ESR2 and polycystic ovary syndrome: Considering direct and indirect effects of estrogen on follicle development, maturation, and ovulation mediated by ERα and ERβ, polymorphisms of ESR1 and/or ESR2 would be expected to be associated with persistent anovulation in PCOS and an ocean of studies focused on genetic variations in ESR1 and ESR2 with pathological dysfunction of ovulation.