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 μg/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 D3 and calcium carbonate did not significantly improve bone loss in long-term renal transplant recipi