FGF23 and chronic kidney disease: As will be discussed in Sections “FGF23 Signaling Is Regulated by Cleavage of Intact FGF23” and “EPO, Iron, CKD, and Inflammation Are Important Regulators of iFGF23 Cleavage,” the amount of cleavage of FGF23 is equally important and EPO has a strong effect on this as well.