Thyroid hormone metabolic effects

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

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... 

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. 

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). 

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. 

Van Birgelen APJM, Smit EA, Kampen IM, et al. 1995. Subchronic effects of 2,3,7,8-TCDD or PCBs on thyroid hormone metabolism use in risk assessment. Eur J Pharmacol 293 77-85. 

Endocrine Effects. Thyroid hormone metabolism is the result of a balance in iodine and selenium levels. Selenium is a component of the deiodinase enzymes, including the Type I and Type II iodothyronine 5 -deiodinases, which convert the prohormone thyroxine (T4) to the active form, triiodothyronine (T3) (Kohrle 1994 St Germain and Galton 1997). Iodine deficiency can lead to hypothyroidism but if iodine deficiency is accompanied by selenium deficiency, thyroid gland destruction may also occur (Contempre et al. 1991a Hofbauer et al. 1997). Supplementation of individuals deficient in both iodine and selenium with selenium produces a further decrease in thyroid function, but if selenium supplementation is preceded by normalization of iodine levels, normal thyroid function is restored (Contempre et al. 1991a, 1992). 

Calomme M, Vanderpas J, Francois B, et al. 1995. Effects of selenium supplementation on thyroid hormone metabolism in phenylketonuria subjects on a phenylalanine restricted diet. Biol Trace Elem Res 47 349-353. 

Contempre B, Duale NL, Dumont JE, et al. 1992. Effect of selenium supplementation on thyroid hormone metabolism in an iodine and selenium deficient population. Clin Endocrinol 36 579-583. 

FIGURE 3.7 CAR controls thyroid hormone metabolism, an effect involved in thyroid tumorigenesis and control of obesity. 

Klaassen, C. D. and Hood, A. M. (2001) Effects of microsomal enzyme inducers on thyroid follicular cell proliferation and thyroid hormone metabolism. Toxicol. Pathol. 29, 34-40. 

Beckett GJ, Nicol F, Rae PWH, Beech S, Guo Y and Arthur JR (1993) Effects of combined iodine and selenium deficiency on thyroid hormone metabolism in rats. Am J Clin Nutr 57 240-243. 

The first measurable effect of TSH on thyroid hormone metabolism is increased secretion, which is detectable within minutes. AU phases of hormone synthesis and secretion are eventually stimulated iodide uptake and organification, endocytosis, and proteolysis of thyroglobulin. There also is increased vascularity of the gland and hypertrophy and hyperplasia of thyroid cells. 

The dosage of 10 mg iodine/kg diet decreased serum T3 concentration significantly and increased (as a tendency) the serum concentration of rT3. In turkeys, higher doses of iodine, i.e., 20-100 times the recommendation/ requirement (Table 16.2) reduced the concentration ofT3 (Christensen and Ort, 1991) which indicates an unfavorable effect on thyroid hormone metabolism. 

Effect of propylthiouracil, iodothyronines, and other agents on thyroid hormone metabolism in human placenta. J. Clin. 

Wolf DC, Moore T, Abbott BD et al (2008) Comparative hepatic effects of perfluorooctanoic acid and WY 14,643 in PPAR-alpha knockout and wild-type mice. Toxicol Pathol 36(4) 632-639 Wu KM, Farrelly JG (2006) Preclinical development of new drugs that enhance thyroid hormone metabolism and clearance inadequacy of using rats as an animal model for predicting human risks in an END and NDA. Am J Ther 13(2) 141-144 Yang CF, Tan YS, Harkema JR et al (2009) Differential effects of peripubertal exposure to perfluorooctanoic acid on mammary gland development in C57BF6 and Balb/c mouse strains. Reprod Toxicol 27(3 ) 299-306... 

EFFECT OF SELENIUM DEFICIENCY ON THYROID HORMONE METABOLISM... 

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