Estradiol is a natural byproduct of cholesterol metabolism found widely in nature. During much of a woman’s life, significant amounts of estradiol are produced by the ovaries in order to facilitate the reproductive cycle and maintain fertility. The hormone, which is the most active human female sex hormone, is also largely responsible for the maintenance of secondary female sexual characteristics. In menopausal women, production of estradiol and the other estrogens gradually decreases, disrupting the activity of other hormones in the body and the neurovascular mechanism found in the hypothalamus, sometimes resulting in hot flashes and other adverse effects. Women that suffer from severe menopausal symptoms are sometimes prescribed hormone replacement therapy, which involves the administration of synthetic estrogens.