Thyroid stimulating hormone and selenium supply interact to regulate selenoenzyme gene expression in thyroid cells (FRTL-5) in culture.

In the absence of a sodium selenite supplement, FRTL-5 cells showed a reduced activity of cytosolic glutathione peroxidase (cGSH-Px), a marker of selenium status, indicating the cells were Se-deficient. Se-deficient cells showed a 65% reduction in cGSH-Px mRNA abundance but little change in abundance of either phospholipid hydroperoxide glutathione peroxidase or type 1 deiodinase (IDI) mRNA. In Se-replete cells increased thyroid stimulating hormone (TSH) caused a small decrease in IDI abundance but in Se-deficient cells TSH caused a large increase. The results indicate an interaction between TSH and Se status in the regulation of thyroid selenoenzyme synthesis.