title: Impaired GFR is the most important determinant for FGF-23 increase in chronic kidney disease.
abstract: OBJECTIVE
  It is unclear whether fibroblast growth factor-23 (FGF-23) increases in response to phosphate accumulation or to decrease clearance in chronic kidney disease (CKD) as is the case with other low molecular weight proteins such as cystatin C (CysC).
  
  
  METHODS
  This cross-sectional study measured serum FGF-23, CysC, and other serum markers of bone metabolism in 69 patients, aged 18 months-24 years, with various stages of CKD (eGFR=11-214mL/min).
  
  
  RESULTS
  FGF-23 levels were significantly correlated with CysC and parathyroid hormone levels (PTH) on univariate non-linear regression analysis. In multivariate linear regression analysis, log (CysC) (β=0.660, p<0.0001), log (PTH) (β=0.038, p=0.37), and phosphate (β=0.222, p=0.028) explained 69.1% of the variance of FGF-23.
  
  
  CONCLUSIONS
  CysC had the largest unique contribution to FGF-23 variance in this model, supporting the hypothesis that renal clearance may be the most responsible factor for elevated FGF-23 levels in early stages of CKD.
authors.affiliation: Department of Pediatrics, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON, Canada N6A 5W9. guido.filler@lhsc.on.ca
authors.forename: Guido
authors.initials: G
authors.lastname: Filler
authors.forename: Daisy
authors.initials: D
authors.lastname: Liu
authors.forename: Shih-Han Susan
authors.initials: SH
authors.lastname: Huang
authors.forename: Shelley
authors.initials: S
authors.lastname: Casier
authors.forename: Luan A
authors.initials: LA
authors.lastname: Chau
authors.forename: Joaquín
authors.initials: J
authors.lastname: Madrenas
mesh_terms: D003430:Cross-Sectional Studies; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood*; D005919:Glomerular Filtration Rate; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood / Q000503:physiopathology*
chemical_list: C000717427:FGF23 protein, human; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23