Pathogenic variants in the PHEX (phosphate-regulating neutral endopeptidase homolog X-linked) gene lead to an increased secretion of the phosphaturic hormone fibroblast growth factor 23 (FGF23) from bone, consecutive renal phosphate wasting and impaired synthesis of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), resulting in hypophosphatemia [4]. Here, FGF23 is linked to hypophosphatemia.