17-estradiol (E2) and the related steroidal hormones play an important role in multiple physiological processes. However, these hormones are risk factors for hormone-dependent diseases including breast and endometrial cancer. Inappropriate exposures (high or low) to estrogens can also lead to adverse health effects. The identification of estrogenic compounds in the environment, coupled with human exposures to these compounds, has generated public, regulatory, and scientific concern regarding their potential hormonal toxicity to humans and wildlife. This chapter focuses on chemical-induced estrogenicity and the potential toxicological impacts of these compounds. It also describes several different structural classes of synthetic estrogenic compounds, phytoestrogens, and estrogens/antiestrogens such as diethylstilbestrol and tamoxifen that are used as pharmaceutical agents. In addition, the mechanism of estrogen action and implications for risk assessment of these compounds are also discussed. These factors highlight the challenges faced by scientists and regulators in addressing the health risks and benefits of estrogenic compounds. 2007 Elsevier Ltd. All rights reserved.
