effect of mercury on thyroid function in sheep

The purpose of this experiment was to determine the effect of long-term low-dose administration of mercury [Hg] on thyroid function in sheep. In this experiment, 10 clinically healthy, adult, male Iranian sheep, aged approximately 1 year, were randomly allocated into the control [n=5] and mercury [Hg-]-treated [n=5] groups. Both groups were kept under identical conditions in terms of food and environment. The treatment group received mercuric chloride [5 mg/kg/day] orally for eight weeks. Blood samples were drawn between the hours of 0800 and 0900 from both groups on days 0, 14, 28, 42, 56 and 70. Thyroid function was evaluated by measuring the levels of the serum thyroid hormones, including triiodothyronine [T3], thyroxine [T4], free T3 [FT3], free T4 [FT4] and thyroid-stimulating hormone [TSH]. Hepatic function was evaluated in both groups by measuring alanine aminotransferase [ALT], aspartate aminotransferase [AST], gamma-glutamyltransferase [GGT] and total bilirubin [TBIL]. Renal function was assessed using serum creatinine [Cr] and blood urea nitrogen [BUN] levels. Serum T3 [from day 28 onwards] and serum T4, FT3, FT4 and TSH [from day 14 onwards] decreased in the Hg-treated group [p<0.05]. Serum ALT, AST and GGT increased from days 42, 56 and 70, respectively, when compared to the control group [p<0.05]. The concentrations of total protein and albumin decreased on day 70 and total bilirubin [TBIL], BUN and Cr levels increased on day 70 when compared to the control group [p<0.05]. It was concluded that chronic administration of Hg may expose sheep to the risk of hypothyroidism

Effect of lead on thyroid function in sheep

The objective of this experiment was to determine the effect of long-term low-dose administration of lead [Pb] on thyroid function in sheep. In this experiment 10 healthy Iranian male sheep, aged about one-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. The treatment group received lead acetate [5 mg/kg/day] orally for 8 weeks. Blood sampling of two groups was done on the same days, on days 0 [before receiving lead acetate in treatment group], 14, 28, 42, 56 and 70 after lead administration, 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 alanin amino transferase [ALT], aspartate aminotreansferase [AST], gamma glutamyl transferase [GGT], and total bilirubin [TBIL]. Serum levels of T3 [on days 14, 56 and 70] T4 [on days 14, 28, 42, 56 and 70], FT3 [on days 56 and 70], FT4 [on days 42, 56 and 70] and TSH [on days 14, 28, 42, 56 and 70] significantly decreased in lead-treated sheep when compared to the control group [P<0.05]. Serum enzyme activities of ALT [on days 28 and 42], AST [on days 28, 42, 56 and 70] and TBIL [on days 28 and 70] in Pb treated sheep increased significantly in comparison with the control group [P<0.05]. Our findings suggest that Pb exposed sheep can be at risk of low thyroid function