title: Long-term estrogen therapy improves vascular function in male to female transsexuals.
abstract: OBJECTIVE
  This study sought to examine the effects of long-term estrogen therapy on vascular function in male to female transsexuals and to compare the findings with those observed in men and premenopausal women.
  
  
  BACKGROUND
  Gender differences in coronary artery disease have largely been attributed to the beneficial effects of estrogen on vascular function and plasma lipids in women. However, the effects of estrogen on the male vasculature have not been widely studied.
  
  
  METHODS
  We compared the effects of estrogen on vascular function in 14 male to female transsexuals, 14 age-matched men and 15 premenopausal women. Flow-mediated vasodilation and response to nitroglycerin were assessed in the brachial artery using noninvasive ultrasound.
  
  
  RESULTS
  Flow-mediated vasodilation was similar in transsexuals and women but greater than that in men ([mean +/- SE] 11.5 +/- 1.3% and 9.4 +/- 1.1% vs. 5.2 +/- 1.0% respectively, p < 0.005). Responses to nitroglycerin were also greater in transsexuals and women than in men (21.6 +/- 1.7% and 21.0 +/- 0.9% vs. 14.5 +/- 1.2%, respectively, p = 0.0005). These differences persisted even after adjusting for vessel size. Despite similar total cholesterol levels, transsexuals had high density lipoprotein cholesterol levels similar to those in women and greater than those observed in men (1.76 +/- 0.12 and 1.82 +/- 0.11 mmol/liter vs. 1.35 +/- 0.07 mmol/liter, respectively, p < 0.005). Moreover, triglyceride levels were greater in transsexuals than in men and women, and low density lipoprotein cholesterol (LDL-C) particle size was smaller (25.7 +/- 0.2 nm vs. 26.2 +/- 0.1 and 26.6 +/- 0.1 nm, respectively, p = 0.0001). Serum testosterone (an index of estrogen therapy in transsexuals) was markedly suppressed in transsexuals and similar to that in women. Univariate analysis revealed that there was a strong inverse correlation between serum testosterone and flow-mediated vasodilation (r(s) = -0.48, p < 0.005). Multivariate analysis revealed that the best combination of predictors of flow-mediated vasodilation was serum testosterone, vessel size and LDL-C (R2 = 0.3, p < 0.005).
  
  
  CONCLUSIONS
  Long-term estrogen therapy appears to improve vascular function in male to female transsexuals and occurs despite higher triglyceride levels and the presence of small, dense LDL-C. The beneficial effects of estrogen are not gender specific or solely mediated through endothelium-derived nitric oxide.
authors.affiliation: Cardiovascular Centre, Monash Medical Centre, Clayton, Melbourne, Australia.
authors.forename: G
authors.initials: G
authors.lastname: New
authors.forename: K L
authors.initials: KL
authors.lastname: Timmins
authors.forename: S J
authors.initials: SJ
authors.lastname: Duffy
authors.forename: B T
authors.initials: BT
authors.lastname: Tran
authors.forename: R C
authors.initials: RC
authors.lastname: O'Brien
authors.forename: R W
authors.initials: RW
authors.lastname: Harper
authors.forename: I T
authors.initials: IT
authors.lastname: Meredith
mesh_terms: D000328:Adult; D001808:Blood Vessels / Q000187:drug effects* / Q000502:physiology; D008078:Cholesterol, LDL / Q000097:blood; D003430:Cross-Sectional Studies; D045166:Estradiol Congeners / Q000494:pharmacology* / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013739:Testosterone / Q000097:blood; D014189:Transsexualism; D014280:Triglycerides / Q000097:blood; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D008078:Cholesterol, LDL; D045166:Estradiol Congeners; D014280:Triglycerides; D013739:Testosterone