Ovarian Toxicity of Environmental Toxicants

Ovarian production of oocytes and steroids is choreographed by hypothalamic-pituitary hormones and locally via ovarian derived growth factors and hormones. Environmental chemicals are known to mimic the actions of gonadal steroids such as estradiol or antagonize hormone actions at target tissues. The presence of environmental contaminants in ovarian follicular fluid has been documented and thus has implications for ovarian function and cancer. However, understanding of the risks to ovarian regulation resulting from exposure to environmental contaminants is limited. Therefore a systematic review of the published literature was conducted to characterize the current state of knowledge concerning the ovarian toxicity of environmental toxicants. Herein we argue that the epidemiological literature provides only weak support in favour of the involvement of environmental toxicants in adverse effects on ovarian function. By comparison animal experiments provide evidence of the biological plausibility for environmental toxicants to adversely affect ovarian physiology. Unlike environmental toxicants a strong association has been established linking cigarette smoking and ovarian toxicity. While previous in vitro studies were limited to examining the effects of test compounds on ovarian steroidogenesis, innovative culture methods are opening the door for investigation of time- and stage-dependent effects of toxicants on folliculogenesis. Although evidence of ovarian toxicity in the human population is scant, we propose that inherent limitations of the epidemiological studies together with evidence of biological plausibility provided by animal studies supports the need for further studies to better characterize the mechanism(s) of toxicant action on the ovary.