Selenium status is positively associated with bone mineral density in healthy aging European men

Objective It is still a matter of debate if subtle changes in selenium (Se) status affect thyroid function tests (TFTs) and bone mineral density (BMD). This is particularly relevant for the elderly, whose nutritional status is more vulnerable. Design and Methods We investigated Se status in a cohort of 387 healthy elderly men (median age 77 yrs; inter quartile range 75-80 yrs) in relation to TFTs and BMD. Se status was determined by measuring both plasma selenoprotein P (SePP) and Se. Results The overall Se status in our population was low normal with only 0.5% (2/387) of subjects meeting the criteria for Se deficiency. SePP and Se levels were not associated with thyroid stimulating hormone (TSH), free thyroxine (FT4), thyroxine (T4), triiodothyronine (T3) or reverse triiodothyronine (rT3) levels. The T3/T4 and T3/rT3 ratios, reflecting peripheral metabolism of thyroid hormone, were not associated with Se status either. SePP and Se were positively associated with total BMD and femoral trochanter BMD. Se, but not SePP, was positively associated with femoral neck and ward's BMD. Multivariate linear analyses showed that these associations remain statistically significant in a model including TSH, FT4, body mass index, physical performance score, age, smoking, diabetes mellitus and number of medication use. Conclusion Our study demonstrates that Se status, within the normal European marginally supplied range, is positively associated with BMD in healthy aging men, independent of thyroid function. Thyroid function tests appear unaffected by Se status in this population

Fetal tissues are exposed to biologically relevant free thyroxine concentrations during early phases of development

Maternal hypothyroxinemia in early pregnancy is often associated with irreversible effects on neuropsychomotor development. To evaluate fetal tissue exposure to maternal thyroid hormones up to midgestation, we measured total T-4 and free T-4 (FT4), T-3, rT(3), TSH, and possible binding proteins in first trimester coelomic and amniotic fluids and in amniotic fluid and fetal serum up to 17 wk. Samples were obtained before interruption of maternal-fetal connections. The concentrations in fetal compartments of T-4 and T-3 are more than 100-fold lower than those in maternal serum, and their biological relevance for fetal development might be questioned. We found, however, that in all fetal fluids the concentrations of T-4 available to developing tissues, namely FT4, reach values that are at least one third of those biologically active in their euthyroid mothers. FT4 levels in fetal fluids are determined by both their T-4-binding protein composition and the T-4 or FT4 in maternal serum. The binding capacity is determined ontogenically, is independent of maternal thyroid status, and is far in excess of the T-4 in fetal fluids. Thus, the availability of FT4 for embryonic and fetal tissues would decrease in hypothyroxinemic women, even if they were euthyroid. A decrease in the availability of FT4, a major precursor of intracellular nuclear receptor-bound T-3, may result in adverse effects on the timely sequence of developmental events in the human fetus. These findings ought to influence our present approach to maternal hypothyroxinemia in early pregnancy regardless of whether TSH is increased or whether overt or subclinical hypothyroidism is detected

Effect of selenium supplementation on thyroid hormone metabolism in an iodine and selenium deficient population

OBJECTIVE: Severe selenium deficiency has been documented in northern Zaïre, already known as one of the most iodine deficient regions in the world and characterized by a predominance of the myxoedematous form of cretinism. This has been attributed to the double deficiency of essential trace elements. A short selenium supplementation programme was conducted in this area to evaluate the effects of a selenium supplementation on thyroid diseases. DESIGN: Placebo or selenium 50 micrograms as selenomethionine was administered once daily for 2 months. Blood and urine samples were collected before and after supplementation. PATIENTS: Fifty-two healthy schoolchildren from northern Zaire. MEASUREMENT: Selenium status, thyroid function and urinary iodide were determined. RESULTS: After 2 months of selenium supplementation, mean +/- SD serum T4 decreased from 73.1 +/- 45.4 to 48.3 +/- 23.7 nmol/l (P less than 0.001), serum FT4 from 11.8 +/- 6.7 to 8.4 +/- 4.1 pmol/l (P less than 0.01), and serum rT3 from 124 +/- 115 to 90 +/- 72 pmol/l (P less than 0.05), without significant change in serum T3 and serum TSH. CONCLUSION: Deiodinase type I which has been shown to be a seleno-enzyme could account for the changes in thyroid hormones in our subjects. Our data show that selenium plays a definite role in thyroid hormone metabolism in humans. Selenium could be an important cofactor in the clinical picture of iodine deficiency in Central Africa and could be involved in the aetiology of both forms of cretinism.Clinical TrialControlled Clinical TrialJournal ArticleResearch Support, Non-U.S. Gov'tFLWNAinfo:eu-repo/semantics/publishe