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14-September-2008 12:50:32 - Endocrinology Endocrinology is a branch of medicine dealing with disorders of the endocrine system and its specific secretions called hormones. Contents 1 Function of endocrine organs, hormones and receptors 2 Chemical classes of hormones 2.1 Amines 2.2 Peptide and protein 2.3 Steroid 3 History and key discoveries of endocrinology 4 Endocrinology as a profession 4.1 Work 4.2 Training 4.3 Professional organizations 5 Patient education 6 Diseases 7 Endocrinologist in Popular Culture 8 See also 9 References 10 External links 10.1 Societies and associations 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. 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 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. 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 binds 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 Steroid hormones: cortisol and vitamin D3 Griffin and Ojeda identify three different classes of hormone based on their chemical composition:4 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. 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. 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. History and key discoveries of endocrinology The study of endocrinology began in China. The Chinese were isolating sex and pituitary hormones from human urine and using them for medicinal purposes by 200 BC5. They used many complex methods, such as sublimation. 6 Eventually, when Berthold noted that castrated cockerels did not develop combs and wattles or exhibit overtly male behaviour, European endocrinology began however, it should be noted that the Chinese anticipated the science by over 1500 years. 7 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 1935.8 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,9 and these theories held sway until the advent of germ theory, physiology, and organ basis of pathology in the 19th century. In medieval Persia, Avicenna 980-1037 provided a detailed account on diabetes mellitus in The Canon of Medicine c. 1025, describing the abnormal appetite and the collapse of sexual functions and he documented the sweet taste of diabetic urine. Like Aretaeus of Cappadocia before him, Avicenna recognized a primary and secondary diabetes. He also described diabetic gangrene, and treated diabetes using a mixture of lupine, trigonella fenugreek, and zedoary seed, which produces a considerable reduction in the excretion of sugar, a treatment which is still prescribed in modern times. Avicenna also described diabetes insipidus very precisely for the first time, though it was later Johann Peter Frank 1745-1821 who first differentiated between diabetes mellitus and diabetes insipidus.10 In the 12th century, al-Jurjani, another Persian physician, provided the first description of Graves' disease after noting the association of goitre and exophthalmos in his Thesaurus of the Shah of Khwarazm, the major medical dictionary of its time.1112 Al-Jurjani also established an association between goitre and palpitation.10 The disease was later named after Irish doctor Robert James Graves,13 who described a case of goiter with exophthalmos in 1835. The German Karl Adolph von Basedow also independently reported the same constellation of symptoms in 1840, while earlier reports of the disease were also published by the Italians Giuseppe Flajani and Antonio Giuseppe Testa, in 1802 and 1810 respectively,14 and by the English physician Caleb Hillier Parry a friend of Edward Jenner in the late 18th century.15 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.16 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. 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.17 The hormone responsible, insulin, was not discovered until Frederick Sanger sequenced it in 1953. Neurohormones were first identified by Otto Loewi in 1921.18 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. 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.19 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. 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. 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. 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. 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. Apart from treating patients, many endocrinologists are involved in clinical science and medical research, teaching, and hospital management. Training There are roughly 70,000 to 80,000 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. Professional organizations In North America the principal professional organizations of endocrinologists include The Endocrine Society,20 the American Association of Clinical Endocrinologists,21 the American Diabetes Association,22 the Lawson Wilkins Pediatric Endocrine Society,23 and the American Thyroid Association.24 In the United Kingdom, the Society for Endocrinology25 and the British Society for Paediatric Endocrinology and Diabetes26 are the main professional organisations. The European Society for Paediatric Endocrinology27 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. 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. Endocrinologist in Popular Culture Dr. Lisa Cuddy , a character on the television show House M.D. See also Pediatric endocrinology Neuroendocrinology Reproductive endocrinology hormone References ^ Hadley, Mac E. 2000. Endocrinology, 5th ed., Englewood Cliffs, N.J: Prentice Hall. ISBN 0-13-080356-1. ^ Nussey S, Whitehead S 2001. Endocrinology: An Integrated Approach. ISBN 1-85996-252-1. ^ Kelly, Paul; Baulieu, Etienne-Emile 1990. Hormones: from molecules to disease. Paris: Hermann. ISBN 2-7056-6030-5. ^ Ojeda, Sergio R.; Griffin, James Bennett 2000. Textbook of endocrine physiology, 4th ed., Oxford Oxfordshire: Oxford University Press. ISBN 0-19-513541-5. ^ Temple, Robert. The Genius of China.pp. 141, 142. ISBN 9781594772177. ^ Temple, Robert. The Genius of China.p. 142. ISBN 9781594772177 ^ Berthold AA. Transplantation der Hoden Arch. Anat. Phsiol. Wiss. Med. 1849;16:42-6. ^ 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. ^ Freeman ER, Bloom DA, McGuire EJ 2001. A brief history of testosterone. J. Urol. 165 2: 371-3. doi:10.1097/00005392-200102000-00004. PMID 11176375. ^ a b Nabipour, I. 2003, Clinical Endocrinology in the Islamic Civilization in Iran, International Journal of Endocrinology and Metabolism 1: 43-45 44-5 ^ Basedow's syndrome or disease at Who Named It - the history and naming of the disease ^ Ljunggren, J. G. August 10, 1983, Who was the man behind the syndrome: Ismail al-Jurjani, Testa, Flagani, Parry, Graves or Basedow? Use the term hyperthyreosis instead, Lakartidningen 8032-33: 2902, PMID 6355710 ^ Robert James Graves at Who Named It ^ Giuseppe Flajani at Who Named It ^ Hull G 1998. Caleb Hillier Parry 1755-1822: a notable provincial physician. Journal of the Royal Society of Medicine 91 6: 335-8. PMID 9771526. ^ Bayliss WM, Starling EH. The mechanism of pancreatic secretion. J Physiol 1902;28:325-352. ^ Bliss M 1989. J. J. R. Macleod and the discovery of insulin. Q J Exp Physiol 74 2: 87-96. PMID 2657840. ^ Loewi, O. Uebertragbarkeit der Herznervenwirkung. Pfluger's Arch. ges Physiol. 1921;189:239-42. ^ Sutherland EW 1972. Studies on the mechanism of hormone action. Science 177 47: 401-8. PMID 4339614. ^ Endo-society.org ^ AACE.com ^ Diabetes.org ^ lwpes.org ^ Thyroid.org ^ endocrinology.org ^ bsped.org.uk ^ Eurospe.org External links Endocrinology British online textbook Endotext American online textbook Useful Endocrinology Resources for Residents Endocrinology journals from Elsevier MeSH Endocrinology The Hormone Foundation Societies and associations Endocrine Society American Association of Clinical Endocrinologists American Diabetes Association Lawson Wilkins Pediatric Endocrine Society Society for Endocrinology Society for Behavioral Neuroendocrinology British Society for Paediatric Endocrinology Diabetes v d e Health science Medicine Specialties and subspecialties Surgery Anesthesiology · Cardiac surgery · Cardiothoracic surgery · General surgery · Neurosurgery · Oral and maxillofacial surgery · Orthopedic surgery Hand surgery · Otolaryngology ENT · Pediatric surgery · Plastic surgery · Surgical oncology · Thoracic surgery · Transplant surgery · Trauma surgery · Urology · Vascular surgery Internal medicine Cardiology · Endocrinology · Gastroenterology · Geriatrics · Hematology · Hepatology · Infectious diseases · Intensive care medicine · Nephrology · Oncology · Proctology · Pulmonology · Rheumatology Diagnostic Clinical laboratory sciences Cellular pathology, Clinical chemistry, Hematology, Clinical microbiology, Clinical immunology, Transfusion medicine · Radiology Interventional radiology, Nuclear Medicine · Pathology Anatomical, Clinical · Clinical neurophysiology Other specialties Allergy and immunology · Dermatology · Disaster medicine · Emergency medicine · General practice · Neurology · Obstetrics and gynaecology Fertility medicine · Andrology · Reproductive medicine · Occupational medicine · Ophthalmology · Palliative care · Pediatrics · Physical medicine and rehabilitation Physiatry · Preventive medicine Public health · Psychiatry · Sleep medicine Other Epidemiology · History of medicine · Hospital medicine · Medical education · Medical genetics · Medical school · Osteopathic medicine · Pharmacy · Physician MD and DO · Physician Assistant · Sports medicine · Medical fiction v d e Human anatomy, endocrine system: endocrine glands Hypothalamic/ pituitary axes Thyroid axis Thyroid gland Parafollicular cell, Thyroid epithelial cell, Thyroid isthmus, Lobes of thyroid gland, Pyramid of thyroid Parathyroid gland Oxyphil cell, Chief cell Adrenal axis Adrenal gland Gonadal axis Testes - Ovaries - Corpus luteum Pineal gland Pinealocyte Islets of pancreas Alpha cell - Beta cell - Delta cell - PP cell - Epsilon cell v d e Endocrinology Fields Pediatric endocrinology Psychoneuroendocrinology Neuroendocrinology Reproductive endocrinology Other Blood sugar regulation Calcium metabolism Endocrine glands v d e Endocrine pathology: endocrine diseases E00-35, 240-259 Pancreas/ glucose metabolism Diabetes mellitus types: type 1, type 2, MODY, complications: coma, angiopathy, ketoacidosis, nephropathy, neuropathy, retinopathy Hypoglycemia - Hyperinsulinism - Zollinger-Ellison syndrome - insulin receptor Rabson-Mendenhall syndrome - Insulin resistance Hypothalamic/ pituitary axes Pituitary Hyperpituitarism Acromegaly, Hyperprolactinaemia, SIADH Hypopituitarism Sheehan's syndrome, Kallmann syndrome, Growth hormone deficiency, Diabetes insipidus Adiposogenital dystrophy - Empty sella syndrome - Pituitary apoplexy - ACTH deficiency Thyroid Hypothyroidism Iodine deficiency, Cretinism, Congenital hypothyroidism, Goitre, Myxedema Hyperthyroidism Graves disease, Toxic multinodular goitre, Teratoma with thyroid tissue or Struma ovarii Thyroiditis De Quervain's thyroiditis, Hashimoto's thyroiditis, Riedel's thyroiditis Euthyroid sick syndrome - Thyroid hormone resistance - Thyroid nodule Parathyroid Hypoparathyroidism Pseudohypoparathyroidism - Hyperparathyroidism Primary, Secondary, Tertiary Adrenal Adrenocortical hyperfunction: Cushing's syndrome Nelson's syndrome, Pseudo-Cushing's syndrome - Hyperaldosteronism Conn syndrome, Bartter syndrome CAH Lipoid, 3β, 11β, 17α, 21α Adrenal insufficiency Addison's disease, Waterhouse-Friderichsen syndrome - Hypoaldosteronism Gonads ovarian Polycystic ovary syndrome, Premature ovarian failure testicular 5-alpha-reductase deficiency, 17-beta-hydroxysteroid dehydrogenase deficiency general Hypogonadism, Delayed puberty, Precocious puberty Other Androgen insensitivity syndrome - Autoimmune polyendocrine syndrome - Carcinoid syndrome - Gigantism - Short stature Laron syndrome, Psychogenic dwarfism - Multiple endocrine neoplasia 1, 2 - Progeria - Woodhouse-Sakati syndrome - thymus Abscess of thymus, Thymus hyperplasia see also congenital, neoplasia Retrieved from http://en..org/wiki/Endocrinology Categories: Endocrine system | Endocrinology | Subjects taught in medical school Views Article Discussion this page History Personal tools Log in / create account Navigation Main page Contents Featured content Current events Random article Search Go Search Interaction Community portal Recent changes Contact Donate to Help Toolbox What links here Related changes Upload file Special pages Printable version Permanent link Cite this page Languages العربية বাংলা Bosanski БългарÑ?ки Català Česky Dansk Deutsch Español Euskara Français Hrvatski Ã?slenska Italiano עברית ქáƒ?რთული Lietuvių Magyar Nederlands नेपाली 日本語 ‪Norsk bokmÃ¥l‬ Polski Português Română РуÑ?Ñ?кий Shqip SlovenÄ?ina SlovenÅ¡Ä?ina СрпÑ?ки / Srpski Svenska Türkçe УкраїнÑ?ька ä¸æ–‡ This page was last modified on 6 September 2008, at 14:41
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