Introduction: Estradiol (E2 or 17beta-estradiol) (also oestradiol) is a sex hormone. During the reproductive years, most estradiol in women is produced by the granulosa cells of the ovaries by the aromatization of androstenedione (produced in the theca folliculi cells) to estrone, followed by conversion of estrone to estradiol by 17beta-hydroxysteroid reductase. Smaller amounts of estradiol are also produced by the adrenal cortex, and (in men), by the testes. Estradiol is not only produced in th