Treatment of renal osteodystrophy in children with dihydrotachysterol and 24,25-dihydroxyvitamin D3.

The effect of administration of 25 micrograms 24,25-dihydroxyvitamin D3 (24,25(OH)2D) combined with dihydrotachysterol (DHT2) on clinical, radiological, biochemical and bone histological parameters was assessed in ten children on chronic hemodialysis. Eight children had been treated with DHT2 prior to administration of 24,25(OH)2D. Addition of 24,25(OH)2D to the treatment resulted in a decrease in serum calcium values. Therefore higher doses of DHT2 were required to maintain serum-calcium levels between 2.4-2.8 mmol/l. Administration of 24,25(OH)2D did not modify the quality of bone, but histomorphometric investigation did show a significant reduction of the surface percentage of bone trabecula, in the iliac crest, covered with osteoclasts (oc%). Following the administration of 24,25(OH)2D an increase in bone mineralization was shown by X-rays of the wrists and measured by dual photonabsorptiometry. Addition of 24,25(OH)2D to the DHT2 treatment resulted in an increase in serum concentration of 24,25(OH)2D and a decrease in DHT2 levels. The present study suggests that administered 24,25(OH)2D interferes with DHT2 metabolism and increases DHT2 tolerance. Increased bone mineralization may be related to 24,25(OH)2D, a higher dose of DHT2 or both.