In fact, in CKD stages 3–4, daily cholecalciferol doses of 4,000 IU/day for 1 month followed by 2,000 IU for 2 additional months, which effectively corrected serum 25(OH)D from 14 to 37 ng/ml, did not reduce serum PTH, despite achieving normal serum calcitriol levels (54). This evidence concerns the gene PTH and chronic kidney disease.