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The three naturally occurring estrogens are estradiol, estriol and estrone. In the body these are all produced from androgens through enzyme action. Estradiol is produced from testosterone and estrone from androstenedione. Estrone is weaker than estradiol, and in post-menopausal women more estrone is present than estradiol.
While estrogens are present in both men and women, it is found in women in significantly higher quantities. They promote the development of female secondary sexual characteristics, such as breasts, and are also involved in controlling the menstrual cycleThe menstrual cycle is the periodic change in a woman's body that occurs every month between puberty and menopause and is related to reproduction. The average human menstrual cycle is 28 days long, but it can range from 21 to 35 days. It is controlled by, which is why most birth control pills contain estrogens.
The use of estrogen, especially together with progesteroneProgesterone is a steroid hormone involved in the female menstrual cycle, pregnancy (supports gestation and embryogenesis of humans and other species. Progesterone levels vary during the menstrual cycle and it is an ingredient of most birth control pills, is a controversial treatment for the symptoms of menopause which may do as much harm as good.