In patients with CKD, the reduction in synthesis or activity of calcitriol by higher levels of FGF-23 and hyperphosphatemia causes hyporesponsiveness of the VDR and a reduced expression of the CaSR on the parathyroid glands, which leads to increased synthesis of PTH and parathyroid glands hyperplasia [38]. This evidence concerns the gene FGF23 and hyperphosphatemia.