Estrogen replacement therapy: an overview.

Levels of circulating estrogen fall during the perimenopausal period, resulting in changes in the postmenopausal woman's genitourinary tract, central nervous and cardiovascular systems, skin, and bone. Exogenous estrogen minimizes the benign symptoms and prevents the increased incidence of osteoporosis and atherosclerotic heart disease that accompany estrogen deficiency. Thus to avoid the recognized problems of estrogen deficiency, nearly all women should begin a lifelong course of estrogen replacement therapy during the perimenopausal period.