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Last Edited: 1/22/2008

Endocrine Disruptors

Endocrine disruptors (EDs) are chemicals that may act on the endocrine, or hormone, system. They often are similar in structure to natural hormones, so they may mimic or block the actions of the body’s hormones. They may also be called environmental estrogens (although other hormones may be involved) or “hormonally-active agents” (HAAs). The endocrine system regulates numerous functions in our bodies, with hormones acting as messengers between brain and other organs. The endocrine system of primary concern in relation to these chemicals is the one that controls reproduction, including menstrual cycling, sperm production, and normal pregnancy, involving hormones from the brain, pituitary and reproductive organs. Other systems include the thyroid system, which is critical to brain development during pregnancy, and the system that controls glucose (or sugar) levels in our bodies. More and more chemicals that are commonly used have been identified as potentially having these hormonal properties, primarily from animal studies and observations in exposed wildlife. The exposures may be linked to impaired reproduction or infertility, feminization of certain male species, lower sperm counts, delayed or early puberty, and certain cancers, including breast or other reproductive tract cancers. Some of the classes of chemical shown or suspected to have these effects include chemicals found in plastics or household products like phthlates or phenols, fire retardants called poly-brominated biphenyls (PBDEs) or poly-chlorinated biphenyls (PCBs, now banned), pesticides like DDT and others, and heavy metals, like mercury. Some of these chemicals persist in the environment a long time and get into the diet. EHIB staff are conducting a number of projects on these chemicals examining associations with breast cancer, autism, and puberty. In addition, work has been conducted to determine how we are exposed to these chemicals, including measuring levels in the body, also called biomonitoring.

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