Environmental Endocrinology: Endocrine Disruptors and Endocrinopathies

Abstract

An endocrine disruptor (ED) is defined by the USEnvironmental Protection Agency as “an exogenous agent that interferes with the production, release, transport, metabolism, binding, action, or elimination of natural hormones in the body responsible for the maintenance of homeostasis, reproduction, development, and/or behavior” (U.S. EPA., 1997). This definition encompasses a rather heterogeneous group of molecules from naturally occurring substances (e.g., phytoestrogens) to biochemically manufactured compounds such as plasticizers, pesticides, industrial solvents, pharmaceutical agents (diethylstilbestrol) and heavy metals. Endocrine disruptors were originally considered to exert their biological action through nuclear steroid receptors by mimicking or antagonizing natural hormone’s action (Waring & Harris, 2005) with the majority of them acting as pseudoestrogens and less possessing antiandrogenic or anti-estrogenic properties ( McLachlan et al., 2006 ). Today, basic scientific research shows that the mechanisms are much broader than originally recognized and include interaction with transcriptional factors, non-nuclear steroid hormone receptors, gene regulation or even transgenerational effects by targeting germ cell lines (Anway & Skinner, 2006, 2008; Tabb & Blumberg, 2006). In addition, targets for endocrine disruption extend beyond the traditional estrogen/androgen -mediated reproductive system. Within the last few years, scientists also have expressed concern about the potential role of EDs in increasing trends in obesity and diabetes, the major life-threatening diseases of modern word. At present, all hormonesensitive physiological systems seem to be vulnerable to EDs, including brain and hypothalamic neuroendocrine systems; pituitary; thyroid; cardiovascular system; mammary gland; adipose tissue; pancreas; ovary and uterus in females; and testes and prostate in males (Diamanti-Kandarakis et al., 2009). Undoubtedly, the issue of endocrine disruption has attracted considerable scientific attention with the weight of data obtained from wildlife populations, animal models and epidemiological studies growing extensively during the last years. After all, the unprecedented increase in the production and use of industrial and agricultural chemicals during last decades makes human exposure inevitable through multiple sources. Adults are exposed mainly through the ingestion of contaminated drinking water, food and breathing polluted air. Infants are exposed to EDs through breast milk, baby products, and polluted