title: Seasonality of vitamin D status and bone turnover in patients with Crohn's disease.
abstract: BACKGROUND
  While winter-time vitamin D deficiency has been well-documented in Crohn's disease patients, less is known about vitamin D status during summertime and whether a seasonal variation exists in bone turnover.
  
  
  OBJECTIVE
  To compare vitamin D status and bone turnover markers in Crohn's disease patients with age- and sex-matched controls during late-summer and late-winter.
  
  
  METHODS
  Crohn's disease patients (n = 44; mean age 36.9 years, currently in remission) and matched controls (n = 44) were recruited from Cork University Hospital and Cork City area, respectively.
  
  
  METHODS
  Bloods were analysed for 25-hydroxyvitamin D, parathyroid hormone, bone-specific alkaline phosphatase, osteocalcin and urine analysed for N-telopeptides of type 1 collagen.
  
  
  RESULTS
  Serum 25-hydroxyvitamin D concentrations were significantly (P < 0.003) lower in Crohn's disease patients than in control subjects during both seasons. In Crohn's disease patients, serum 25-hydroxyvitamin D concentrations were lower (P < 0.0001) whereas serum parathyroid hormone, osteocalcin and bone-specific alkaline phosphatase and urinary N-telopeptides of type 1 collagen levels were higher (P < 0.001) during late-winter than late-summer.
  
  
  CONCLUSIONS
  There were notable seasonal variations in vitamin D status and bone turnover markers in Crohn's disease patients. The impact of winter decline in vitamin D status and increase in bone turnover on long-term risk of osteopenia/osteoporosis in Crohn's disease patients is unclear.
authors.affiliation: Department of Food and Nutritional Sciences, University College, Cork, Ireland.
authors.forename: D
authors.initials: D
authors.lastname: McCarthy
authors.forename: P
authors.initials: P
authors.lastname: Duggan
authors.forename: M
authors.initials: M
authors.lastname: O'Brien
authors.forename: M
authors.initials: M
authors.lastname: Kiely
authors.forename: J
authors.initials: J
authors.lastname: McCarthy
authors.forename: F
authors.initials: F
authors.lastname: Shanahan
authors.forename: K D
authors.initials: KD
authors.lastname: Cashman
mesh_terms: D000328:Adult; D016723:Bone Remodeling / Q000502:physiology*; D002118:Calcium / Q000008:administration & dosage; D016022:Case-Control Studies; D003424:Crohn Disease / Q000097:blood* / Q000150:complications / Q000503:physiopathology; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D008297:Male; D010281:Parathyroid Hormone / Q000097:blood; D012621:Seasons; D014807:Vitamin D / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood*; D014808:Vitamin D Deficiency / Q000097:blood / Q000209:etiology* / Q000503:physiopathology
chemical_list: D010281:Parathyroid Hormone; D014807:Vitamin D; C104450:25-hydroxyvitamin D; D002118:Calcium