The relationship between circulating fibroblast growth factor 23 and bone metabolism factors in Korean hemodialysis patients.

ABSTRACT

BACKGROUND: Fibroblast growth factor 23 (FGF-23) is a circulating factor that acts as a phosphaturic factor in the kidneys. It is also involved in several disorders of phosphate regulation and bone metabolism. We hypothesized that increased FGF-23 levels in patients with endstage renal disease (ESRD) on maintenance hemodialysis would be associated with increased bone demineralization, and we analyzed the relationship between FGF-23 levels and bone mineral density (BMD). METHODS: The serum level of FGF-23 was measured in this cross-sectional study, whose subjects consisted of 54 patients with ESRD on maintenance hemodialysis. Clinical parameters associated with hemodialysis and bone metabolism were measured. The relationship between serum FGF-23 and BMD and the factors affecting the serum level of FGF-23 were analyzed. RESULTS: Serum FGF-23 levels were significantly higher in ESRD patients on maintenance hemodialysis than in normal persons (2961.4 vs. 30 pg/ml). Multiple regression analysis showed that increasing FGF-23 levels were associated with serum phosphate (r = 0.684, P < 0.001), but not with BMD or other bone metabolism factors. Factors affecting log(10)FGF-23 included the serum calcium phosphate product (beta = 0.603) and K (t)/V (integrated fractional clearance expressed per dialysis, beta = -0.244). These results were also seen in an analysis of the correlations based on T score or gender. CONCLUSIONS: FGF-23 levels were positively associated with serum phosphate levels but were not correlated with BMD. The only factors affecting log(10)FGF-23 were the serum calcium phosphate product and K (t)/V. These findings suggest that FGF-23 may have no direct effect on bone mineralization, and further studies are warranted to examine the effects of FGF-23 on vitamin D metabolism.