title: Defining a cutoff point for vitamin D deficiency based on insulin resistance in children.
abstract: BACKGROUND
  Vitamin D deficiency is a common worldwide problem. Low levels of serum 25-hydroxy vitamin D [25(OH)D], as a marker of vitamin D deficiency, have been linked to a wide field of health problems, including metabolic diseases such as insulin resistance, type 1 and type 2 DM. There is no universal definition for cutoff value of vitamin D deficiency and it seems that it varies in different populations.
  
  
  OBJECTIVE
  Most previous studies have used a start rise of PTH as a criteria to detect threshold of serum 25(OH)D, However, the aim of this study was to determine a cutoff point of serum 25(OH)D for vitamin D deficiency based on HOMA-IR.
  
  
  METHODS
  Two hundred and ninety seven healthy children (aged 7-11 years) were enrolled. Serum 25(OH)D and PTH were measured and HOMA-IR was calculated. The ROC curve was utilized to obtain a cutoff of vitamin D deficiency based on HOMA-IR.
  
  
  RESULTS
  25(OH)D concentrations were inversely correlated with HOMA-IR levels (Spearman's r=-0.14, p=0.016). Serum 25(OH)D cutoff point was 11.6ng/mL (29nmol/L) in relation with HOMA-IR >2.1. By using this cutoff value, the prevalence of vitamin D deficiency was 43.4% in this study population of healthy children.
  
  
  CONCLUSIONS
  We found that serum 25(OH)D levels are inversely associated with insulin resistance. These results suggest that in MetS patients it may benefit to determine cutoff value of 25(OH)D levels based on HOMA-IR.
authors.affiliation: Clinical Endocrinology, Zanjan Metabolic Disease Research Center, Zanjan University of Medical Sciences, Zanjan, Iran.
authors.forename: Faranak
authors.initials: F
authors.lastname: Sharifi
authors.forename: Nouraddin
authors.initials: N
authors.lastname: Mousavinasab
authors.forename: Ali Awsat
authors.initials: AA
authors.lastname: Mellati
mesh_terms: D015415:Biomarkers / Q000097:blood; D015992:Body Mass Index; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D024821:Metabolic Syndrome / Q000097:blood* / Q000517:prevention & control; D015995:Prevalence; D012372:ROC Curve; D012016:Reference Values; D012680:Sensitivity and Specificity; D014808:Vitamin D Deficiency / Q000097:blood*
chemical_list: D015415:Biomarkers
keywords: 25(OH)D; 25-Hydroxy vitamin D concentration; 25-hydroxy vitamin D; BMI; BP; Children; Cutoff point; ECLIA; FBS; FPG; GPs; HOMA-IR; HPMA-IR; IR; Insulin resistance; MetS; PTH; ROC curve; Vitamin D deficiency; WC; blood pressure; body mass index; electrochemiluminescence; fast blood sugar; fasting plasma glucose; general practitioners; homeostatic model assessment; iPTH; insulin resistance; intact parathyroid hormone; metabolic syndrome; parathyroid hormone; receiver operating characteristic curve; waist circumference