Does 24R,25(OH)2-vitamin D3 prevent postmenopausal bone loss?

Summary The effect of oral 24R,25(OH)₂-vitamin D₃ as a prophylactic for postmenopausal bone loss was examined. Fifty-eight healthy, early postmeno-pausal women entered a double blind therapeutic trial for 2 years. After an initial examination the women were randomized to treatment with 10 μg 24R,25(OH)₂D₃ daily or placebo. Participants were thereafter examined every 3 months (nine examinations in all). In both groups the forearm bone mineral (measured by single photon absorptiometry), the lumbar spine mineral, and the total body mineral (measured by dual photon absorptiometry) fell significantly and the same magnitude. Further-more, serum calcium, serum alkaline phosphatase concentration, and fasting urinary hydroxyproline were unchanged, as were the 24-hour urinary calcium excretion and the intestinal radiocalcium absorption. Our findings demonstrate that 24R,25(OH)₂D₃ treatment has no prophylactic effect on postmenopausal bone loss and does not alter calcium metabolic variables.