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Thyroxine
ThyroxineThyroxine is the principal hormone produced by the thyroid gland. It promotes protein synthesis (blending) and growth, and also helps regulate the body's metabolism. Thyroid Stimulating HormonesThyroxine is produced by the thyroid gland in a very complex way. When the blood's thyroxine level is low, the brain's hypothalamus (the part of the brain that regulates body functions) produces a thyrotropin-releasing hormone. This stimulates the pituitary gland to produce thyrotropin. Thyrotropin is a thyroid-stimulating hormone (TSH) that excites the thyroid gland. When the blood's thyroxine level is high, the hypothalamus releases a hormone that inhibits TSH production. HyperthyroidismHyperthyroidism is a condition caused by an overactive thyroid. The syndrome can cause weight loss, nervousness, and protruding eyes. Called Graves's disease, it was first identified by Irish physician Robert James Graves (1796-1853). Treating Underactive GlandsGerman chemist Eugen Baumann (1846-1896) was the first researcher to treat underactive thyroids using extracts made from animal thyroid glands. In 1914 American biochemist Edward Kendall isolated and used the crystalline form of the hormone which was later named thyroxine. In 1926 the British chemist C. R. Harington (1897-1972) determined thyroxine's exact structure and synthesized it out of materials in a laboratory. Treating Overactive GlandsToday, overactive glands can be treated with medication, removed surgically, or destroyed by radiation. When the gland is removed or destroyed the patient must always take thyroid hormones as replacement therapy. Hormone therapy is also used for underactive glands. The first widely-used test to measure peoples' thyroid levels was developed in the 1930s by American biochemist Evelyn B. Man (1904-1992). Called the protein-bound iodine test, it soon showed that many "demented" patients in mental hospitals (those having deteriorated mental capabilities) actually had underactive thyroid glands. Treatments with thyroxine helped many of these patients regain normal mental abilities. Doctors now routinely evaluate an infants' thyroid function by testing blood from newborn babies' umbilical cords. This allows correction of any thyroid gland problem before mental or physical damage occurs. |
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"Thyroxine." Medical Discoveries. 1997. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. "Thyroxine." Medical Discoveries. 1997. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1G2-3498100219.html "Thyroxine." Medical Discoveries. 1997. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1G2-3498100219.html |
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thyroxine
thyroxine , substance secreted by the thyroid gland . The hormone thyroxine forms by combining the amino acid tyrosine with iodine. Complexed to a protein, it is stored in the follicle stems between thyroid cells. Thyroxine enters into the bloodstream complexed to another protein, plasma globulin. Thyroxine increases the number and activity of mitochondria in cells by binding to the cells' DNA, increasing the basal metabolic rate. Administration of thyroid hormones, such as thyroxine, causes an increase in the rate of carbohydrate metabolism and a rise in the rate of protein synthesis and breakdown. The hormone, which excites the nervous system and leads to increased activity of the endocrine system , remains active in the body for more than a month. Thyroxine activity is controlled by thyrotropin , a substance released from the pituitary gland . Conversely, thyroxine regulates the effect of thyrotropin by feedback inhibition, i.e., high levels of thyroxine depress the rate of thyrotropin secretion. Synthetically prepared thyroxine is used clinically in the treatment of thyroid gland deficiency diseases in adults and in the treatment of cretinism in children. |
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"thyroxine." The Columbia Encyclopedia, 6th ed.. 2008. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. "thyroxine." The Columbia Encyclopedia, 6th ed.. 2008. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1E1-thyroxin.html "thyroxine." The Columbia Encyclopedia, 6th ed.. 2008. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-thyroxin.html |
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thyroxine
thy·rox·ine / [unvoicedth]īˈräksēn; -sin/ (also thyroxin / -sin/ ) • n. Biochem. the main hormone, C15H11NO4I4, produced by the thyroid gland, acting to increase metabolic rate and so regulating growth and development. |
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"thyroxine." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. "thyroxine." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O999-thyroxine.html "thyroxine." The Oxford Pocket Dictionary of Current English. 2009. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O999-thyroxine.html |
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thyroxine
thyroxine An iodinated amino acid, formed in the thyroid gland from the proteolysis of thyroglobulin. It is the major hormone of this gland and exerts a positive control of the basal metabolic rate of virtually all tissues and organs in the body.
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MICHAEL ALLABY. "thyroxine." A Dictionary of Zoology. 1999. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. MICHAEL ALLABY. "thyroxine." A Dictionary of Zoology. 1999. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O8-thyroxine.html MICHAEL ALLABY. "thyroxine." A Dictionary of Zoology. 1999. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O8-thyroxine.html |
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thyroxine
thyroxine Hormone secreted by the thyroid gland. It contains iodine and helps regulate the rate of metabolism; it is essential for normal growth and development.
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"thyroxine." World Encyclopedia. 2005. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. "thyroxine." World Encyclopedia. 2005. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O142-thyroxine.html "thyroxine." World Encyclopedia. 2005. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-thyroxine.html |
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thyroxine
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"thyroxine." A Dictionary of Biology. 2004. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. "thyroxine." A Dictionary of Biology. 2004. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O6-thyroxine.html "thyroxine." A Dictionary of Biology. 2004. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O6-thyroxine.html |
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thyroxine
thyroxine (T4) (th'y-roks-een) n. see thyroid hormone.
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"thyroxine." A Dictionary of Nursing. 2008. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. "thyroxine." A Dictionary of Nursing. 2008. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O62-thyroxine.html "thyroxine." A Dictionary of Nursing. 2008. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O62-thyroxine.html |
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thyroxine
thyroxine One of the thyroid hormones.
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DAVID A. BENDER. "thyroxine." A Dictionary of Food and Nutrition. 2005. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. DAVID A. BENDER. "thyroxine." A Dictionary of Food and Nutrition. 2005. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O39-thyroxine.html DAVID A. BENDER. "thyroxine." A Dictionary of Food and Nutrition. 2005. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O39-thyroxine.html |
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