Dietary Selenium Intake Modulates Thyroid Hormone and Energy Metabolism in Men

Abstract

Most studies of selenium and thyroid hormone have used sodium selenite in rats. However, rats regulate thyroid hormone differently, and selenite, which has unique pharmacologic activities, does not occur in foods. We hypothesized that selenium in food would have different effects in humans. Healthy men were fed foods naturally high or low in selenium for 120 d while confined to a metabolic research unit. Selenium intake for all subjects was 47 microg/d (595 nmol/d) for the first 21 d, and then changed to either 14 (n = 6) or 297 (n = 5) microg/d (177 nmol/d or 3.8 micromol/d) for the remaining 99 d, causing significant changes in blood selenium and glutathione peroxidase. Serum 3,3',5-triiodothyronine (T3) decreased in the high selenium group, increased in the low selenium group, and was significantly different between groups from d 45 onward. A compensatory increase of thyrotropin occurred in the high selenium group as T3 decreased. The changes in T3 were opposite in direction to those reported in rats, but were consistent with other metabolic changes. By d 64, the high selenium group started to gain weight, whereas the low selenium group began to lose weight, and the weight changes were significantly different between groups from d 92 onward. Decreases of serum T3 and compensatory increases in thyrotropin suggest that a subclinical hypothyroid response was induced in the high selenium group, leading to body weight increases. Increases of serum T3 and serum triacylglycerol accompanied by losses of body fat suggest that a subclinical hyperthyroid response was induced in the low selenium group, leading to body weight decreases.

Effects of high selenium and fat supplementation on growth performance and thyroid hormones concentration of broilers

“…Although the effects of Se deficiency on thyroid hormone metabolism have been studied extensively in a number of animals [5,6] including chicken [7], very little is known about the influence of excess Se on thyroid hormone metabolism and selenoenzyme activities. In humans, Se supplementation led to variable results, depending on the Se status of the examined population group, extending from non to substantial changes in thyroid function [8][9][10][11][12]. Under this context, the form of Se (inorganic or organo-Se compounds) may also affect body Se reserves built and bioavailability [13,14].…”

Analysis of iodine and its species in animal tissues

“…[37] To investigate the bioavailability and distribution of iodine in animal tissues, it was necessary to prepare methods for the determination of the total iodine content as well as for the description of iodine speciation in animal tissues. These methods comprise considerable sample preparation, determination of total iodine concentration by ICP-MS, and determination of iodine species using several modes of LC-ICP-MS coupling.…”

Mercury and Selenium in Blood and Epidermis of Bottlenose Dolphins (Tursiops truncatus) from Sarasota Bay, FL: Interaction and Relevance to Life History and Hematologic Parameters

“…Other selenoproteins in blood include type I iodothyronine deiodinase, which converts thyroxine (T4), to the more active 3,3 0 ,5-triiodothyronine (T3). This conversion and its consequent influence on metabolic rate are linked to Se availability (Hawkes and Keim, 2003). In addition to a strong affinity for Se, Hg binds readily to sulfhydryls; thus Hg concentration may relate to numerous blood parameters reflecting oxidative and metabolic status.…”