Single and Multiple Selenium-Zinc-Iodine Deficiencies Affect Rat Thyroid Metabolism and Ultrastructure

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Abstract
This study was conducted to evaluate the effects of single and combined deficiencies 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 deficient (Se−); I deficient (I−); Zn deficient (Zn−); Se and I deficient (Se−I−); Zn and I deficient (Zn−I−); Se and Zn deficient (Se−Zn); and Se, I and Zn deficient (Se−I−Zn−). Serum triiodothyronine (T3) was significantly lower than in controls in Zn−, Se−Zn− and Se−I− groups. Serum total thyroxine (T4) and free T4 were significantly lower and thyroid-stimulating hormone (TSH) greater in all iodine-deficient groups, regardless of Se or Zn status. Thyroid 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. Severe alterations of the follicle cellular architecture, including signs compatible with apoptosis, were observed in the Zn− and Se−Zn− groups. These alterations appeared to be less severe when iodine deficiency was simultaneously present. Single and multiple deficiencies of Se, Zn and I have distinct effects on thyroid metabolism and structure.