title: Vitamin D status and its relation to age and body mass index.
abstract: OBJECTIVE
  While numerous studies have examined 25(OH)-vitamin D(3) (25-D) concentrations and their relation to parathyroid hormone (PTH) levels there is only limited information on the interrelation between 25-D, 1,25(OH)(2)-vitamin D(3) (1,25-D) and PTH. It was the aim of this study to assess the vitamin D endocrine system and its relation to age and body mass index (BMI).
  
  
  METHODS
  This cross-sectional study comprised a convenience sample of 483 adults which attended the endocrinology outpatient service of a university hospital in the years 2002-2004.
  
  
  RESULTS
  The mean concentrations of 25-D, 1,25-D, calcium and PTH were 21.0 +/- 10.6 ng/ml, 47.9 +/- 21.7 pg/ml, 9.48 +/- 0.48 mg/dl and 51.0 +/- 27.2 pg/ml, respectively. 25-D was related (p < 0.01) to BMI, age, PTH and 1,25-D. After correction for 25-D, we found no relation between BMI and 1,25-D. PTH was related (p < 0.01) to serum calcium, BMI, age and 1,25-D (p = 0015). There was a seasonal variation in both, 25-D and 1,25-D serum concentrations: 25-D levels were lowest in January and increased until July while the nadir and zenith of 1,25-D were found in April and October, respectively.
  
  
  CONCLUSIONS
  Since BMI was negatively related to 25-D the prevalence of 25-D deficiency (<8.8 ng/ml) increased from 8.8% in subjects with BMI <30 kg/m(2) to 15.0% in subjects with BMI >30 kg/m(2). BMI, age and season should be taken into account when assessing a patients vitamin D status and more aggressive vitamin D supplementation should be considered for obese subjects.
authors.affiliation: Division of Endocrinology and Metabolism, Department of Internal Medicine III, Medical University of Vienna, Vienna, Austria. martin.bischof@meduniwien.ac.at
authors.forename: Martin G
authors.initials: MG
authors.lastname: Bischof
authors.forename: Georg
authors.initials: G
authors.lastname: Heinze
authors.forename: Heinrich
authors.initials: H
authors.lastname: Vierhapper
mesh_terms: D000328:Adult; D000367:Age Factors; D015992:Body Mass Index; D002112:Calcifediol / Q000008:administration & dosage / Q000097:blood*; D004703:Endocrine System / Q000378:metabolism; D004700:Endocrine System Diseases / Q000097:blood; D005260:Female; D006785:Hospitals, University; D006801:Humans; D008297:Male; D010045:Outpatients; D010281:Parathyroid Hormone / Q000097:blood*; D012621:Seasons; D014808:Vitamin D Deficiency / Q000097:blood*
chemical_list: C470125:PTH protein, human; D010281:Parathyroid Hormone; D002112:Calcifediol