Pleiotropic effects of vitamin D in chronic kidney disease
Low 25(OH)D levels are common in chronic kidney disease (CKD) patients and are implicated in all-cause mortality and morbidity risks. Furthermore, the progression of CKD is accompanied by a gradual decline in 25(OH)D production. Vitamin D deficiency in CKD causes skeletal disorders, such as osteoblast or osteoclast cell defects, bone turnover imbalance, and deterioration of bone quality, and nonskeletal disorders, such as metabolic syndrome, hypertension, immune dysfunction, hyperlipidemia, diabetes, and anemia. Extra-renal organs possess the enzymatic machinery for converting 25(OH)D to 1,25(OH)2D, which may play considerable biological roles beyond the traditional roles of vitamin D. Pharmacological 1,25(OH)2D dose causes hypercalcemia and hyperphosphatemia as well as adynamic bone disorder, which intensifies vascular calcification. Conversely, native vitamin D supplementation reduces the risk of hypercalcemia and hyperphosphatemia, which may play a role in managing bone and cardio–renal health and ultimately reducing mortality in CKD patients. Nevertheless, the combination of native vitamin D and active vitamin D can enhance therapy benefits of secondary hyperparathyroidism because of extra-renal 1α-hydroxylase activity in parathyroid gland. This article emphasizes the role of native vitamin D replacements in CKD, reviews vitamin D biology, and summarizes the present literature regarding native vitamin D replacement in the CKD population.