The causes of vitamin D deficiency is due to a number of factors including: (i) increased fibroblast growth factor 23 (FGF23) levels that decrease the expression and activity of 1α-hydroxylase and stimulate 24-hydroxylase that degrades 1,25 dihydroxyvitamin D [25] (ii) increase phosphate retention that inhibit the activity of 1α-hydroxylase (iii) reduced renal mass and less proximal tubular cells with 1α-hydroxylase activity and (iv) renal loss of loss of 25-hydroxyvitamin D and its binding, particularly in chronic kidney disease patients with proteinuria [26]. This evidence concerns the gene FGF23 and chronic kidney disease.