title: A cross-sectional study of vitamin D and insulin resistance in children.
abstract: OBJECTIVE
  Vitamin D deficiency is common and has been associated with several non-bone/calcium related outcomes. The objective was to determine the association between serum 25-hydroxyvitamin D (25-OH-D) and fasting glucose, insulin and insulin sensitivity in obese and non-obese children. PATIENTS/SETTING/DESIGN: Cross-sectional study of 85 children aged 4-18 years recruited from the local Philadelphia community and Sleep Center.
  
  
  METHODS
  Fasting blood glucose, insulin and 25-OH-D were measured. Insulin resistance was calculated using homeostasis model assessment (HOMA). Body mass index standard deviation scores (BMI-Z) and pubertal stage were determined. Multivariable linear regression was used to determine factors associated with decreased 25-OH-D and to determine the association of vitamin D with HOMA.
  
  
  RESULTS
  Median 25-OH-D was 52 nmol/l (IQR 34-76). 26% of subjects were vitamin D sufficient (25-OH-D ≥75 nmol/l), 27% had intermediate values (50-75 nmol/l) and 47% were insufficient (25-50 nmol/l) or frankly deficient (<25 nmol/l). In the multivariable model, older age, higher BMI-Z and African-American race were all negatively associated with 25-OH-D; summer was positively associated with 25-OH-D. Lower 25-OH-D was associated with higher fasting blood glucose, insulin and HOMA after adjustment for puberty and BMI-Z.
  
  
  CONCLUSIONS
  Low 25-OH-D, common in the paediatric population at risk for diabetes (older children, African-Americans, children with increasing BMI-Z) is associated with worse insulin resistance.
authors.affiliation: Division of Endocrinology/Diabetes, 1130 Northwest Tower, The Children's Hospital of Philadelphia, 34th & Civic Center Boulevard, Philadelphia, PA 19104, USA. kellya@email.chop.edu
authors.forename: Andrea
authors.initials: A
authors.lastname: Kelly
authors.forename: Lee J
authors.initials: LJ
authors.lastname: Brooks
authors.forename: Shayne
authors.initials: S
authors.lastname: Dougherty
authors.forename: Dean C
authors.initials: DC
authors.lastname: Carlow
authors.forename: Babette S
authors.initials: BS
authors.lastname: Zemel
mesh_terms: D000293:Adolescent; D000886:Anthropometry / Q000379:methods; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology; D008297:Male; D009765:Obesity / Q000097:blood / Q000150:complications* / Q000503:physiopathology; D012621:Seasons; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000209:etiology* / Q000503:physiopathology
chemical_list: D001786:Blood Glucose; D007328:Insulin; D014807:Vitamin D; C104450:25-hydroxyvitamin D