title: Postmenopausal hormone replacement therapy increases plasmatic thromboxane beta 2.
abstract: OBJECTIVE
  This study shows the effect of hormone replacement therapy (HRT), using oral estrogen exclusively or in combination with progestin, on platelet activation in healthy menopaused women.
  
  
  BACKGROUND
  Recent evidence from studies of postmenopausal HRT in healthy women demonstrated a short-time increased risk of coronary heart disease. Platelet activation, which generates vasoconstrictory thromboxane A(2) (TxA(2)), has been related to the risk of cardiovascular diseases.
  
  
  METHODS
  By means of a placebo-controlled study twenty-seven postmenopausal patients were continuously orally administered estrogen in combination with progestin or estrogen exclusively for an 8-week period. Platelet activation was evaluated by flow cytometric P-selectin expression and by enzyme immunoassay plasmatic TxA(2) (TxB(2)) concentrations.
  
  
  RESULTS
  P-selectin binding index changed from 6.3+/-3.6 to 7.0+/-3 in the placebo group (n=10); from 5.9+2.2 to 7.9+/-3.3 in the E+P group (n=8) and from 6.4+2.7 to 7.1+/-1.9 in the E group (n=9). Plasma concentrations of TxB(2) before and after intervention, changed from 1.2+1.2 to 1.5+1.4 (pg/well) in the placebo group; significantly (p=0.005) in the E+P group (n=8), from 0.9+0.3 to 6.1+6.5 (pg/well), and from 1.3+1.5 to 0.8+0.4 (pg/well) in the E group (n=8; mean+standard deviation, basal x therapy, p<0.05).
  
  
  CONCLUSIONS
  Healthy menopaused women who were administered estradiol in association with norethisterone continuously had an increase of plasmatic thromboxane, possibly determined by platelet activation, which indicates a higher short-term thrombotic risk. P-selectin expression analyses failed to demonstrate the impact of HRT on platelets.
authors.affiliation: Heart Institute (InCor), University of São Paulo Medical School, 05403-900 São Paulo, Brazil. ruteloreto@bol.com.br
authors.forename: Rute Loreto S
authors.initials: RL
authors.lastname: Oliveira
authors.forename: José M
authors.initials: JM
authors.lastname: Aldrighi
authors.forename: Otávio E
authors.initials: OE
authors.lastname: Gebara
authors.forename: Tania R F
authors.initials: TR
authors.lastname: Rocha
authors.forename: Elbio
authors.initials: E
authors.lastname: D'Amico
authors.forename: Giuseppe M C
authors.initials: GM
authors.lastname: Rosano
authors.forename: José Antônio F
authors.initials: JA
authors.lastname: Ramires
mesh_terms: D000368:Aged; D015914:Estrogen Replacement Therapy; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D006801:Humans; D008875:Middle Aged; D019007:P-Selectin / Q000097:blood; D015539:Platelet Activation / Q000187:drug effects* / Q000502:physiology; D011372:Progestins / Q000494:pharmacology; D013929:Thromboxane B2 / Q000097:blood*
chemical_list: D004967:Estrogens; D019007:P-Selectin; D011372:Progestins; D013929:Thromboxane B2