title: Chronic kidney disease and diabetes mellitus predict resistance to vitamin D replacement therapy.
abstract: BACKGROUND
  25-Hydroxyvitamin D [25(OH)D] is a marker of nutritional status; however, chronic kidney disease (CKD) results in alterations in vitamin D metabolism, including the loss of vitamin D-binding proteins and alterations in CYP27B1 and CYP24 enzymes that metabolize 25(OH)D. This study was designed to determine the predictors of responsiveness to correction of vitamin D deficiency with oral vitamin D2 (ergocalciferol) in adults.
  
  
  METHODS
  A retrospective study of 183 veterans with 25(OH)D level <30 ng/mL, who were treated with 50,000 IU per week of vitamin D2, was performed. Logistic regression models were developed to determine the factors predicting the response to treatment, defined as either the change in serum 25(OH)D level/1000 IU of vitamin D2 or the number of vitamin D2 doses (50,000 IU per dose) administered.
  
  
  RESULTS
  The mean age of the patients was 63 ± 12 years. About 87% were men and 51% diabetic, and 29% had an estimated glomerular filtration rate of <60 mL/min/1.73 m. The average number of vitamin D2 doses was 10.91 ± 5.95; the average increase in 25(OH)D level was 18 ± 10.80 ng/mL. 25(OH)D levels remained <30 ng/mL in 61 patients after treatment. A low estimated glomerular filtration rate and the presence of diabetes mellitus were significant independent predictors for inadequate response to vitamin D2 treatment in logistic regression models. Patients with CKD required greater amounts of vitamin D2 to achieve similar increases in 25(OH)D levels, versus non-CKD patients.
  
  
  CONCLUSIONS
  The presence of CKD and diabetes mellitus is associated with resistance to correction of 25(OH)D deficiency with vitamin D2 therapy. The underlying mechanism needs to be evaluated in prospective studies.
authors.affiliation: Veterans Affairs Medical Center, Memphis, Tennessee; Department of Medicine, Division of Nephrology, University of Tennessee Health Science Center, Memphis, Tennessee; Department of Medicine, Division of Nephrology, University of Chicago, Chicago, Illinois; Department of Medicine, Division of Nephrology, Hashemite University, Zarqa, Jordan.
authors.forename: Hala M
authors.initials: HM
authors.lastname: Alshayeb
authors.affiliation: Veterans Affairs Medical Center, Memphis, Tennessee; Department of Medicine, Division of Nephrology, University of Tennessee Health Science Center, Memphis, Tennessee. Electronic address: Barry.Wall@va.gov.
authors.forename: Barry M
authors.initials: BM
authors.lastname: Wall
authors.affiliation: Department of Medicine, Division of Nephrology, University of Tennessee Health Science Center, Memphis, Tennessee.
authors.forename: Arif
authors.initials: A
authors.lastname: Showkat
authors.affiliation: Department of Medicine, Division of Nephrology, University of Tennessee Health Science Center, Memphis, Tennessee.
authors.forename: L Darryl
authors.initials: LD
authors.lastname: Quarles
authors.affiliation: Veterans Affairs Medical Center, Memphis, Tennessee.
authors.forename: Therese
authors.initials: T
authors.lastname: Mangold
mesh_terms: D000368:Aged; D048909:Diabetes Complications / Q000150:complications / Q000188:drug therapy*; D004351:Drug Resistance; D004872:Ergocalciferols / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D051436:Renal Insufficiency, Chronic / Q000150:complications*; D012189:Retrospective Studies; D014808:Vitamin D Deficiency / Q000188:drug therapy*; D014815:Vitamins / Q000627:therapeutic use*
chemical_list: D004872:Ergocalciferols; D014815:Vitamins