title: The association between IGF-I and insulin resistance: a general population study in Danish adults.
abstract: OBJECTIVE
  IGF-I has an almost 50% amino acid sequence homology with insulin and elicits nearly the same hypoglycemic response. Studies showed that low and high IGF-I levels are related to impaired glucose tolerance and to a higher risk of type 2 diabetes. The aim of the current study was to evaluate the association between IGF-I level and insulin resistance in a Danish general population.
  
  
  METHODS
  Included were 3,354 adults, aged 19-72 years, from the cross-sectional Health2006 study. The homeostasis model assessment of insulin resistance (HOMA-IR) was used as the index to estimate insulin resistance. Serum IGF-I levels were determined by an immunoassay and grouped into quintiles (Q1-Q5). Linear or multinomial logistic regression analyses were performed.
  
  
  RESULTS
  In the study population, 520 subjects (15.5%) had increased HOMA-IR values above 2.5. After adjustment for age, sex, physical activity, and waist-to-height ratio, a U-shaped association between IGF-I and HOMA-IR was found. Low IGF-I (Q1: odds ratio [OR] 1.65 [95% CI 1.16-2.34], P < 0.01) as well as high IGF-I (Q5: 1.96 [1.38-2.79], P < 0.01) levels were related to a higher odds of increased HOMA-IR values compared with subjects with intermediate (Q3) IGF-I levels. These associations remained statistically significant after the exclusion of subjects with type 2 diabetes and by using the updated computer HOMA2-IR model.
  
  
  CONCLUSIONS
  Low- and high-normal IGF-I levels are both related to insulin resistance. The biological mechanism of this complex phenomenon has to be elucidated in more detail for future risk stratification.
authors.affiliation: Institute of Clinical Chemistry and Laboratory Medicine, University Medicine Greifswald, Greifswald, Germany. nele.friedrich@uni-greifswald.de
authors.forename: Nele
authors.initials: N
authors.lastname: Friedrich
authors.forename: Betina
authors.initials: B
authors.lastname: Thuesen
authors.forename: Torben
authors.initials: T
authors.lastname: Jørgensen
authors.forename: Anders
authors.initials: A
authors.lastname: Juul
authors.forename: Christin
authors.initials: C
authors.lastname: Spielhagen
authors.forename: Henri
authors.initials: H
authors.lastname: Wallaschofksi
authors.forename: Allan
authors.initials: A
authors.lastname: Linneberg
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D003718:Denmark / Q000453:epidemiology; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D011153:Population; D012307:Risk Factors; D055815:Young Adult
chemical_list: D007334:Insulin-Like Growth Factor I