Altered thyroid hormone production induced by long-term exposure to low doses of the endocrine disruptor dichlorodiphenyltrichloroethane

Endocrine disruptors are exogenous substances that enter the body and exhibit hormone-like action thus disrupting the homeostatic action of endogenous hormones. The most wide-spread disruptor is dichlorodiphenyltrichloroethane (DDT). The aim of this study was to investigate changes in thyroid hormone production induced by prolonged exposure to low doses of DDT. The experiment was performed on male Wistar rats treated with daily doses of DDT 1.89 ± 0.86 μg/kg and 7.77 ± 0.17 μg/kg for six and ten weeks. After six weeks there was a dose dependent increase of serum total thyroxine, total triiodthyronine, and thyroid peroxidase. Subsequently, concentration of free thyroxine decreased. These data indicate that impaired production of thyroxine by follicular thyrocytes, rather than decreased deiodinase activity and blood transport proteins is the major cause of altered thyroid status induced by DDT.