Treatment with vitamin 24,25 (OH)2D3 does not change serum levels of 1,25 (OH)2D or urinary calcium excretion rate in man.

40 healthy early postmenopausal women participated in a controlled therapeutic trial with the aim of examining whether treatment with 24,25 vitamin D3 changed the serum concentration of either 1,25 (OH)2D and/or the 24-hour urinary calcium excretion rate. The 40 women were randomized to treatment with either 24R,25 (OH)2D3 (10 micrograms daily) or placebo. Serum concentrations of calcium, 25 (OH) D, 1,25 (OH)2D, 24,25 (OH)2D3 and 24-hour urinary calcium excretion rate were measured before (t0) and after (t1) 6 months of treatment. In the 24,25 (OH)2D3 treated group there was a highly significant increase in the mean serum 24,25 (OH)2D3 concentration, whereas serum 25 (OH) D and 1,25 (OH)2D and serum and urinary calcium were unchanged during the trial. In the placebo group all values were similar before and after the trial. We conclude that treatment with 24,25 (OH)2D3 is not an alternative to conventional treatment of renal hypercalciuria.