[Selenium deficiency and thyroid hormone metabolism and function]

Type I 5'-deiodinase is a Se-containing enzyme. If Se is deficient, the deiodinase activity would be inhibited, the level of circulation T4 will be elevated, and the concentration T3 in peripheral tissues will be decreased. Se deficiency will also accelerate the iodine depletion of thyroid and may even exacerbate some detrimental effects of iodine deficiency. Possibly Se deficiency is involved in the occurrence and development of iodine deficient disorders. Keshan disease, with Se deficiency as the major cause, was also observed a change of thyroid hormone metabolism. The change of respiratory enzyme activities in myocardium of Keshan disease is in the way somewhat like that of hypothyroidism caused by iodine deficiency. The metabolic change of thyroid hormone after Se deficiency or iodine deficiency may be related to the occurrence of Keshan disease.