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United States Department of Agriculture

Agricultural Research Service

Title: The Effects of Dietary Selenium on Thyroid Hormones, Energy Metabolism, Semen Quality, and Immune Funciton in Healthy Men

item Hawkes, Chris
item Keim, Nancy
item Kelley, Darshan

Submitted to: International Symposium on Selenium in Biology and Medicine
Publication Type: Abstract Only
Publication Acceptance Date: August 18, 1996
Publication Date: N/A

Technical Abstract: Eleven healthy men (20-45 y) were fed a diet of foods naturally high (356 mcg/d, n=5) or low (13 mcg/d, n=6) in Se for 14 wk. Erythrocyte Se decreased 28% in the low Se group (LSe) and increased 65% in the high Se group (HSe). Serum triiodothyronine (T3) decreased 16% in HSe and increased 16% in LSe by the 3rd wk of Se treatment and remained different. T4 and rT3 did not change. Tyroid stimulating hormone increased 32% in HSe relative to LSe. Despite adjustment of energy intake to maintain body weight, by the 6th we HSe started to gain weight relative to LSe. LSe lost 0.5 kg and HSe gained 0.8 kg. LSe lost 1.6 kg of fat and their serum triglycerides transiently increased 53% relative to HSe, reflecting the known effects of T3 on fat metabolism. Although the change in T3 was opposite to that observed in animals, it was consistent with the change in body weight. Semen volume decreased 51% and sperm motlity decreased 42% in nHSe relative to LSe. No other semen parameters were affected by Se, although the sperm count and mean forward velocity decreased in both groups. Granulocyte and total white blood cell (WBC) counts were increased 6% and 11% in LSe, respectively. Lymphocyte proliferation in response to T and B cell mitogens, and numbers of helper, suppressor and natural killer cells were not affected by dietary Se, nor were antibody responses to Dt and influenza vacciens nor delayed type hypersensitivity skin responses. These results demonstrate that the effects of Se on thyroid hormones in humans are different from aniamls, presumably because of differing sensitivities of the 3 Se-deiodinases to dietary Se between species. The decrease semen quality and increased WBC counts may be secondary to the T3 effects, since hypothroid men and hyperthyroid animals show similar changes

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