[Significance of FGF23 measurement]

Excess and deficient actions of FGF23 cause hypophosphatemic rickets/osteomalacia and hyperphosphatemic tumoral calcinosis, respectively. There are two kinds of assays for FGF23. Full-length assay detects only full-length FGF23 with biological activity. In contrast, C-terminal assay measures both full-length FGF23 and processed C-terminal fragment of FGF23. FGF23 measurement is useful for the diagnosis and follow-up of patients with FGF23-related hypophosphatemic diseases. In addition, full-length assay can be used for the differential diagnosis of hypophosphatemic diseases. Furthermore, many epidemiological studies indicated the association between FGF23 levels and several adverse events including higher mortality, cardiovascular diseases and progression of CKD especially in patients with CKD. Therefore, it is possible that FGF23 can be a new marker in the risk assessment of patients with CKD.