title: Intravenous calcitriol therapy increases serum concentrations of fibroblast growth factor-23 in dialysis patients with secondary hyperparathyroidism.
abstract: OBJECTIVE
  Fibroblast growth factor-23 (FGF-23) is a recently discovered phosphaturic factor. Although increased levels of serum FGF-23 have been reported in dialysis patients, the role of high FGF-23 levels remains unclear. Since FGF-23 is associated also with vitamin D metabolism, we examined the changes of serum FGF-23 levels in chronic dialysis patients treated with intravenous calcitriol therapy.
  
  
  METHODS
  Thirty patients with severe secondary hyperparathyroidism were treated with intravenous calcitriol (0.5-1.0 microg) two or three times per week for 6 months. The changes of serum levels of calcium, phosphate, intact PTH, and FGF-23 were evaluated.
  
  
  RESULTS
  Baseline serum FGF-23 levels were markedly high. By intravenous calcitriol therapy, intact PTH levels decreased effectively in the first month (p < 0.001). In contrast, FGF-23 levels increased gradually during the study period (p = 0.027). The Delta serum FGF-23 level was significantly correlated with the total doses of calcitriol injected intravenously in 6 months in patients with refractory secondary hyperparathyroidism (R2 = 0.147; p = 0.036).
  
  
  CONCLUSIONS
  Intravenous calcitriol decreased serum intact PTH level and increased serum FGF-23 levels significantly. Extremely high levels of serum FGF-23 in these patients may be attributed, at least in part, to the cumulative dose of vitamin D.
authors.affiliation: Division of Nephrology and Dialysis Center, Kobe University School of Medicine, Kobe, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nishi
authors.forename: Tomoko
authors.initials: T
authors.lastname: Nii-Kono
authors.forename: Shohei
authors.initials: S
authors.lastname: Nakanishi
authors.forename: Yuji
authors.initials: Y
authors.lastname: Yamazaki
authors.forename: Takeyoshi
authors.initials: T
authors.lastname: Yamashita
authors.forename: Seiji
authors.initials: S
authors.lastname: Fukumoto
authors.forename: Kazuto
authors.initials: K
authors.lastname: Ikeda
authors.forename: Akira
authors.initials: A
authors.lastname: Fujimori
authors.forename: Masafumi
authors.initials: M
authors.lastname: Fukagawa
mesh_terms: D002117:Calcitriol / Q000008:administration & dosage*; D005260:Female; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood*; D006801:Humans; D006962:Hyperparathyroidism, Secondary / Q000097:blood* / Q000188:drug therapy*; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D006435:Renal Dialysis
chemical_list: C000717427:FGF23 protein, human; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D002117:Calcitriol