Fibroblast growth factor 23 in oncogenic osteomalacia and X-linked hypophosphatemia

N Engl J Med. 2003 Apr 24;348(17):1656-63. doi: 10.1056/NEJMoa020881.


Background: Mutations in fibroblast growth factor 23 (FGF-23) cause autosomal dominant hypophosphatemic rickets. Clinical and laboratory findings in this disorder are similar to those in oncogenic osteomalacia, in which tumors abundantly express FGF-23 messenger RNA, and to those in X-linked hypophosphatemia, which is caused by inactivating mutations in a phosphate-regulating endopeptidase called PHEX. Recombinant FGF-23 induces phosphaturia and hypophosphatemia in vivo, suggesting that it has a role in phosphate regulation. To determine whether FGF-23 circulates in healthy persons and whether it is elevated in those with oncogenic osteomalacia or X-linked hypophosphatemia, an immunometric assay was developed to measure it.

Methods: Using affinity-purified, polyclonal antibodies against [Tyr223]FGF-23(206-222)amide and [Tyr224]FGF-23(225-244)amide, we developed a two-site enzyme-linked immunosorbent assay that detects equivalently recombinant human FGF-23, the mutant form in which glutamine is substituted for arginine at position 179 (R179Q), and synthetic human FGF-23(207-244)amide. Plasma or serum samples from 147 healthy adults (mean [+/-SD] age, 48.4+/-19.6 years) and 26 healthy children (mean age, 10.9+/-5.5 years) and from 17 patients with oncogenic osteomalacia (mean age, 43.0+/-13.3 years) and 21 patients with X-linked hypophosphatemia (mean age, 34.9+/-17.2 years) were studied.

Results: Mean FGF-23 concentrations in the healthy adults and children were 55+/-50 and 69+/-36 reference units (RU) per milliliter, respectively. Four patients with oncogenic osteomalacia had concentrations ranging from 426 to 7970 RU per milliliter, which normalized after tumor resection. FGF-23 concentrations were 481+/-528 RU per milliliter in those with suspected oncogenic osteomalacia and 353+/-510 RU per milliliter (range, 31 to 2335) in those with X-linked hypophosphatemia.

Conclusions: FGF-23 is readily detectable in the plasma or serum of healthy persons and can be markedly elevated in those with oncogenic osteomalacia or X-linked hypophosphatemia, suggesting that this growth factor has a role in phosphate homeostasis. FGF-23 measurements might improve the management of phosphate-wasting disorders.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Amino Acid Sequence
  • Child
  • Child, Preschool
  • Enzyme-Linked Immunosorbent Assay / methods
  • Female
  • Fibroblast Growth Factor-23
  • Fibroblast Growth Factors / blood*
  • Fibroblast Growth Factors / chemistry
  • Fibroblast Growth Factors / genetics
  • Genetic Diseases, X-Linked / blood
  • Humans
  • Hypophosphatemia, Familial / blood*
  • Hypophosphatemia, Familial / genetics
  • Male
  • Middle Aged
  • Molecular Sequence Data
  • Mutation
  • Osteomalacia / blood*
  • Paraneoplastic Syndromes / blood*
  • Reference Values
  • Rickets / blood
  • Rickets / genetics


  • FGF23 protein, human
  • Fibroblast Growth Factors
  • Fibroblast Growth Factor-23