Treatment of hemodialysis bone disease with 24,25-(OH)2D3 and 1,25-(OH)2D3 alone or in combination

We studied the effects of vitamin D metabolites in 29 patients established on chronic hemodialysis. The patients were divided into four groups; one was treated with 1,25-dihydroxyvitamin D₃ [1,25-(OH)₂D₃] 0.5 μg/day, one with 24R,25-dihydroxyvitamin D₃ [24,25-(OH)₂D₃] 10 μg/day, and one with both metabolites. The control group was not given vitamin D. Plasma levels of both metabolites were low before treatment. 1,25-(OH)₂D₃ levels became normal, and 24,25-(OH)₂D₃ increased to supranormal levels after administration of the corresponding metabolite. Combined treatment produced still higher plasma levels of 24,25-(OH)₂D₃, suggesting an interaction between the two metabolites. Patients receiving 1,25-(OH)₂D₃ alone had a greater increase in plasma calcium than those receiving both metabolites. In control patients, hyperparathyroid bone disease worsened over the 10-month observation period. 1,25-(OH)₂D₃ improved hyperparathyroid bone disease in most patients, as reflected by a reduction in osteoclast and osteoblast numbers, but had no demonstrable effect on mild osteomalacia. 24,25-(OH)₂D₃ had no significant effect on plasma biochemistry or bone histology, and the effect of combined treatment on histology was similar to that of 1,25-(OH)₂D₃ alone. Stainable bone aluminum increased slightly in patients given 1,25-(OH)₂D₃, but aluminum did not affect the response to treatment. We conclude that 1,25-(OH)₂D₃ is a useful agent in the treatment of renal bone disease, but no therapeutic role is apparent for 24,25-(OH)₂D₃.