Abstract
Because of the finding of low calcium absorption and low serum 1,25(OH) sub(2)D levels in osteoporotic patients, the authors decided to initiate a randomized study in an unselected group of previously untreated osteoporotic patients, in which the authors could compare the effects of the administration of synthetic 1,25(OH) sub(2)D sub(3) with that of placebo on metabolic balance, calcium kinetics and bone histology. In order to find out the therapeutic dose of 1,25(OH) sub(2)D sub(3) a double isotope calcium absorption test (10) pre and post seven days of therapy was performed. 50 percent of normal subjects did not increase fractional calcium absorption at a dose of 0.2 mu g daily for seven days. However, all normal subjects and 17/20 osteoporotics significantly increased calcium absorption on a seven day course of 0.4 mu g daily. Reproducibility of the calcium absorption test was carried out in 17 normal subjects and 14 osteoporotics.