March, 2003 -- Indian researchers conducted animal studies that gave the antithyroid drug methimazole, alone, and along with antioxidants, including vitamin C, vitamin E and turmeric extract (TE).

At the conclusion of the experiments, thyroid weights, thyroxine (T4), triiodothyronine (T3) and cholesterol levels were evaluated. Those animals receiving methimazole had increased thyroid weight, very low levels of circulating T4 and T3, and elevated levels of cholesterol. Those animals who received Vitamins C, E or turmeric extract along with methimazole showed reduced weights (38-55% less) in thyroid glands (P < 0.01), less suppressed T4 and T3 levels (2-6% and 7-35% respectively) and less increase in total cholesterol levels (19-52%).

The data suggested that antioxidants could be having a direct, positive effect on the thyroid gland.

Source: Deshpande UR, et. Al. "Effect of antioxidants (vitamin C, E and turmeric extract) on methimazole induced hypothyroidism in rats," Indian J Exp Biol 2002 Jun;40(6):735-8