Heavy Metals Acting as Endocrine Disrupters

Last years researches focused on several natural and synthetic compounds that may interfere with the major functions of the endocrine system and were termed endocrine disrupters. Endocrine disrupters are defined as chemical substances with either agonist or antagonist endocrine effects in human and animals. These effects may be achieved by interferences with the biosynthesis or activity of several endogenous hormones. Recently, it was demonstrated that heavy metals such as cadmium (Cd), arsen (As), mercury (Hg), nickel (Ni), lead (Pb) and zinc (Zn) may exhibit endocrine-disrupting activity in animal experiments. Emerging evidence of the intimate mechanisms of action of these heavy metals is accumulating. It was revealed, for example, that the Zn atom from the Zn fingers of the estrogen receptor can be replaced by several heavy metal molecules such as copper, cobalt, Ni and Cd. By replacing the Zn atom with Ni or copper, binding of the estrogen receptor to the DNA hormone responsive elements in the cell nucleus is prevented. In both males and females, low-level exposure to Cd interferes with the biological effects of steroid hormones in reproductive organs. Arsen has the property to bind to the glucocorticoid receptor thus disturbing glucocorticoids biological effects. With regard to Hg, this may induce alterations in male and female fertility, may affect the function of the hypothalamo-pituitary-thyroid axis or the hypothalamo-pituitary-adrenal axis, and disrupt biosynthesis of steroid hormones.