FGF23 and Hypocalcemia: Patients with CKD have 1,25-dihydroxyvitamin D deficiency due to increased production of fibroblast growth factor 23 (FGF23) and some also have a 25hydroxyD deficiency due to loss of the 1-alpha-hydroxylase enzyme from structural renal compromise, and these deficiencies predispose to hypocalcemia, which could explain the higher prevalence of a prolonged QTC20,21.