This kit is used for quantitative determination of estradiol (E2) in human serum in vitro. Estradiol (E2) in female mainly comes from follicle, corpus luteum and placenta, and in male mainly comes from testis. After pregnancy, dehydroepiandrosterone (DHA) in maternal and fetal blood is converted into E2 and E1 (40:60) in placenta. Estradiol (E2) is a kind of sterol hormone, which is mainly released into the blood by the secretion of ovary, placenta or testis. E2 is the most biologically active estrogen. The level of E2 in the blood changes with the change of menstrual cycle.