Clinical Significance

Estradiol is a steroid hormone and E2 is released into the bloodstream from the testes, ovaries and placenta, or from extra-gonadal conversion of androgens; E2 is the most biologically active naturally occurring estrogen. In ovulating women, E2 is initially derived from a group of maturing follicles and eventually from an intact ovulation and the corpus luteum formed from it. In postmenopausal women, E2 is derived from the conversion of androgens, and circulating E2 levels are low and non-cyclical. Prepubertal children and males also have low E2 levels that are not cyclical.