FGF23 and anemia (phenotype): The mature bioactive form primarily functions to regulate renal phosphate excretion and vitamin D metabolism [12], circulating iFGF23 represents the full-length, biologically active isoform and is implicated in anemia progression, renal dysfunction, and mineral-bone disorders [13], In contrast, the biological role of C-terminal FGF23 (cFGF23) remains incompletely characterized.