PTH and vitamin D deficiency: This article focuses on the position of Rayaldee®, an extended-release (in Europe the term “prolonged-release” is used) calcifediol formulation that raises 25(OH)D, lowers parathyroid hormone levels, and is approved for the treatment of secondary hyperparathyroidism in adults with CKD Stage 3 or 4 and vitamin D insufficiency or deficiency [21, 22].