Combined treatment with calcitonin and 1,25-dihydroxyvitamin D3 for osteoporosis in women.

Twenty-two middle-aged women with severe osteoporosis were treated for 2 years with either 0.5 mg of synthetic human calcitonin subcutaneously three times per week combined with 0.5 micrograms of calcitriol and 0.5 g of calcium per day orally or calcium only. The treatment with calcitonin plus calcitriol (12 patients) resulted in a significantly increased calcium absorption rate. The mean values for serum phosphate did not change during the treatment period and the mean values did not differ between the treatment groups, but the serum calcium and urinary Ca/Cr ratio increased somewhat in the group given the combined treatment. There was no evidence that the combined treatment improved the bone density in this study. It is possible that calcitriol, instead of increasing the effect of calcitonin by suppression of the parathyroid, might have counteracted its effect by increasing the bone resorption.