It reduces renal phosphate reabsorption and inhibits 1α-hydroxylase activity, leading to suppressed 1,25(OH)2D (calcitriol) formation, which is the active form of vitamin D. FGF23 is markedly greater in chronic kidney disease (CKD) patients than in healthy populations and begin to rise in the early stages of CKD [1,2]. The gene discussed is FGF23; the disease is chronic kidney disease.