title: Estrogen affects post-menopausal women differently than estrogen plus progestin replacement therapy.
abstract: BACKGROUND
  In the Women's Health Initiative Randomized Controlled Trial (WHI RCT), estrogen-only treatment compared with combined estrogen-progestin treatment resulted in less coronary artery disease, no increase in breast cancer and no reduction in colorectal cancer. Since we previously reasonably replicated the combined estrogen-progestin WHI RCT using the UK General Practice Research Database (GPRD), estrogen-only treatment was investigated using a similar methodology.
  
  
  METHODS
  This GPRD study simulated the estrogen-only WHI RCT of women who had undergone a hysterectomy except for randomization. The primary analysis examined 11 572 unexposed and 6890 Exposed women (aged 55-79) treated with conjugated equine estrogen and was compared with the combined estrogen-progestin GPRD study.
  
  
  RESULTS
  At baseline, women with a hysterectomy exhibited more cardiovascular disease than those with an intact uterus. In the estrogen-only GPRD study, adjusted hazard ratios (HRs) were 0.50 (0.38-0.67) for myocardial infarction (MI), 1.13 (0.91-1.41) for breast cancer, and 1.18 (0.72-1.92) for colorectal cancer. Compared to the HRs in the estrogen-progestin GPRD study, the estrogen-only results are significantly lower for MI and breast cancer and higher for colon cancer, a pattern similar to the WHI RCT study comparisons.
  
  
  CONCLUSIONS
  This study confirms that post-menopausal women in the overall population respond differently to estrogen-only treatment compared with estrogen-progestin treatment, due to different hormone regimens and/or increased cardiovascular disease in hysterectomized women.
authors.affiliation: Department of Medicine, University of Pennsylvaniua School of Medicine, 36th and Hamilton Walk, Philadelphia, PA 19104, USA. tannen@mail.med.upenn.edu
authors.forename: Richard L
authors.initials: RL
authors.lastname: Tannen
authors.forename: Mark G
authors.initials: MG
authors.lastname: Weiner
authors.forename: Dawei
authors.initials: D
authors.lastname: Xie
authors.forename: Kurt
authors.initials: K
authors.lastname: Barnhart
mesh_terms: D000368:Aged; D002318:Cardiovascular Diseases / Q000453:epidemiology*; D016208:Databases, Factual; D004359:Drug Therapy, Combination; D015914:Estrogen Replacement Therapy; D004967:Estrogens / Q000008:administration & dosage*; D005260:Female; D020249:Hormone Replacement Therapy; D006801:Humans; D007044:Hysterectomy; D008875:Middle Aged; D017698:Postmenopause / Q000187:drug effects*; D011372:Progestins / Q000008:administration & dosage*; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D004967:Estrogens; D011372:Progestins