ASSOCIATIONS BETWEEN LOW-LEVELS OF SERUM ESTRADIOL, BONE-DENSITY, ANDFRACTURES AMONG ELDERLY WOMEN - THE STUDY OF OSTEOPOROTIC FRACTURES

To evaluate the skeletal effects of endogenous serum estradiol, we mea sured bone mineral density (BMD) at the calcaneus and radius (single p hoton absorptiometry) and at the hip and spine (dual x-ray absorptiome try) in 274 women aged 65 yr or more who participated in the Study of Osteoporotic Fractures. Lateral radiographs of the thoracic and lumbar spine were also taken, and serum was assayed for estradiol. Those who had estradiol levels from 10-25 pg/mL had 4.9%, 9.6%, 7.3%, and 6.8% greater BMD at total hip, calcaneus, proximal radius, and spine than t hose with levels below 5 pg/mL. After multiple adjustments, BMD differ ences remained statistically significant and corresponded to about 0.4 so. Vertebral deformities were less prevalent among women whose estra diol level exceeded 5 pg/mL; the multiple adjusted odds ratio was 0.4 (95% confidence interval, 0.2-0.8). We conclude that physiologically l ow estradiol has a salutary effect on the skeleton in elderly women, p ossibly by reducing skeletal remodeling.