Bosman Ariadne, Ratsma Danielle Ma, van der Eerden Bram Cj, Zillikens M Carola
Department of Internal Medicine Erasmus MC, University Medical Center Rotterdam The Netherlands.
JBMR Plus. 2023 Aug 9;7(10):e10790. doi: 10.1002/jbm4.10790. eCollection 2023 Oct.
Fibroblast growth factor (FGF)23 is one of the major regulators of phosphate homeostasis. Hypophosphatemia can lead to muscle weakness, fatigue, and osteomalacia. In the setting of hypophosphatemia, serum FGF23 can be measured to differentiate between FGF23-mediated and non-FGF23-mediated renal phosphate wasting. C-terminal FGF23 (cFGF23) assays detect both cFGF23 and intact FGF23 (iFGF23). Circulating FGF23 is regulated by 1.25-dihydroxy-vitamin D, parathyroid hormone (PTH), serum phosphate, and serum calcium but also by, for example, iron status, inflammation, erythropoietin, and hypoxia-inducible-factor-1-α. We present the case of a 48-year-old woman with unexplained mild hypophosphatemia, very high cFGF23, and normal iFGF23. The patient proved to have an iron deficiency. Iron deficiency alters the iFGF23-to-cFGF23 ratio. After initiation of iron treatment, cFGF23 strongly decreased. This case report illustrates the limitation of cFGF23 assays and urges clinicians to be aware that cFGF23 concentrations do not necessarily reflect iFGF23 concentrations and that alternative causes for its elevation should be considered (eg, iron deficiency). © 2023 The Authors. published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.
成纤维细胞生长因子（FGF）23是磷稳态的主要调节因子之一。低磷血症可导致肌肉无力、疲劳和骨软化症。在低磷血症的情况下，可测量血清FGF23以区分FGF23介导的和非FGF23介导的肾性磷消耗。C末端FGF23（cFGF23）检测可同时检测cFGF23和完整FGF23（iFGF23）。循环中的FGF23受1,25 - 二羟维生素D、甲状旁腺激素（PTH）、血清磷和血清钙的调节，但也受例如铁状态、炎症、促红细胞生成素和缺氧诱导因子-1-α的调节。我们报告了一例48岁女性病例，其存在不明原因的轻度低磷血症、cFGF23水平极高而iFGF23水平正常。该患者被证实存在缺铁。缺铁会改变iFGF23与cFGF23的比例。开始铁剂治疗后，cFGF23大幅下降。本病例报告说明了cFGF23检测的局限性，并敦促临床医生意识到cFGF23浓度不一定反映iFGF23浓度，且应考虑其升高的其他原因（如缺铁）。© 2023作者。由Wiley Periodicals LLC代表美国骨与矿物质研究学会出版。
