Relationship between Plasma Fibroblast Growth Factor-23 Concentration and Bone Mineralization in Children with Renal Failure on Peritoneal Dialysis

Context: Fibroblast growth factor (FGF)-23 is produced in bone, and circulating levels are markedly elevated in patients with end-stage kidney disease, but the relationship between plasma levels of FGF-23 and bone histology in dialysis patients with secondary hyperparathyroidism is unknown. Objective: The aim of the study was to evaluate the correlation between plasma levels of FGF-23 and bone histology in pediatric patients with end- stage kidney disease who display biochemical evidence of secondary hyperparathyroidism. Design: We performed a cross-sectional analysis of the relationship between plasma FGF-23 levels and bone histomorphometry. Setting: The study was conducted in a referral center. Study Participants: Participants consisted of forty-nine pediatric patients who were treated with maintenance peritoneal dialysis and who had serum PTH levels (1st generation Nichols assay) greater than 400 pg/ml. Intervention: There were no interventions. Main Outcome Measure: Plasma FGF-23 levels and bone histomorphometry were measured. Results: No correlation existed between values of PTH and FGF-23. Bone formation rates correlated with PTH (r=0.44; P < 0.01), but not with FGF-23. Higher FGF-23 concentrations were associated with decreased osteoid thickness (r=-0.49; P < 0.01) and shorter osteoid maturation time (r=-0.48; P < 0.01). Conclusions: High levels of FGF-23 are associated with improved indices of skeletal mineralization in dialyzed pediatric patients with high turnover renal osteodystrophy. Together with other biomarkers, FGF-23 measurements may indicate skeletal mineralization status in this patient population. (J Clin Endocrinol Metab 94: 511-517, 2009)