What is Estradiol (E2)? Estrogen is the main female sex hormone, and estradiol, also called 17 beta-estradiol, is a form of estrogen. Estradiol (E2) and estrone (E1) are prominent biologically active estrogens in women. A third bioactive estrogen, estriol (E3) is the primary estrogen in pregnancy. Both women and men have estrogen in their bodies. … Continue reading Estradiol (E2)