title: Effect of postmenopausal hormonal replacement therapy on mammographic density and parenchymal pattern.
abstract: OBJECTIVE
  To measure changes and predictors of change in mammograms obtained in postmenopausal women undergoing continuous combined hormonal replacement therapy (HRT).
  
  
  METHODS
  Mammograms of 41 postmenopausal women obtained before and 1 year after the initiation of HRT were evaluated blindly according to the quantitative density percentage method and the Wolfe classification system.
  
  
  RESULTS
  Mammographic densities increased compared with baseline values in 73% of subjects (mean increase, 6.7%; 95% confidence interval, 2.5%, 11.0%; P = .003). A shift in Wolfe classification from lower to greater parenchymal density was noted in 24% of subjects (P = .016). Multivariate analysis results indicated that the lower the tissue density percentage before treatment, the greater the increase in density percentage after treatment.
  
  
  CONCLUSIONS
  An increase in mammographic density was demonstrated in most subjects undergoing continuous combined HRT and was most pronounced in subjects with a lower baseline density percentage.
authors.affiliation: Department of Medicine, University of Washington, Seattle 98195, USA.
authors.forename: M B
authors.initials: MB
authors.lastname: Laya
authors.forename: J C
authors.initials: JC
authors.lastname: Gallagher
authors.forename: J S
authors.initials: JS
authors.lastname: Schreiman
authors.forename: E B
authors.initials: EB
authors.lastname: Larson
authors.forename: P
authors.initials: P
authors.lastname: Watson
authors.forename: L
authors.initials: L
authors.lastname: Weinstein
mesh_terms: D001940:Breast / Q000033:anatomy & histology / Q000187:drug effects*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000209:etiology; D015914:Estrogen Replacement Therapy / Q000009:adverse effects; D004966:Estrogens, Conjugated (USP) / Q000008:administration & dosage / Q000494:pharmacology; D005260:Female; D006801:Humans; D008327:Mammography / Q000706:statistics & numerical data; D017258:Medroxyprogesterone Acetate / Q000008:administration & dosage / Q000494:pharmacology; D008875:Middle Aged; D015999:Multivariate Analysis; D012307:Risk Factors
chemical_list: D004966:Estrogens, Conjugated (USP); D017258:Medroxyprogesterone Acetate