Does calcium potentiate the effect of estrogen therapy on postmenopausal bone loss?

Calcium metabolism were examined in 66 healthy postmenopausal women every 3 months during 2 years of treatment with oral or percutaneous 17 beta-estradiol combined with different doses of calcium supplementation. Bone mineral content measured in the forearm (single photon absorptiometry) in the spine and in the total skeleton (dual photon absorptiometry) was unchanged in all estrogen-treated groups during the two years of treatment, and the responses in the groups with and without calcium supplementation were not significantly different. Furthermore, the responses were independent of route of administration of the estrogen. Biochemical indices of bone turnover (serum alkaline phosphatase and fasting urinary hydroxyproline/creatinine) decreased highly significantly during estrogen treatment (P less than 0.001) independent of route of administration of the estrogen and of the calcium supplementation. We conclude that calcium supplementation has no additive effect to estrogen therapy in the prevention of the early postmenopausal bone loss.