title: Optimal vitamin D, calcitriol, and vitamin D analog replacement in chronic kidney disease: to D or not to D: that is the question.
abstract: OBJECTIVE
  Patients with chronic kidney disease (CKD) are often insufficient in 25(OH) vitamin D and are almost uniformly deficient in 1,25(OH)2 vitamin D, because of decreased renal hydroxylation resulting from hyperphosphatemia and elevated fibroblast growth factor-23 (FGF-23) levels. These same abnormalities lead to secondary hyperparathyroidism for which the administration of calcitriol or vitamin D analogs has been the mainstay of therapy for decades. This review summarizes new trials of vitamin D, calcitriol, and its analogs over the last 2 years.
  
  
  RESULTS
  In addition to the endocrine effects of the vitamin D axis on bone and mineral metabolism, studies have demonstrated there is also extrarenal conversion of 25(OH) vitamin D to 1,25(OH)2 vitamin D in multiple cells leading to autocrine effects. This advance has led to the speculation that CKD patients may also need to be supplemented with ergocalciferol or cholecalciferol. Unfortunately, to date, the majority of interventional studies have focused on biochemical end points. There are no randomized controlled trials demonstrating that therapy with any formulation of vitamin D results in improved patient level outcomes.
  
  
  CONCLUSIONS
  Despite the physiologic importance of vitamin D in health and disease, more research is required to determine which vitamin D derivative is required for optimal health in CKD patients.
authors.affiliation: Division of Nephrology, Indiana University School of Medicine, Roudebush Veterans Administration Medical Center, Indianapolis, Indiana 46201, USA.
authors.forename: Ranjani N
authors.initials: RN
authors.lastname: Moorthi
authors.forename: Praveen
authors.initials: P
authors.lastname: Kandula
authors.forename: Sharon M
authors.initials: SM
authors.lastname: Moe
mesh_terms: D002117:Calcitriol / Q000172:deficiency / Q000627:therapeutic use; D019587:Dietary Supplements; D019317:Evidence-Based Medicine; D000089703:Fibroblast Growth Factor-23; D006801:Humans; D006962:Hyperparathyroidism, Secondary / Q000097:blood / Q000188:drug therapy*; D007674:Kidney Diseases / Q000097:blood / Q000188:drug therapy*; D017410:Practice Guidelines as Topic; D016896:Treatment Outcome; D014807:Vitamin D / Q000031:analogs & derivatives / Q000378:metabolism / Q000627:therapeutic use*; D014808:Vitamin D Deficiency / Q000097:blood / Q000188:drug therapy*
chemical_list: C000717427:FGF23 protein, human; D014807:Vitamin D; D000089703:Fibroblast Growth Factor-23; C104450:25-hydroxyvitamin D; D002117:Calcitriol