title: Regulation of fibroblast growth factor-23 in chronic kidney disease.
abstract: BACKGROUND
  Fibroblast growth factor-23 (FGF23) is a circulating factor that regulates the renal reabsorption of inorganic phosphate (Pi) and is increased in chronic kidney disease (CKD). The aim of the current investigation was to study the regulation of FGF23 in CKD subjects with various degree of renal function. As such, we analysed the relationship between FGF23, Pi, calcium, parathyriod hormone (PTH), 25(OH) vitamin D3(25(OH)D3), 1,25(OH)2 vitamin D3(1,25(OH)2D3) and estimated glomerular filtration rate (eGFR).
  
  
  METHODS
  Intact FGF23 and other biochemical variables were analysed in 72 consecutive adult out-patients with various stages of CKD (eGFR ranging from 4-96 ml/min.) Association studies were performed using linear univariate and multivariate analysis.
  
  
  RESULTS
  FGF23 was significantly elevated at CKD stage 4 (266 +/- 315 pg/ml, P < 0.001) and 5 (702 +/- 489 pg/ml, P < 0.001) compared with CKD 1-2 (46 +/- 43 pg/ml). In CKD 4-5 an independent association between log FGF23 and Pi (P < 0.001), 25(OH)D3 (P < 0.05) as well as eGFR (P < 0.01) was observed. In contrast, in CKD 1-3 log PTH (P < 0.05) was the only independent predictor of log FGF23 in multivariate analysis. In CKD 1-5, Pi (P < 0.00001) and log PTH (P < 0.01) were explanatory variables for log FGF23 in multivariate analysis.
  
  
  CONCLUSIONS
  We conclude that serum FGF23 increases in CKD 4-5, in parallel with the emerging hyperphosphataemia. Serum Pi is the most important predictor of FGF23 when GFR is less than 30 ml/min. In contrast, our data suggest that Pi may not be an important determinant of FGF23 in normophosphataemic CKD subjects. Finally, the association between FGF23 and PTH in CKD may suggest a co-regulation that remains to be further elucidated.
authors.affiliation: Department of Medical Sciences, Uppsala University Hospital, Ing. 70, 3 tr., UAS, 75185 Uppsala, Sweden.
authors.forename: Per-Anton
authors.initials: PA
authors.lastname: Westerberg
authors.forename: Torbjörn
authors.initials: T
authors.lastname: Linde
authors.forename: Björn
authors.initials: B
authors.lastname: Wikström
authors.forename: Osten
authors.initials: O
authors.lastname: Ljunggren
authors.forename: Mats
authors.initials: M
authors.lastname: Stridsberg
authors.forename: Tobias E
authors.initials: TE
authors.lastname: Larsson
mesh_terms: D002112:Calcifediol / Q000097:blood; D002117:Calcitriol / Q000097:blood; D002118:Calcium / Q000097:blood; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood*; D005919:Glomerular Filtration Rate; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood*; D010281:Parathyroid Hormone / Q000097:blood; D010710:Phosphates / Q000097:blood
chemical_list: C000717427:FGF23 protein, human; D010281:Parathyroid Hormone; D010710:Phosphates; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D002117:Calcitriol; D002112:Calcifediol; D002118:Calcium