ... For other uses, see Hormone (disambiguation). ...

References

  1. ^ Hadley ME. Endocrinology 5th ed. London: Prentice –Hall International (UK) Ltd, 2000.
  2. ^ Nussey S, Whitehead S. Endocrinology: An integrated approach. Oxford: BIOS Scientific Publishers Ltd., 2001.
  3. ^ Baulieu EE. Hormones: From molecules to disease Baulieu, E-E. and Kelly, P.A., (eds) Paris: Hermann, 1990.
  4. ^ Griffin JE, Ojeda SR. Textbook of Endocrine Physiology 4th ed. New York: Oxford University Press, 2000.
  5. ^ Berthold AA. Transplantation der Hoden Arch. Anat. Phsiol. Wiss. Med. 1849;16:42-6.
  6. ^ David K, Dingemanse E, Freud J et al. Uber krystallinisches mannliches Hormon aus Hoden (Testosteron) wirksamer als aus harn oder aus Cholesterin bereitetes Androsteron. Hoppe Seylers Z Physiol Chem 1935;233:281.
  7. ^ Freeman ER, Bloom DA, McGuire JE. A Brief History of Testosterone. J Urol 2001;165:371-373.
  8. ^ Bayliss WM, Starling EH. The mechanism of pancreatic secretion. J Physiol 1902;28:325–352.
  9. ^ Bliss, M. J.J.R. Macleod and the discovery of insulin. Quart. J. Exp. Physiol. Wiss. Med. 1989;16:42-6.
  10. ^ Loewi, O. Uebertragbarkeit der Herznervenwirkung. Pfluger's Arch. ges Physiol. 1921;189:239-42.
  11. ^ Sutherland, E. Studies on the mechanisms of hormone action. Science 1972;177:401-8.
  12. ^ Endo-society.org
  13. ^ AACE.com
  14. ^ Diabetes.org
  15. ^ lwpes.org
  16. ^ Thyroid.org
  17. ^ endocrinology.org
  18. ^ bsped.org.uk
  19. ^ Eurospe.org

External links

  • Endocrinology (British online textbook)
  • Endotext (American online textbook)
  • On-Line Endocrinology Journal Club (via JournalReview.org)
  • Useful Endocrinology Resources for Residents
  • Endocrinology journals from Elsevier
  • MeSH Endocrinology
  • The Hormone Foundation

Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ...

Societies and associations


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Endocrinology is a branch of medicine dealing with disorders of the endocrine system and its specific secretions called hormones.
Endocrinology is concerned with the study of the biosynthesis, storage, chemistry, and physiological function of hormones and with the cells of the endocrine glands and tissues that secrete them.
The medical specialty of endocrinology involves the diagnostic evaluation of a wide variety of symptoms and variations and the long-term management of disorders of deficiency or excess of one or more hormones.
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