Last update:
01-Feb-2012

Endocrine disruptors are chemical substances (natural or synthetic) that interfere with endogenous hormone function in humans and animals. The use of these chemicals is widespread and the sources of human exposure are multiple, including food, water, air and soil. Maternal-child exposure (through the placenta or breast milk) is an additional source. More than one hundred natural or synthetic compounds affecting thyroid function by multiple mechanisms have been identified. Endocrine disruptors may inhibit thyroidal iodine uptake (perchlorate, thiocyanate and nitrate ions), or thyroperoxidase activity (isoflavones), act directly on the thyroid hormone receptor (polychlorinated biphenyls, polybrominated biphenyls, bisphenol-A and triclosan), or affect the transport and metabolism of thyroid hormones (polychlorinated biphenyls, polybrominated biphenyls, genistein, dioxins and others). Exposure to endocrine disruptors is an important health issue for the general population, but humans are more vulnerable during gestation and childhood, as endocrine disruptors may affect development at several stages. In certain cases there is a significant time lag between exposure to endocrine disruptors and clinical presentation of the effects, which makes their study particularly difficult. Some thyroid disruptors have been studied exclusively in vitro or in experimental animals, and their effects in humans are still under investigation. In this review, thyroid disruptors are classified and presented according to their mode of action, including their potential role in thyroid tumorigenesis. Additional epidemiological studies are needed to further elucidate their action. Preventive strategies are becoming necessary to avoid public exposure to these substances.

Key words: Endocrine disruptors, Metabolism, Thyroid, Thyroid cancer, Thyroid hormone.