Unique effects of 24,25-dihydroxyvitamin D3 in uremic patients.

The effects of 24,25-dihydroxyvitamin D3 (24,25[OH]2D3), given orally for 7-10 days at doses of 2 and 4 microgram/day, were evaluated in patients with advanced renal failure. There was a significant fall in serum Ca and a rise in alkaline phosphatase; both returned to pretreatment levels 2 weeks after cessation of therapy. There was no change in intestinal absorption of 47Ca. These observations are significantly different from those observed during treatment with 1,25(OH)2D3 or 25(OH)D3, indicating that different vitamin D sterols can clearly exert different biologic effects.