FGF23 and chronic kidney disease: In this context, it is conceivable that reduced renal elimination of FGF23 due to declining kidney function (Mace et al., 2015), renal FGF23 resistance due to a CKD-associated downregulation of renal αKlotho expression (Shimamura et al., 2012), or increased secretion of FGF23-stimulating substances such as aldosterone or pro-inflammatory cytokines may be involved in the upregulation of blood concentrations of intact FGF23 in CKD (David et al., 2016; Erben, 2016; Kovesdy and Quarles, 2016; Zhang et al., 2016).