In patients with moderate to advanced stage CKD, normophosphatemia is maintained by the action of FGF23 and PTH to augment phosphaturia, but the progression of CKD together with decreased expression of renal Klotho leads to a reduction in the ability of the kidney to excrete urinary phosphate, leading to the development of overt hyperphosphatemia. Here, FGF23 is linked to chronic kidney disease.