Is 1 mg of estradiol valerate or 0.625 mg of conjugated estrogens sufficient for all women to prevent menopausal bone loss?

Bone mineral content was measured by dual photon absorptiometry in 35 women who needed estrogen replacement therapy but did not want the addition of progestogens because they did not want regular bleeding. A total of 23 women were treated with estradiol valerate 1 mg per day over a mean period of 3.7 years; 12 women received conjugated estrogens 0.625 mg per day over a mean period of 5.3 years. The mean values of bone mineral content in both groups did not change. In the women on estradiol valerate, 61% had a decrease, and in those on conjugated estrogens, 67% had a decrease in bone mineral content. However, the calculated decrease per year was within the limits of the intraindividual reproducibility of the measurements. A difference between two measurements with a decrease of > 1.0 g hydroxyapatite/year over a period of > 3 years is larger than the limits of the intraindividual reproducibility. A decrease in bone mineral content > 1.0 g hydroxyapatite/year over a mean period of 3.98 years, SD 0.35, was observed in six of 23 (26%) of the women on estradiol valerate with a mean decrease of 5.28 g hydroxyapatite, SD 0.97. Only one of 12 (8%) of the women on conjugated estrogens had a decrease of 6.1 g hydroxyapatite over a period of 5.2 years. Periodic measurement of bone mineral is recommended in women on estrogen replacement therapy with estradiol valerate 1 mg per day or conjugated estrogens 0.625 mg per day for prevention of postmenopausal bone loss.