Effect of 1,25-dihydroxyvitamin D3 and calcium carbonate on bone loss associated with long-term renal transplantation

To investigate the effect of calcitriol plus calcium carbonate on the bone loss associated with long-term renal transplantation, 30 patients with serum creatinine levels less than 2.0 mg/dL were randomly allocated to a control (n = 14) or treatment group (n = 16) and studied with bone biopsy and densitometry at baseline and after 1 year of follow-up. Calcitriol (0.25 mu g/d) plus calcium carbonate (500 mg/d of elemental calcium) were administered to patients in the treatment group, Comparing the baseline and final data of each group at a time, no change in bone mineral density (BMD) z score was observed at the distal radius (control, -0.8 +/- 0.8 versus -0.6 +/- 0.9; treatment, -1.0 +/- 1.0 versus -1.0 +/- 1.1). However, a significant increase (P < 0.05) was found at the lumbar spine in both groups (control, 0.1 +/- 1.6 versus 0.4 +/- 1.6; treatment, -0.1 +/- 1.5 versus 0.3 +/- 1.5) and only in the treatment group at the femoral neck (control, -0.9 +/- 1.0 versus -0.8 +/- 1.0; treatment, -0.5 +/- 0.9 versus -0.3 +/- 1.1). When BMD was compared between groups, no significant differences were observed at the evaluated anatomic sites at baseline or after 1 year of follow-up. After 1 year of follow-up, adjusting for age and sex (z score), the control group showed a trend to reduce the value of several histomorphometric parameters, including osteoblast surface (-2.2 +/- 6.1 versus -3.4 +/- 3.9), osteoid surface (-2.3 +/- 3.5 versus -3.1 +/- 3.9), and osteoclast surface (0.2 +/- 5.0 versus -1.3 +/- 3.3). Consequently, there was a significant reduction (P < 0.05) in mineralizing surface (-9.8 +/- 11.0 versus -15.8 +/- 12.3) and appositional rate (-5.8 +/- 2.7 versus -7.6 +/- 2.2). In the treatment group, a significant reduction (P < 0.05) in osteoclast surface was observed at the end of the study (3.9 +/- 6.8 versus -1.2 +/- 4.1), and although a trend to reduce osteoblast surface (-2.5 +/- 2.6 versus -3.2 +/- 5.7) and osteoid surface (-2.1 +/- 2.5 versus -3.2 +/- 2.8) was also found, patients maintained approximately the same level of wall thickness (-5.2 +/- 5.3 versus -5.3 +/- 3.3) and bone volume (-2.7 +/- 1.8 versus -2.5 +/- 1.7). However, there was no improvement in mineralizing surface (-4.2 +/- 2.9 versus -10.4 +/- 3.6) or appositional rate (-5.8 +/- 3.1 versus -8.1 +/- 2.6). No significant differences in bone histomorphometric variables were observed between groups after 1 year of follow-up. In conclusion, 1,25-dihydroxyvitamin D-3 and calcium carbonate did not significantly improve bone loss in long-term renal transplant recipients. However, significant osteoclast suppression and a trend to maintain trabecular bone volume and wall thickness as well as improve the axial BMD were observed in the treatment group. (C) 2000 by the National Kidney Foundation, Inc.