Effect of cadmium on thyroid function in sheep

摘要

The objective of this experiment was to determine the effect of long-term low-dose administration of cadmium on thyroid function in sheep. In this experiment, ten healthy Iranian male sheep, aged about 1 year old, were randomly allocated into two equal groups of control (n = 5) and experiment (n = 5). Both groups were kept under the same conditions of food and environment. Treatment group received cadmium chloride (1 mg/kg/day) orally for 8 weeks. Blood sampling of two groups was done on days 0, 14, 28, 42, 56, and 70 every morning (8 to 9 a.m.). The function of the thyroid was evaluated by measuring the levels of serum thyroid hormones T3, T4, FT3, FT4, and TSH. The hepatic function in both groups was evaluated by measuring hepatic enzyme activities including alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ glutamyl transferase (GGT), and total bilirubin (TBIL). Serum levels of T3, T4, FT3, FT4, and TSH significantly decreased in cadmium-treated sheep when compared to control group (p < 0.05). Serum enzyme activities of ALT, AST, GGT, and TBIL in Cd-treated sheep were significantly increased in comparison with control group (p < 0.05). Our findings suggest that Cd-exposed sheep can be at a risk of low thyroid function.