title: Serum 25-hydroxyvitamin D (25-OH-D) in obese adolescents.
abstract: BACKGROUND
  There is increasing evidence that vitamin D deficiency is common and has been associated with several non-bone related outcomes, including insulin resistance, type 2 diabetes and cardiovascular disease. The influences of gender, puberty, and adiposity on serum hydroxyvitamin D (25-OH-D) levels and the relationship between 25-OH-D and insulin resistance in obese children were studied.
  
  
  METHODS
  Age, gender, pubertal stage, weight status (standard deviation score of body mass index: BMI-SDS, percentage body fat, waist circumference), 25-OH-D levels, and insulin resistance index calculated by homeostasis model assessment (HOMA-IR) were evaluated in 64 obese adolescents. Multivariable linear regression was used to determine factors associated with decreased serum 25-OH-D levels and to study the relationship between 25-OH-D and HOMA-IR.
  
  
  RESULTS
  Median serum 25-OH-D level was 10.1 ng/mL (25.2 nmol/L). 14% of patients were vitamin D-sufficient (25-OH-D ≥ 20 ng/mL), 36% had intermediate values (11-19 ng/mL), and 50% were deficient (25-OH-D ≤ 10 ng/mL). In the multivariable model, older age, puberty, higher value of percentage of body fat, and the presence of acanthosis nigricans (AN) were all negatively associated with 25-OH-D. Lower 25-OH-D levels were also associated with higher blood glucose, insulin and HOMA-IR after adjustment for puberty and SDS-BMI. Summer positively correlated with 25-OH-D level.
  
  
  CONCLUSIONS
  Our study confirms that obesity is a risk factor for vitamin D deficiency. Hypovitaminosis D, common in obese adolescents at risk for type 2 diabetes (older age, puberty, acanthosis nigricans) is associated with worse insulin resistance.
authors.affiliation: Independent Laboratory of Propaedeutics of Children’s Diseases, Pomeranian Medical University, Szczecin, Poland. propedeutyka1@wp.pl
authors.forename: Barbara
authors.initials: B
authors.lastname: Garanty-Bogacka
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Syrenicz
authors.forename: Joanna
authors.initials: J
authors.lastname: Goral
authors.forename: Beata
authors.initials: B
authors.lastname: Krupa
authors.forename: Justyna
authors.initials: J
authors.lastname: Syrenicz
authors.forename: Mieczysław
authors.initials: M
authors.lastname: Walczak
authors.forename: Anhelli
authors.initials: A
authors.lastname: Syrenicz
mesh_terms: D000293:Adolescent; D000367:Age Factors; D015992:Body Mass Index; D002648:Child; D005260:Female; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology*; D016014:Linear Models; D008297:Male; D009765:Obesity / Q000097:blood*; D012737:Sex Factors; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood*
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D