title: Effect of Calcitriol on FGF23 Level in Healthy Adults and its Dependence on Phosphate Level.
abstract: To evaluate the short-term effects of calcitriol and sevelamer hydrochloride on fibroblast growth factor-23 (FGF23) in humans and to determine whether the effect is direct or indirect through calcitriol-induced increased absorption of phosphorus from the intestine.
  
  
  
  A total of 15 healthy individuals were tested at three time points and stages, for 24 h and at 1-week intervals. During each stage, blood samples were taken at three time points (0, 8 and 24 h); baseline stage: under no intervention; second stage, while receiving 0.5 μg calcitriol orally twice daily; and at the third stage, while receiving 0.5 μg calcitriol orally twice daily and sevelamer hydrochloride during meals. The changes in FGF23, parathyroid hormone, calcitriol, Ca, and phosphorus were determined.
  
  
  
  During calcitriol administration, the FGF23 level changed significantly (p=0.008), with the level at 24 h levels being significantly higher than at 8 h (8.8 pg/ml vs. 13.0 pg/ml, p=0.036). There was a statistically significant difference in the percentage change, among the three stages, at time 8 to 24 h and 0 to 24 h for FGF23 (p=0.014 and p=0.015, respectively), with significant differences between baseline vs. calcitriol for 8 to 24 h FGF23 change (-9.23% vs. 26.98%, p=0.003) and a trend between baseline vs. calcitriol (p=0.061) and calcitriol plus sevelamer (p=0.069) for 0 to 24 h FGF23 change.
  
  
  
  Administration of calcitriol to healthy individuals increases the circulating level of FGF23 within 24 h. Combined calcitriol and sevelamer administration restrains the increase of FGF23, suggesting that calcitriol-induced increased absorption of phosphate from the intestine might also be involved in the increase of FGF23.
authors.affiliation: Th. Garofalidis Laboratory for Research of the Musculoskeletal System, Medical School, National & Kapodistrian University of Athens egeorgiadou@efet.gr.
authors.forename: Effrosyni
authors.initials: E
authors.lastname: Georgiadou
authors.affiliation: Department of Biochemistry, KAT Hospital, Athens, Greece.
authors.forename: Helen
authors.initials: H
authors.lastname: Marketou
authors.affiliation: Th. Garofalidis Laboratory for Research of the Musculoskeletal System, Medical School, National & Kapodistrian University of Athens.
authors.forename: George
authors.initials: G
authors.lastname: Trovas
authors.affiliation: Th. Garofalidis Laboratory for Research of the Musculoskeletal System, Medical School, National & Kapodistrian University of Athens.
authors.forename: Ismene
authors.initials: I
authors.lastname: Dontas
authors.affiliation: Th. Garofalidis Laboratory for Research of the Musculoskeletal System, Medical School, National & Kapodistrian University of Athens.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Papaioannou
authors.affiliation: Department of Biochemistry, KAT Hospital, Athens, Greece.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Makris
authors.affiliation: Th. Garofalidis Laboratory for Research of the Musculoskeletal System, Medical School, National & Kapodistrian University of Athens.
authors.forename: Antonios
authors.initials: A
authors.lastname: Galanos
authors.affiliation: Department of Biological Chemistry, Medical School, National & Kapodistrian University of Athens, Athens, Greece.
authors.forename: Athanasios
authors.initials: AG
authors.lastname: Papavassiliou
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood*; D050071:Bone Density Conservation Agents / Q000494:pharmacology; D002117:Calcitriol / Q000494:pharmacology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood*; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D010710:Phosphates / Q000097:blood*; D055815:Young Adult
chemical_list: D015415:Biomarkers; D050071:Bone Density Conservation Agents; C000717427:FGF23 protein, human; D010281:Parathyroid Hormone; D010710:Phosphates; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D002117:Calcitriol
keywords: Calcitriol; FGF23; healthy adults; phosphorus; sevelamer hydrochloride