Differential effects of estrogen treatment on bone mineral density of the spine,hip, wrist and total body in late postmenopausal women

It is commonly believed that estrogen is effective only in preventing menopause-related loss of bone mineral. However, recent studies found significant increases in bone mineral density (BMD) of the spine in response to estrogen, particularly in older women. The degree to which estrogen can restore BMD of the hip is uncertain. In the present study, changes in BMD of the lumber spine (L2–4), hip (neck, trochanter and Ward's triangle), wrist (ultradistal) and total body in response to 1 year of hormone replacement therapy (HRT) were evaluated by dual-energy X-ray absorptiometry (DXA) in women 10 or more years past menopause. Twelve women, aged 61–74 years, received conjugated estrogens 0.625 mg and cyclic medroxyprogesterone acetate 5 mg; 12 women who did not receive HRT were controls. Calcium intake was adjusted to approximately 1500 mg/day in all subjects. There were no differences between the groups in BMD prior to treatment. Increases in BMD of the lumbar spine (mean±SD, 0.041±0.030 g/cm²), hip (neck, 0.019±0.018 g/cm²; trochanter, 0.017±0.012 g/cm²; Ward's triangle, 0.026±0.029 g/cm²) and total body (0.013±0.016 g/cm²) occurred in response to HRT, and these changes were significantly different from those in controls (spine, 0.005±0.020 g/cm²; neck, –0.007±0.026 g/cm²; trochanter, 0.002±0.014 g/cm²; Ward's triangle, 0.003±0.019 g/cm²; total body, –0.001±0.017 g/cm²). HRT appears to be most effective at weight-bearing sites that have a high cancellous bone content. This study demonstrates that HRT significantly increases bone mass of the lumbar spine and proximal femur in osteopenic, late postmenopausal women, and may, therefore, be effective in preventing osteoporotic fractures at these sites in this population.