title: Vitamin D status affects serum parathyroid hormone concentrations during winter in female adolescents: associations with forearm bone mineral density.
abstract: BACKGROUND
  Vitamin D deficiency leads to secondary hyperparathyroidism, which has a negative effect on bone metabolism in the elderly. Puberty is an important time of bone metabolism and growth. The effect of serum 25-hydroxyvitamin D [25(OH)D] concentrations on parathyroid hormone concentrations and bone mineral density (BMD) has not been well studied cross-sectionally in adolescents.
  
  
  OBJECTIVE
  We studied the effect of vitamin D status on serum intact parathyroid hormone (iPTH) concentrations and bone metabolism in adolescents.
  
  
  METHODS
  One hundred seventy-eight healthy female adolescents (aged 14-16 y) volunteered for this study, which was conducted in Finland (Helsinki, 60 degrees N) during the winter. Forearm BMD at radial and ulnar sites was measured by dual energy X-ray absorptiometry. The determinants of different variables were studied by use of regression models.
  
  
  RESULTS
  On the basis of the relation between serum 25(OH)D and iPTH concentrations, serum 25(OH)D concentrations > approximately 40 nmol/L were needed to keep serum iPTH concentrations low. One hundred ten subjects (61.8%) had serum 25(OH)D concentrations < or =40 nmol/L. Twenty-four subjects (13.5%) were considered vitamin D deficient when the serum 25(OH)D concentration of 25 nmol/L was used as a cutoff. Subjects with serum 25(OH)D concentrations < or =40 nmol/L had low mean forearm BMD values at both the radial (P = 0.04) and ulnar (P = 0.08) sites.
  
  
  CONCLUSIONS
  A large percentage of adolescent females have low vitamin D status during the winter in Finland, which seems to have negative effects on bone health.
authors.affiliation: Calcium Research Unit, the Department of Applied Chemistry and Microbiology, University of Helsinki, Finland.
authors.forename: T A
authors.initials: TA
authors.lastname: Outila
authors.forename: M U
authors.initials: MU
authors.lastname: Kärkkäinen
authors.forename: C J
authors.initials: CJ
authors.lastname: Lamberg-Allardt
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D017195:Adolescent Nutritional Physiological Phenomena; D015519:Bone Density / Q000502:physiology*; D001842:Bone and Bones / Q000378:metabolism*; D002136:Calcium, Dietary / Q000008:administration & dosage*; D003430:Cross-Sectional Studies; D005260:Female; D005387:Finland; D005542:Forearm; D006801:Humans; D010281:Parathyroid Hormone / Q000097:blood*; D012044:Regression Analysis; D012621:Seasons; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood*; D014808:Vitamin D Deficiency / Q000453:epidemiology
chemical_list: D002136:Calcium, Dietary; D010281:Parathyroid Hormone; D014807:Vitamin D; C104450:25-hydroxyvitamin D