Fibroblast growth factor 23 (FGF23) is a 251-amino-acid protein secreted by osteocytes in adults[6], and it is an important regulator that maintains serum phosphorus levels within the normal range in patients with CKD by increasing urinary phosphate excretion and decreasing dietary phosphorus absorption through the inhibition of 1,25-dihydroxyvitamin D (1,25(OH)2D) synthesis[7]. The gene discussed is FGF23; the disease is chronic kidney disease.