The relative role of fibroblast growth factor 23 and parathyroid hormone in predicting future hypophosphatemia and hypercalcemia after living donor kidney transplantation: a 1-year prospective observational study.

Background: Kidney transplantation (KTx) restores many of the disorders accompanying end-stage renal failure. However, hypercalcemia and hypophosphatemia are both common complications after renal transplantation. Prospective observation of these complications has not been well described and pre-transplant predictors also remain unknown. This prospective observational cohort study was carried out to clarify pre-transplant risk factors of persistent hypophosphatemia and/or hypercalcemia at 12 months after transplantation.

Methods: Consecutive living donor KTx recipients (n = 39) at Tokyo Women's Medical University were prospectively recruited. Parameters of bone and mineral metabolism including intact parathyroid hormone (iPTH) and full-length fibroblast growth factor (FGF) 23 were followed.

Results: FGF23 decreased to comparable levels for renal function while hyperparathyroidism persisted at 12 months after transplantation. Multivariate linear regression analysis revealed that pre-transplant iPTH correlated with hypercalcemia at 12 months and pre-transplant FGF23 was the best pre-transplant predictor of persistent hypophosphatemia at 12 months.

Conclusions: It is intriguing that although FGF23 is not a causal factor for hypophosphatemia at 12 months post-transplantation, it is a significant predictor of this common complication.