Effects of oral therapy with calcium and vitamin D in primary osteoporosis

Eighteen patients (17 women and 1 man) with primary osteoporosis were divided into two groups of 9 patients each. Group A received 2.0 to 2.5 g of calcium and 400 units of vitamin D per day orally and was studied before and after short-term (3 to 4 months) treatment; group B received 1.5 to 2.0 g of calcium per day and 50,000 units of vitamin D twice weekly and was studied before, after short-term, and after long-term (1 year) treatment. In group A there was a decrease (P is less than 0.01) in bone-resorbing surfaces (microradiography of bone biopsy samples) after short-term treatment. In group B there was a decrease (P is less than 0.01) in bone-forming and bone-resorbing surfaces after both short-tern and long-term treatment. Fasting-state (morning) serum immunoreactive parathyroid hormone (iPTH) concentrations decreased after short-term treatment (combined data of groups A and B) and after long-term treatment (group B). We conclude that the principal effect of the oral calcium and vitamin D therapy in primary osteoporosis is to decrease bone turnover. The most probable mechanism for this effect on bone is a partial inhibition of PTH secretion.