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]. The gene discussed is PTH; the disease is hyperphosphatemia.