Human exposure to medicinal, dietary, and environmental estrogens

Estrogens are a broad class of compounds which exert many physiological effects. In addition to gonadal and peripheral endogenous estrogen production, humans can be exposed to exogenous estrogenic compounds (xenoestrogens) from medicinal, dietary and environmental sources. These compounds can exert effects similar to that of 17 -estradiol (E2) through estrogen receptor (ER)-mediated mechanisms, or via ER-independent pathways. Although estrogens are used for a number of medical purposes such as birth control and for hormone replacement therapy (HRT) in the treatment of post-menopausal symptoms, studies have found adverse health effects from their use. Increased risk of stroke and invasive breast cancer are associated with medicinal estrogen use. As an alternative to HRT, diets rich in phytoestrogens are used by many women. Even though phytoestrogen consumption is associated with reduced risk of hormone-dependent cancers and antioxidant properties, concerns about adverse effects, such as endocrine disruption, cannot be dismissed. Widespread use of chemicals with estrogenic properties in agriculture and industry has resulted in endocrine disruption in wildlife populations although the impact on human health is still in debate. In general, the ranking order of estrogen equivalent factors compared to E2 is medicinal estrogens > phytoestrogens > environmental estrogens. Serum concentrations of estrogens vary among populations depending on choice of diet, use of medicinal estrogens, and environmental exposure. Thus, determination of total exposure levels (i.e. E2 equivalent concentration) is complex and can vary greatly within a larger population.