Single and multiple selenium-zinc-iodine deficiencies affect rat thyroid metabolism and ultrastructure

This study was conducted to evaluate the effects of single and combined def iciencies of Se, Zn and I on thyroid function in rats. Rats were fed amino acid-based diets for 6 wk starting from weaning. The diets contained either low or adequate amounts of these minerals. In addition to the control and control pair-fed groups, seven experimental groups were formed: Se deficien t (Se-); I deficient (I-); Zn deficient (Zn-); Se and I deficient (Se-l-); Zn and I deficient (Zn-l-); Se and Zn deficient (Se-Zn); and Se, I and Zn d eficient (Se-l-Zn-). Serum triiodothyronine (T-3) was significantly lower t han in controls in Zn-, Se-Zn- and Se-l- groups. Serum total thyroxine (T-4 ) and free T-4 were significantly lower and thyroid-stimulating hormone (TS H) greater in ail iodine-deficient groups, regardless of Se or Zn status. T hyroid glutathione peroxidase activity was significantly reduced in Se- and Se-Zn- groups. Nevertheless, in the groups with a concurrent I deficiency, the activity of this enzyme was significantly greater than in controls. Se vere alterations of the follicle cellular architecture, including signs com patible with apoptosis, were observed in the Zn- and Se-Zn- groups. These a lterations appeared to be less severe when iodine deficiency was simultaneo usly present. Single and multiple deficiencies of Se, Zn and I have distinc t effects on thyroid metabolism and structure.