A recent real-world study conducted on clinical records from 18 Nephrology clinics in the US compared the effects of nutritional vitamin D (n = 147), extended-release calcifediol (n = 174), and active vitamin D agents (n = 55) on levels of 25(OH)D, parathyroid hormone, calcium, and phosphorus levels after ≥ 20 weeks of follow-up in adults with stage 3 or 4 CKD. This evidence concerns the gene PTH and chronic kidney disease.