FGF23 and chronic kidney disease: In many human cohorts, higher circulating concentrations of total FGF23 and/or intact FGF23 have been associated with adverse clinical outcomes, including all-cause mortality [13–16], cardiovascular morbidity [8, 17–20], progression of chronic kidney disease [14, 21, 22], development of acute kidney injury (AKI) [23–28], and infection-related hospitalization [29].