SELENIUM GLUTATHIONE-PEROXIDASE ACTIVITIES AND THYROID FUNCTIONS IN HUMAN INDIVIDUALS

At least two enzymes are involved in metabolism of thyroid hormones. G SHPx protects thyrocyte from high H2O2 levels that are required for io dination of prohormones to form T4 in thyroid cell. Type I iodothyroni ne 5'-deiodinase (5'-D) catalyzes the deiodination of L-thyroxin (T4) to the biologically active thyroid hormone 3,3'-5-triiodothyronine (T- 3) in liver, in kidney and in thyroid tissues. Circulating thyroid hor mones, plasma Se levels, GSHPx activities in platelets and in plasma w ere investigated in 29 human individuals with increased thyroid mass. PIXE was applied to measure Se in 1 mi of plasma because we supposed p atients were in a marginal carential status for Se. Plasma Se concentr ations were compared with those of normal individuals. Correlation stu dies between plasma Se level and both GSHPx activities were carried ou t as well as between platelets and plasma GSHPx activities to verify t he hypothesis of a marginal Se deficiency in patients. Significance of circulating thyroid hormones levels will be discussed.