Fibroblast Growth Factor-23 and Parathyroid Hormone Are Associated with Post-Transplant Bone Mineral Density Loss

Background and objectives: Among the multiple factors contributing to bone mineral density (BMD) loss after renal transplantation, hypophosphatemia is increasingly recognized to play an important role. Hypophosphatemia occurs in up to 90% of the renal transplant recipients in the early post-transplant period and is caused by renal phosphate wasting. We hypothesized that a high pretransplant level of the recently described phosphaturic hormone fibroblast growth factor 23 (FGF-23) is a risk factor for accelerated BMD loss occurring within the first post-transplant year. Design, setting, participants, & measurements: We performed a two-center observational retrospective cohort study in 127 incident renal transplant recipients. Serum full-length FGF-23, parathyroid hormone (PTH), and parameters of mineral metabolism were determined at the time of transplantation. BMD was assessed by osteodensitometry at the time of transplantation and 1 year later. Results: A moderate decrease of BMD was observed during the first post-transplant year. High FGF-23 levels were associated with BMD loss at the lumbar spine and total hip region, whereas low PTH levels were associated with BMD loss at all three regions. Cumulative doses of prednisone and post-transplant serum phosphate level were not correlated with BMD changes. Conclusion: Our data indicate that patients with a high serum FGF-23 level and/or a low PTH level at the time of transplantation are at risk for increased BMD loss during the first post-transplant year. Clin J Am Soc Nephrol 5: 1887-1892, 2010. doi: 10.2215/CJN.00950110