Ovarian actions of estrogen receptor-β: An update

Estrogen is essential for folliculogenesis with independent roles attributed to each of the two estrogen receptors (ERs). ER, expressed predominantly by the ovarian granulosa cells, is required for antrum formation, preovulatory follicle maturation, expression of genes involved in ovarian differentiation (luteinizing hormone, aromatase, etc.), and follicle rupture during ovulation. Ovulatory dysfunction is associated with polymorphisms of the ER gene, and endocrine disruptors that selectively activate ER cause reproductive dysfunction and impairment fertility. ER may also exhibit antitumorigenic properties, with a decline in ER levels in epithelial ovarian cancers associated with more severe disease and poor prognosis. In this review, we examine the models that have been used to elucidate the roles ER plays in the ovary and consider the clinical consequences of altered ER expression or inappropriate activation of ER signaling.