Calcitriol (1,25 dihydroxy vitamin D3) and other active (1α-hydroxylated) forms of vitamin D can effectively suppress parathyroid hormone levels in pre-dialysis patients with CKD; however, these agents are associated with an increased risk of hypercalcaemia and ectopic calcification, and do not replenish 25(OH)D substrate levels [36]. The gene discussed is PTH; the disease is chronic kidney disease.