FGF23 mutationsassociated with FTC cause hyperphosphataemia through effects on expression of thesodium-phosphate co-transporter in the kidney and small intestine, and throughincreased activation of vitamin D due to increased renal expression of CYP27B1(25-hydroxyvitamin-D 1 alpha hydroxylase) [40]. Here, FGF23 is linked to hyperphosphatemia.