Estrogen is the primary hormone responsible for female characteristics. The three main types of estrogen are estrone(1), estradiol(2), and estriol(3). Estrogen receptor cells are present in the arteries, bladder, bones, brain, heart, liver and vagina. Estradiol is produced mainly by the ovaries and, of the three; it is the most stimulating to the breast tissue. Estriol, (made from both estrone and estradiol) is the main circulating estrogen about 80% in young women and believed to be less stimulating. It is also the predominant estrogen in pregnancy. Estrone is most prevalent after menopause, and is produced by conversion of adrenal DHEA in fat cells, and also from the conversion of estradiol. Estrogens may be helpful in relieving the symptoms menopause, such as hot flashes, vaginal dryness, mood swings, night sweats as well as possibly helping the urinary tract, breasts, skin health, blood vessels, and keeping the uterus flexible and tone. Estrogens may also slow the development of osteoporosis by slowing down the rate of bone loss.