Journal of Bone and Mineral Metabolism

, Volume 23, Issue 6, pp 435–440 | Cite as

Comparison of two assays for fibroblast growth factor (FGF)-23

  • Nobuaki Ito
  • Seiji Fukumoto
  • Yasuhiro Takeuchi
  • Toshiyuki Yasuda
  • Yukihiro Hasegawa
  • Fumi Takemoto
  • Toshihiro Tajima
  • Kazushige Dobashi
  • Yuji Yamazaki
  • Takeyoshi Yamashita
  • Toshiro Fujita
ORIGINAL ARTICLE

Abstract

FGF-23 was recently shown to be involved in the development of several hypophosphatemic diseases, including X-linked hypophosphatemic rickets/osteomalacia (XLH) and tumor-induced rickets/osteomalacia (TIO). FGF-23 is processed between Arg179 and Ser180, and only full-length FGF-23 was shown to cause hypophosphatemia. Two assays for FGF-23 have been reported. One assay detects only full-length FGF-23. In contrast, the C-terminal assay recognizes both full-length and processed C-terminal fragment of FGF-23. However, discrepant results concerning circulatory levels of FGF-23 in patients with TIO and XLH have been reported using these two assays. We simultaneously measured FGF-23 levels in 13 patients with adult-onset hypophosphatemic osteomalacia and 29 patients with XLH by these two assays. The full-length assay indicated that FGF-23 was above the upper limit of the reference range in all patients with osteomalacia and in 24 of 29 patients with XLH. However, the C-terminal assay in dicated that FGF-23 was within the reference range in 3 of 13 patients with osteomalacia and 16 of 29 patients with XLH. In addition, there was no correlation between FGF-23 levels measured by these assays in patients with XLH whose FGF-23 was within the reference range by C-terminal assay. These results indicate that FGF-23 within the reference range by C-terminal assay does not rule out an increase in full-length FGF-23. In addition, because FGF-23 was high in most of these hypophosphatemic patients, these results support the notion that FGF-23 plays a major role in the development of hypophosphatemia in patients with TIO and XLH.

Key words

FGF-23 Hypophosphatemia Rickets Osteomalacia 

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Copyright information

© Springer-Verlag Tokyo 2005

Authors and Affiliations

  • Nobuaki Ito
    • 1
  • Seiji Fukumoto
    • 1
  • Yasuhiro Takeuchi
    • 1
  • Toshiyuki Yasuda
    • 2
  • Yukihiro Hasegawa
    • 3
  • Fumi Takemoto
    • 4
  • Toshihiro Tajima
    • 5
  • Kazushige Dobashi
    • 6
  • Yuji Yamazaki
    • 7
  • Takeyoshi Yamashita
    • 7
  • Toshiro Fujita
    • 1
  1. 1.Division of Nephrology and Endocrinology, Department of Internal MedicineUniversity of TokyoTokyoJapan
  2. 2.Department of Pediatrics, National Hospital OrganizationChiba Medical CenterChibaJapan
  3. 3.Endocrinology, Metabolism and Genetics UnitTokyo Metropolitan Kiyose Children's HospitalTokyoJapan
  4. 4.Department of NephrologyToranomon HospitalTokyoJapan
  5. 5.Department of PediatricsHokkaido University School of MedicineSapporoJapan
  6. 6.Department of PediatricsUniversity of Occupational and Environmental HealthKitakyushuJapan
  7. 7.Pharmaceutical Research LaboratoriesKirin Brewery Co.TakasakiJapan

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