title: Association of oral but not transdermal estrogen therapy with enhanced platelet reactivity in a subset of postmenopausal women.
abstract: OBJECTIVE
  We sought to determine the effects of oral versus transdermal estrogen therapy on platelet function in postmenopausal women.
  
  
  METHODS
  Blood obtained from 84 postmenopausal women was tested for closure times using the Platelet Function Analyzer-100 before and after administration of oral or transdermal estrogen for 8 weeks.
  
  
  RESULTS
  Women with normal closure times at baseline (n = 71) demonstrated no significant change after receiving estrogen therapy with oral (n = 29) or transdermal (n = 42) estrogen. Women with borderline closure times of 61 to 66 seconds (n = 13) showed a significant acceleration of closure times (P = 0.0008) after oral estrogen therapy (-6.8 +/- 0.7 seconds, n = 5) but no significant change from baseline after transdermal estrogen therapy (1.1 +/- 0.5 seconds, n = 8).
  
  
  CONCLUSIONS
  An acceleration of closure times as measured by the Platelet Function Analyzer-100 in women with borderline baseline closure times is associated with the use of oral, but not transdermal, estrogen therapy. These results suggest that oral estrogen therapy increases platelet reactivity in a subset of women.
authors.affiliation: Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA. rflaumen@bidmc.harvard.edu
authors.forename: Robert
authors.initials: R
authors.lastname: Flaumenhaft
authors.forename: Margaret
authors.initials: M
authors.lastname: Nachtigall
authors.forename: Joanna
authors.initials: J
authors.lastname: Lowenstein
authors.forename: Lisa
authors.initials: L
authors.lastname: Nachtigall
authors.forename: Richard
authors.initials: R
authors.lastname: Nachtigall
authors.forename: Lila
authors.initials: L
authors.lastname: Nachtigall
mesh_terms: D000279:Administration, Cutaneous; D000284:Administration, Oral; D001792:Blood Platelets / Q000187:drug effects* / Q000502:physiology; D015914:Estrogen Replacement Therapy; D004967:Estrogens / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D008875:Middle Aged; D017698:Postmenopause; D016896:Treatment Outcome
chemical_list: D004967:Estrogens