title: Fibroblast Growth Factor-23 and Vitamin D Metabolism in Subjects with eGFR ≥60 ml/min/1.73 m².
abstract: OBJECTIVE
  Fibroblast growth factor (FGF)-23 and parathyroid hormone (PTH) are both potent phosphaturic hormones. Since they exert opposite effects on vitamin D metabolism, the measurement of 3 vitamin D metabolites; 25-hydroxyvitamin D (25-OH-D), 1,25-dihydroxyvitamin D (1,25(OH)2D), and 24,25-dihydroxyvitamin D (24,25(OH)2D), allows the distinction of the effects of FGF-23 from those of PTH. The aim of this study was to elucidate which factor, FGF-23 or PTH, plays a more important role in the regulation of vitamin D metabolites in subjects with estimated glomerular filtration (eGFR) ≥60 ml/min/1.73 m(2).
  
  
  METHODS
  Subjects with eGFR ≥60 ml/min/1.73 m(2) (n = 20) were enrolled and their serum levels of FGF-23, intact PTH, and vitamin D metabolites were determined.
  
  
  RESULTS
  Serum FGF-23 correlated inversely with 1,25(OH)2D (r = -0.717, p = 0.0004) and the 1,25(OH)2D/25-OH-D ratio (r = -0.518, p = 0.019), compared with a significant positive correlation between serum intact PTH and the 1,25(OH)2D/25-OH-D ratio (r = 0.562, p = 0.010). Multiple regression analyses revealed serum FGF-23 as a significant factor that was associated with serum 1,25(OH)2D (β = -0.593, p = 0.018), 1,25(OH)2D/25-OH-D ratio (β = -0.521, p = 0.025), and the 24,25(OH)2D/1,25(OH)2D ratio (β = 0.632, p = 0.008), and intact PTH as a significant factor associated with the 1,25(OH)2D/25-OH-D ratio (β = 0.445, p = 0.028).
  
  
  CONCLUSIONS
  This study demonstrated that, even in subjects with eGFR ≥60 ml/min/1.73 m(2), FGF-23 might play an important role in the regulation of vitamin D metabolism. In addition to the established role of PTH, the association between FGF-23 and indices of vitamin D metabolism suggested the potential role of FGF-23 on phosphate metabolism in such patients.
authors.affiliation: Department of Metabolism, Endocrinology, and Molecular Medicine, Osaka City University Graduate School of Medicine, Osaka, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Nakatani
authors.forename: Ayumi
authors.initials: A
authors.lastname: Nakatani
authors.forename: Naoko
authors.initials: N
authors.lastname: Tsugawa
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Yamada
authors.forename: Katsuhito
authors.initials: K
authors.lastname: Mori
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Imanishi
authors.forename: Eiji
authors.initials: E
authors.lastname: Ishimura
authors.forename: Toshio
authors.initials: T
authors.lastname: Okano
authors.forename: Masaaki
authors.initials: M
authors.lastname: Inaba
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D004872:Ergocalciferols / Q000097:blood; D005260:Female; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000378:metabolism*; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood / Q000378:metabolism*
chemical_list: D004872:Ergocalciferols; C000717427:FGF23 protein, human; D014807:Vitamin D; C003564:1,25-dihydroxyergocalciferol; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; C104450:25-hydroxyvitamin D