{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,29]],"date-time":"2026-10-29T23:51:41Z","timestamp":1793317901715,"version":"4.5.0"},"reference-count":18,"publisher":"Oxford University Press (OUP)","issue":"10","license":[{"start":{"date-parts":[[2023,8,9]],"date-time":"2023-08-09T00:00:00Z","timestamp":1691539200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["asbmr.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["JBMR Plus"],"published-print":{"date-parts":[[2023,10]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:p>\n                    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\u2010mediated and non\u2010FGF23\u2010mediated renal phosphate wasting. C\u2010terminal FGF23 (cFGF23) assays detect both cFGF23 and intact FGF23 (iFGF23). Circulating FGF23 is regulated by 1.25\u2010dihydroxy\u2010vitamin D, parathyroid hormone (PTH), serum phosphate, and serum calcium but also by, for example, iron status, inflammation, erythropoietin, and hypoxia\u2010inducible\u2010factor\u20101\u2010\u03b1. We present the case of a 48\u2010year\u2010old woman with unexplained mild hypophosphatemia, very high cFGF23, and normal iFGF23. The patient proved to have an iron deficiency. Iron deficiency alters the iFGF23\u2010to\u2010cFGF23 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). \u00a9 2023 The Authors.\n                    <jats:italic>JBMR Plus<\/jats:italic>\n                    published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.\n                  <\/jats:p>","DOI":"10.1002\/jbm4.10790","type":"journal-article","created":{"date-parts":[[2023,8,10]],"date-time":"2023-08-10T01:17:32Z","timestamp":1691630252000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Case Report: Unexplained Mild Hypophosphatemia and Very High Serum FGF23 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