Assessment of combined 24,25(oh)₂d₃ and 1α(oh)d₃ therapy for bone disease in dialysis patients

An increasing body of experimental data suggests a role for 24,25(OH)₂D₃ in bone metabolism. The present study was carried out to assess a possible therapeutic role of this vitamin D metabolite in renal osteodystrophy. Twenty-two chronic dialysis patients, most of whom were previously maintained on 1α(OH)D₃ therapy, received additional treatment with 10 μg/day 24,25(OH)₂D₃ and were compared to 19 patients receiving 1α(OH)D₃ alone. Analysis of transiliac bone biopsies obtained at study entry and following 10-16 months of treatment revealed that the combined therapy produced a decrease in bone turnover. Specifically, the addition of 24,25(OH)₂D₃ inhibited an increase in trabecular bone volume ( BV TV) and suppressed osteoclastic parameters. Thus BV TV increased from 26.2 ± 8.6 to 32.1 ± 7.5% (p < 0.01) in the 1α(OH)D₃ group, but it remained unchanged in the combined therapy group. In contrast, the eroded surface ( ES BS), the osteoclast surface ( Oc.S BS), and the osteoclast numbers were significantly suppressed in patients receiving both 24,25(OH)₂D₃ and 1α(OH)D₃, as compared with those receiving 1α(OH)D₃ alone (p < 0.01, p < 0.01, and p < 0.001, respectively). These improvements were independent of changes in 1α(OH)D₃ dosage. The extent of bone aluminium deposits was unrelated to the administration of 24,25-(OH)₂D₃ or to its effect. 24,25(OH)₂D₃ therapy was not associated with any adverse effects.