Interacting effects of selected trace and toxic metals on thyroid function.

Interacting effects of blood levels of manganese (Mn), selenium, cadmium (Cd), lead (Pb), and mercury, and serum levels of iron (Fe), zinc (Zn), and copper (Cu) on thyroid function in general US population were evaluated. Data from the National Health and Nutrition Examination Survey for 2011-2012 were used for this evaluation. The variables used to evaluate thyroid function were as follows: thyroid-stimulating hormone, free and total triiodothyronine (FT3, TT3), free and total thyroxine (FT4, TT4), and thyroglobulin (Tg). Levels of FT4 were positively associated with the levels of copper and negatively associated with the levels of Fe for males only. Elevated levels of Mn and Fe were associated with increased levels of FT3 for both males and females. TT4 had a positive association with the levels of Cu and a negative association with the levels of Fe for both males and females.