Changes in bone mineral density, insulin-like growth factor-1 and insulin-like growth factor binding protein-3 in kidney transplant recipients. A longitudinal study.

Background: Osteopenia is a major complication of renal transplantation (RTx). This cross-sectional and longitudinal study was planned to better define long-term bone status and relationship to IGF system components.

Methods: Serial measurements of bone mineral density (BMD) and serum markers were performed in 30 patients prior to RTx and at 6 and 12 months following RTx. Serum concentrations of insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein-3 (IGFBP-3), vitamin D, and intact parathyroid hormone (iPTH) were measured.

Results: Serum creatinine, phosphate, alkaline phosphatase and osteocalcine levels decreased, serum calcium levels increased and serum iPTH levels did not change significantly after transplantation. The mean BMD of the vertebrae was 0.97 +/- 0.22 g/cm(2) at the time of RTx, 0.87 +/- 0.21 g/cm(2) 6 months post-RTx (p < 0.05), and 0.81 +/- 0.21 g/cm(2) 12 months post-RTx (p < 0.05). Femur BMD also declined from 0.79 +/- 0.16 to 0.72 +/- 14 g/cm(2) at 12 months (p < 0.05). There was a significant increase in the IGF-1 and a significant reduction in the IGFBP-3 concentrations at 6 months post-RTx (p < 0.05). Significant correlations between serum IGF-1 concentrations and vitamin D concentrations were noted only at 6 months. There was no significant correlation between the BMD and serum IGF system.

Conclusions: These results demonstrate a significant loss of BMD after RTx. The circulating levels of IGF-1 and IGFBP-3 stimulated by the reduction in BMD and IGF-1 secretion are increased in order to restore bone formation.