Estrogen therapy in postmenopausal osteoporosis. What we know and what we don't.

Replacement estrogen therapy is of proven efficacy for the prevention and treatment of postmenopausal bone loss. Oral and transdermal 17 beta estradiol have provided similar benefits in clinical studies. The lowest effective doses are 0.625 mg per day for conjugated estrogens, 2 mg per day for oral 17 beta estradiol, 1.5 micrograms per day for 17 beta estradiol gel, and 50-microgram 17 beta estradiol patch per day. Bone mineral density should be monitored if lower doses are used. Several epidemiologic studies found that a decrease in the incidence of osteoporotic fractures was achieved only when the duration of estrogen replacement therapy exceeded seven years. It follows that replacement therapy should be started at cessation of menses, if possible. However delayed replacement therapy (i.e., at 65 years of age) is unquestionably effective.