Earlier Decrease of FGF-23 and Less Hypophosphatemia in Preemptive Kidney Transplant Recipients

Background. Levels of fibroblast growth factor (FGF)-23, a phosphaturic hormone, increase from the early stages of CKD and are dramatically elevated in dialysis patients. Excessive FGF-23 may be involved in the hypophosphatemia and inappropriately low calcitriol levels observed after kidney transplantation (KT). This prospective observational cohort study was carried out to determine whether there are any differences in the changes in FGF-23 levels after surgery in KT recipients according to whether they were or not on dialysis before transplantation and to assess the influence of FGF-23 in the development of posttransplantation hypophosphatemia. Methods. Consecutive KT recipients at the Hospital Clinic of Barcelona were recruited. Patients developing delayed graft function were excluded. Mineral metabolism parameters, including C-terminal fragment of FGF-23, intact parathyroid hormone, and 1,25(OH)(2)D-3, were measured in 72 KT recipients (58 on dialysis before transplantation and 14 preemptive transplant recipients) at baseline, on day 15, and at 1, 3, and 6 months after transplantation. No patients received treatment with calcimimetics, bisphosphonates, vitamin D, or phosphate supplementation during the follow-up. Results. FGF-23 decreased significantly in the first month after transplantation. Baseline and FGF-23 levels within the first posttransplantation month were lower in preemptive transplant recipients than in patients on dialysis at transplantation. Serum phosphate levels were lower in dialysis patients until the third month after transplantation. Pretransplantation FGF-23 was the main predictor of posttransplantation phosphate blood levels. Conclusions. FGF-23 levels and the risk of developing posttransplantation hypophosphatemia were lower in preemptive kidney transplant recipients than in patients on dialysis before transplantation.