Environmental Thyroid Disruptors and Human Endocrine Health

In the last 30 years, there is increasing concern about chemical pollutants that have the ability to act as hormone mimics. Because of structural similarity with endogenous hormones, their ability to interact with hormone transport proteins, or their ability to disrupt hormone metabolism, these environmental chemicals have the potential mimic, or in some cases block, the effects of endogenous hormones (Safe, 2000). In either case, these chemicals serve to disrupt the normal actions of endogenous hormones and thus have become known as “endocrine disruptors”. An endocrine disruptor is defined as “an exogenous agent which interferes with the synthesis, secretion, transport, binding, action or elimination of natural hormones in the body which are responsible for maintenance of homeostasis, reproduction, development or behavior” (Massart et al., 2006a). This wide definition includes all substances that can affect endocrine function via interference with estrogen, androgen or thyroid hormone (TH) signaling pathways.