The effects of plasma estradiol levels on increases in vertebral and femoral bone density following therapy with estradiol and estradiol with testosterone implants

Abstract

Percutaneous estradiol (E2) implants effectively preserve bone density in postmenopausal women. However, these implants are often given with testosterone, which may itself have an anabolic effect on bone. To determine whether testosterone confers any additional bone-sparing effect, we studied 50 postmenopausal women randomly allocated to receive E2 (75 mg) alone or with testosterone (100 mg) every 6 months for 1 year. Women with an intact uterus received cyclic norethindrone (5 mg) for 10 days of each calendar month. Twenty-five untreated women were recruited to act as a reference group. Bone density was measured at the lumbar spine and proximal femur by dual x-ray densitometry. By 1 year, bone density at the lumbar spine had fallen by 1.8% in the reference group. In the women treated with E2 alone, it increased significantly by 7.8% (P less than .0001) and in those receiving E2 with testosterone, it increased by 6.3% (P less than .0001). At the femoral neck, bone density decreased by 3% in the controls and increased by approximately 4% in both treated groups (P less than .0001). The increase in bone density at these sites was unrelated to the woman's chronological age, menopausal age, or initial bone density. However, it correlated significantly with the serum E2 levels attained after 1 year of therapy. In no treated patients did bone density decrease significantly. These data show that testosterone confers no additional bone-sparing effect in postmenopausal women.