Thyroid hormone metabolism

Brouwer, A. (1991). Role of biotransformation in PCB-induced alterations in vitamin A and thyroid hormone metabolism in laboratory and wildlife species. Biochemical Society Transactions 19, 731-737. 

TCDD also causes thyroid tumours in male rats. This has been shown to proceed through a mechanism that involves altered thyroid hormone metabolism and consequent increases in feedback mechanisms, TSH (thyroid stimulating hormone), which results in a chronic proliferative stimulation of thyroid follicular cells. 

An adequate dietary intake of iodine is essential to prevent hypothyroidism. In many areas of the world, dietary iodine intake is insufficient and must be supplemented. There is another element in which a dietary intake may be insufficient that is also associated with thyroid hormone metabolism. This element is... 

B. Selenium in the form of selenocysteine is required for three enzymes that remove iodide from thyroid hormones. There are no signihcant areas in which dietary intake of sodium or potassium are problems. Fluorine deficiency is not associated with thyroid hormone metabolism. 

Byme JJ, Carbone JP, Hanson EA. 1987. Hypothyroidism and abnormalities in the kinetics of thyroid hormone metabolism in rats treated chronically with polychlorinated biphenyl and polybrominated biphenyl. Endocrinology 21 520-527. 

Ohnhaus EE, Studer H. A link between liver microsomal enzyme activity and thyroid hormone metabolism in man. Br J Clin Pharmacol 1983 15(l) 71-6. 

Thyroid function tests are often altered by somatropin because of increased conversion of T4 to T3, but this is clinically insignificant at low doses (SEDA-21, 453). One child with Prader-Willi syndrome had a fall in serum thyroxine concentration during somatropin therapy and needed thyroxine replacement (33). Hypothyroidism developed in 11 of 46 growth hormone-deficient children treated with somatropin (34). Prior abnormalities in hypothalamic-pituitary function and alterations in thyroid hormone metabolism, probably both, contributed to the high incidence of hypothyroidism, which was similar to that in previous studies. 

The effect of beta-adrenoceptor antagonists on thyroid hormone metabolism is unlikely to play a significant role... 

Wiersinga WM, Trip MD. Amiodarone and thyroid hormone metabolism. Postgrad Med J 1986 62(732) 909-14. 

Laurberg P, Andersen S, Karmisholt J. Cold adaptation and thyroid hormone metabolism. Horrn Metab Res. 2005 37 545-549. 

Thiourea derivatives are known for their anti-thyroid effects due to inhibition of thyroid peroxidase [1], Two thiourea compounds especially, have found wide application in the treatment of patients with hyperthyroidism, i.e., PTU and 2-mer-capto-l-methylimidazole (methimazole). It was soon recognized, however, that while methimazole only blocks thyroid hormone synthesis PTU has an additional effect on thyroid hormone metabolism [13]. These clinical findings have been confirmed in vitro showing that PTU, but not methimazole, is a potent inhibitor of the type I deiodinase [5-8]. Structure-activity studies of thiourea analogues [44,45] have... 

The low T3 syndrome is induced by a decrease in the production of plasma T3 as well as the clearance of plasma rT3 and is observed in several clinical situations such as starvation, systemic illness and the use of certain drugs [115]. In fasting [70] and illness [108] the abnormal thyroid hormone metabolism appears to result from a defective liver uptake and, therefore, a decreased supply of T4 and rT3 for intracellular deiodination. In other conditions such as treatment with PTU or propranolol [116], the defect appears localized in the type I deiodinase itself leading to a decline in T3 formation and rT3 breakdown. 

Selenium This metal is an essential trace element that functions as a component of enzymes involved in antioxidant protection and thyroid hormone metabolism. The existence of a number of selenoproteins has been demonstrated. In several intra- and extracellular glutathione peroxidases and iodothyronine... 

J. R. Arthur, F. Nicol, G. J. Beckett, The role of selenium in thyroid hormone metabolism and effects of selenium deficiency on thyroid hormone and iodine metabolism, Biol. Trace Elem. Res., 33 (1992), 37-42. 

Arthur J. R. and Beckett G. T. (1989) Selenium deficiency and thyroid hormone metabolism. In Selenium in Biology and Medicine (ed. A. Wendell). Springer, Berlin, pp. 90-95. 

Hoppner, W., and Sieiz, H -J. (1989) Effect of thyroid hormones on glucokinase gene transcription in rat liver, f, Biol, Client- 264, 20643-20647-Kaptein, E. M. (1996). Thyroid hormone metabolism and thyroid diseases in chronic renal failure. Ernlocr. Rev. 17, 45-65... 

The effect of beta-adrenoceptor antagonists on thyroid hormone metabolism is unlikely to play a significant role in their use in hyperthyroidism. Since D-propranolol has similar effects on thyroxine metabolism to those seen with the racemic mixture, membrane-stabilizing activity may be involved (176). 

The major functions of selenium can be attributed to its antioxidative properties and its role in the regulation of thyroid hormone metabolism. Selenium is important as a nutritional factor, and the US Food and Nutrition Board s Committee on Dietary Allowances has, perhaps somewhat arbitrarily, proposed a recommended daily intake of 50-200 micrograms/day. 

Kaptein, E. M. (1996). Thyroid hormone metabolism and thyroid diseases in chronic renal failure. Endocr. Rev. 17,45-63. 

Corssmit EP, Heyligenberg R, Endert E, et al. Acute effects of interferon-a administration on thyroid hormone metabolism in healthy men. J Clin Endocrinol Metab 1996 80 3140-4. 

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