FGF23 and hyperphosphatemia: Specific deletion of Klotho in distal tubules has also been reported to inhibit the increase in renal Pi excretion in response to FGF23 (89), which suggests that Klotho deficiency limits its regulation of FGF23 production and that hyperphosphataemia, which usually become evident in CKD stage 3, remains the principal regulator of FGF23 secretion in CKD (90).