title: Fibroblast growth factor 23 in hypophosphataemic HIV-positive adults on tenofovir.
abstract: OBJECTIVE
  Hypophosphataemia is common in HIV-positive patients, in particular in those using tenofovir disoproxil fumarate (TDF). Its pathogenesis is not well understood. The importance of fibroblast growth factor 23 (FGF-23), the most potent phosphaturic hormone known today, has not been studied in these patients. The aim of the study was to investigate whether FGF-23 might be involved in the aetiology of hypophosphataemia in HIV-positive patients on tenofovir.
  
  
  METHODS
  Calcium and phosphate metabolism was studied in 36 HIV-positive patients on TDF. Hypophosphataemia was defined as a serum phosphate level<0.75 mmol/L.
  
  
  RESULTS
  Fifteen patients (42%) had hypophosphataemia (group 1), and 21 had a normal serum phosphate level (group 2). The renal phosphate reabsorption threshold [tubular maximum phosphate reabsorption per glomerular filtration rate (TmP/gfr)] was significantly lower in group 1 than in group 2 (0.58 ± 0.04 vs. 0.91 ± 0.03 mmol/L, respectively; P<0.0001). The serum phosphate concentration was strongly correlated with TmP/gfr (R=0.71; P<0.0001). Both groups had normal serum FGF-23 levels, and serum phosphate and TmP/gfr were not related to serum parathyroid hormone (PTH) or FGF-23 levels.
  
  
  CONCLUSIONS
  FGF-23 is not involved in the pathogenesis of hypophosphataemia in HIV-positive patients on TDF. The data suggest that a PTH-like factor may be involved.
authors.affiliation: Department of Internal Medicine, Rijnstate Hospital, Arnhem, the Netherlands. abech@alysis.nl
authors.forename: A
authors.initials: A
authors.lastname: Bech
authors.forename: P
authors.initials: P
authors.lastname: Van Bentum
authors.forename: K
authors.initials: K
authors.lastname: Nabbe
authors.forename: J
authors.initials: J
authors.lastname: Gisolf
authors.forename: C
authors.initials: C
authors.lastname: Richter
authors.forename: H
authors.initials: H
authors.lastname: De Boer
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019380:Anti-HIV Agents / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000187:drug effects / Q000378:metabolism*; D005919:Glomerular Filtration Rate; D006679:HIV Seropositivity / Q000150:complications / Q000188:drug therapy / Q000378:metabolism*; D006801:Humans; D017674:Hypophosphatemia / Q000209:etiology / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D063065:Organophosphonates / Q000494:pharmacology*; D044162:Parathyroid Hormone-Related Protein / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D000068698:Tenofovir
chemical_list: D019380:Anti-HIV Agents; C000717427:FGF23 protein, human; D063065:Organophosphonates; D044162:Parathyroid Hormone-Related Protein; D010710:Phosphates; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D000068698:Tenofovir; D000225:Adenine; D002118:Calcium