There is an urgent, unmet need for agents that can control parathyroid hormone levels and manage secondary hyperparathyroidism by optimizing serum 25(OH)D levels in pre-dialysis CKD patients who have vitamin D insufficiency or deficiency, without perturbing calcium and phosphate equilibrium or inducing excessive release of FGF23. This evidence concerns the gene FGF23 and secondary hyperparathyroidism.