title: Association between IGF1 CA microsatellites and mammographic density, anthropometric measures, and circulating IGF-I levels in premenopausal Caucasian women.
abstract: BACKGROUND
  Results from several studies indicate that mammographic density, a strong risk factor for breast cancer, is greater in premenopausal women with higher circulating IGF-I levels. Both mammographic density and circulating IGF-I levels appear to be partly heritable traits. We hypothesized that in premenopausal women, IGF1 variants are associated with circulating IGF-I concentration, which in turn influences variation in breast density. Therefore, we examined the association of IGF1 polymorphisms with circulating IGF-I levels and mammographic density.
  
  
  METHODS
  Percentage density, amounts of dense and non-dense (fat) tissue, IGF-I levels, and BMI were measured in 163 premenopausal women. Three CA repeat polymorphisms were genotyped, one each at the 5' and 3' ends of IGF1 and one in intron 2.
  
  
  RESULTS
  The number of 19 alleles at the 5' polymorphism was associated with lower circulating levels of IGF-I (P = 0.02), whereas the number of 185 alleles at the 3' polymorphism was associated with higher percentage density (P = 0.03) and a smaller amount of non-dense tissue (P = 0.02). The strength of the effect of the 185 allele at 3' on percentage density was greatly reduced and statistical significance lost when BMI was included in regression models.
  
  
  CONCLUSIONS
  Our results suggest an association between the number of 185 alleles at 3' with percentage density. This association appears to be mediated by body composition and particularly body fat, as indicated by the association of 3' IGF1 genotype with non-dense (fat) tissue and the mediating effect of BMI on the association of 3' genotype with percentage density.
authors.affiliation: Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada. gordon.fehringer@cancercare.on.ca
authors.forename: Gordon
authors.initials: G
authors.lastname: Fehringer
authors.forename: Hilmi
authors.initials: H
authors.lastname: Ozcelik
authors.forename: Julia A
authors.initials: JA
authors.lastname: Knight
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Paterson
authors.forename: Norman F
authors.initials: NF
authors.lastname: Boyd
mesh_terms: D000328:Adult; D000886:Anthropometry; D001823:Body Composition / Q000502:physiology*; D001940:Breast / Q000473:pathology*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000235:genetics; D005260:Female; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006239:Haplotypes; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis* / Q000235:genetics*; D015810:Linkage Disequilibrium; D008327:Mammography; D018895:Microsatellite Repeats; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D017697:Premenopause; D011863:Radioimmunoassay; D012307:Risk Factors; D044465:White People
chemical_list: D007334:Insulin-Like Growth Factor I