Hormone therapy (HT) can be used to manage problems associated with the decline in ovarian estrogen production after menopause. Menopause occurs naturally when the ovarian follicular pool is functionally exhausted or can be induced by surgical removal of both ovaries. The resulting hypoestrogenic state may adversely affect estrogen target tissues, which include the brain, skeleton, and skin, as well as the cardiovascular and genitourinary systems. The concentration and function of hormone receptors varies in these organs and systems. Differences in genetics, body mass index, and body habitus also may influence the levels of endogenous estrogen and androgen in postmenopausal women. The frequency and severity of menopausal symptoms, the reaction of target tissues to estrogen deficiency, and the response to HT varies significantly among women.