Early postmenopausal bone loss is prevented by estrogen and partially by 1alpha-OH-vitamin D3: therapeutic effects of estrogen and/or 1alpha-OH-vitamin D3.

A total of 79 Japanese women who were within 5 years of menopause were randomly assigned 1alpha-hydroxyvitamin D3 [1alpha(OH)D3] 1.0 microg/day, conjugated estrogens 0.625 mg/day, a combination of both, or control (no treatment). Lumbar spine and proximal femur bone mineral density (BMD) and biochemical indices were monitored over 2 years. In the 1alpha(OH)D3-treated group, there was a nonsignificant decrease in lumbar spine BMD compared with controls, and no significant loss in the femoral neck compared with controls. In the estrogen-treated group, there was a nonsignificant increase in spine BMD (+2.17% in the first year and +1.71% in the second year), and no loss in femoral neck BMD. The combination of conjugated estrogens +1alpha(OH)D3 was more effective in increasing BMD in the spine (+3. 68% in the first year and +3.63% in the second year) and femur (+2. 56% in the first year and +4.44% in the second year) BMD. There was a significant difference in lumbar spine BMD in both the first and second years between the combination-treated group and the 1alpha(OH)D3-treated and control groups (P < 0.01). Serum osteocalcin (OC) significantly decreased in the combination-treated group (-23.8% in the first year) and the estrogen-treated group (-37. 6% and -41.2% at 6 and 18 months, respectively), and serum alkaline phosphatase (Alp) decreased significantly in the first year in the combination-treated (-31.5%), estrogen-treated (-27.3%), and 1alpha(OH)D3-treated (-7.9%) groups, whereas serum OC increased (+45. 4% in the first year) in women without treatment. The results of this study indicate that early postmenopausal bone loss in the femoral neck is prevented by conjugated estrogens, 1alpha(OH)D3, or both, whereas bone loss in the spine is not prevented by 1alpha(OH)D3. Estrogen proves effective in preventing early postmenopausal bone loss by markedly inhibiting bone turnover. Moreover, a synergistic bone-sparing effect can be expected when estrogen is administered concomitantly with 1alpha(OH)D3 rather than when used alone.