Estrogen and the prevention and treatment of osteoporosis.

Osteoporosis is a systemic skeletal disease characterized by decreased bone mass and impaired structural integrity of remaining bone. Due to a decline in circulating estrogen, an acceleration of bone loss occurs after the menopause. Osteoclast activity is increased, leading to an imbalance of bone resorption over formation, resulting in a net loss of bone. Estrogen is an effective antiresorptive agent used in both the prevention and treatment of osteoporosis. Estrogen replacement effectively maintains bone mass and prevents fractures. Replacement therapy is most effective when it is initiated soon after the cessation of menses and is continued long term. Historically, there is a low compliance rate with long-term therapy in this country. The addition of a progestin to estrogen replacement is necessary for endometrial protection but negatively affects patient compliance. The identification of other significant medical benefits, such as the reduction of cardiovascular risk and possible amelioration of Alzheimer's dementia, affirm the cost-effectiveness of estrogen replacement and may increase its attractiveness to patients. Clarification of breast cancer risk and improvement of an individual's side effect profile through use of different regimens, hormonal preparations, and routes of administration may enhance compliance.