The aim of this observational prospective study was to assess the effect of cholecalciferol in achieving high–normal serum 25-hydroxycholecalciferol (25(OH)D > 75 ng/mL) levels and its impact on CKD-MBD biochemical markers, including 1,25-dihydroxycholecalciferol (1,25(OH)2D) and parathormone (PTH) in HD patients. This evidence concerns the gene PTH and Marchiafava-Bignami disease.