Platelet activation status decreases after menopause.

Objective: The aim of the study was to investigate the impact of the climacterium (before and after menopause) on platelet activation.

Background: Platelet activation has been associated to the risk of cardiovascular disease. There is much speculation about the relationship between platelet function and sex steroids, due to peculiarities of platelet action between the genders, including concerns about the influence of low estradiol status in menopausal women.

Methods: By means of a cross-sectional study design, 37 female patients divided into two groups were compared. Group A consisted of ten women, mean age 43.9 years, in the premenopausal period, with normal estrogen levels; and Group B comprised 27 patients, mean age 53.0 years, who had all reached menopause. Platelet activation markers, namely P-selectin and glycoprotein IIb-IIIa complex (GPIIb-IIIa), were evaluated by flow cytometry with monoclonal antibodies. A binding index was calculated for both parameters (percentage of positive platelets x mean fluorescence of positive platelets). Also, thromboxane A2 was quantified by means of its main plasma metabolite, thromboxane B2, by enzyme immunoassay.

Results: P-selectin and GPIIb-IIIa expression results revealed lower platelet activation status after menopause, as there was a decrease in both the percentage of P-selectin+ platelets and of GPIIb-IIIa mean fluorescence of positive platelets, lowering both binding indices. P-selectin binding index differed significantly between Group A (12.3 +/- 3, n = 10) and Group B (6.2 +/- 2.9, n = 27; mean +/- standard deviation (SD), p < 0.001). GPIIb-IIIa binding index also differed significantly between both groups (Group A: 18.8 +/- 2.3, n = 10 vs. Group B: 16.2 +/- 3.1, n = 27; mean +/- SD, p < 0.0018). Plasma concentration of thromboxane B2 was 1.07 +/- 0.5 pg/well before menopause (Group A, n = 10) and 1.9 +/- 4.1 pg/well after menopause (Group B, n = 27), not significantly different (mean +/- SD, baseline x therapy, p = 0.85).

Conclusions: After the menopause, climacteric women--whose estradiol status is low--have a decreased activation platelet status compared with premenopausal women. Nevertheless, further studies on a larger sample are necessary for conclusive data regarding cardiovascular disease.