Influence of Zinc Deficiency and Effects of Zinc Replenishment on the Thyroid Hormone of Rats Model

Objective The influence of zinc deficiency and effects of zinc replenishment on thyroid hormone of rats were studied. Methods SD rats were randomized into zinc-deficient diet (ZD) group, pair-fed (PF) group, zinc normal group(ZN), zinc supplemented (ZS) group and high zinc (HZ) group. ZD, ZN, HZ were fed with zinc deficient diet ( zinc1 mg/kg), zinc-normal diet (50 mg/kg) and high zinc diet (150 mg/kg) for 8 weeks. ZS group were fed with zinc deficient diet for 3 weeks, and then turned to high-zinc diet for 5 weeks. PF group were fed with zinc normal diet according to the actual quantity of ZD group at the former day. All the animals were sacrificed at the end of the 8-week experiments, and the serum concentration of Zn were measured with polarography, serum concentration of FT_3 and FT_4 measured by radioimmunoassay. Results The serum concentration of Zn decreased significantly owing to zinc deficiency, while serum FT_3 content decreased because of zinc deficiency as well, and restored to normal after zinc was supplemented; when serum levels of FT_4 was not affected. Conclusions Zinc deficiency depresses the thyroid hormone, but FT_4 is not affected.