Determination of the elimination half-life of fibroblast growth factor-23

Context: Tumor-induced osteomalacia (TIO) is a rare paraneoplastic disease caused by mesenchymal tumors that secrete fibroblast growth factor-23 (FGF-23), a newly-described vitamin D and phosphate-regulating hormone. Surgical removal of the tumor, the ectopic source of circulating FGF-23, offers the opportunity to determine the elimination half-life of FGF-23. Objective: The aim of the study was to determine the elimination half-life of FGF-23. Patients/Methods: The tumors were removed from three patients with TIO, and serum samples were taken every 30 min for up to 72 h after the operation. FGF-23 was measured by both a C-terminal/intact assay and an intact assay, and the elimination half-life was determined by one phase exponential decay methodology. Setting: The Mark O. Hatfield Clinical Research Center of the National Institutes of Health, a tertiary referral clinical research center, was the setting for the study. Results: The elimination life of FGF-23 as determined by C-terminal/intact and intact assays was 46 +/- 12 and 58 +/- 34 min, respectively. Conclusions: The plasma half-life of serum FGF-23 is in the range of 46-58 min.