Serves as the primary ‘”reservoir” of estrogen, and
dominant estrogen remaining AFTER menopause
. It is produced primarily in the ovaries, body fat, and breast. E2, Estradiol; Serves as the primarily active estrogen BEFORE menopause and is LOST at menopause when follicles are gone. It is produced primarily in the ovaries with some made from testosterone in the brain, breast, and muscle. E3, Estriol; A weak estrogen made by the placenta during pregnancy.