Endometrial blood flow response to estrogen replacement therapy and tamoxifen in asymptomatic, postmenopausal women: a transvaginal Doppler study

This study was conducted to evaluate endometrial blood flow characteristics in response to estrogen replacement therapy (ERT) and tamoxifen in asymptomatic postmenopausal women, and to correlate the resistance index (RI) with plasma estradiol levels. Transvaginal color Doppler ultrasound examinations were performed in 30 asymptomatic, postmenopausal women who demonstrated thin endometria (< 0.5 cm). Ten healthy women receiving ERT and ten women with breast cancer receiving tamoxifen comprised the study groups. Ten postmenopausal women free of any hormonal treatment comprised the control group. Blood flow response was assessed by visualization of arterial waveforms in the endometrial region. Resistance indices were calculated for analysis and correlated with peripheral blood levels of estradiol. All postmenopausal women treated with tamoxifen or ERT showed continuous forward end‐diastolic flow velocities, while the menopausal women without treatment demonstrated partial forward end‐diastolic flow. Resistance index values of non‐treated women were invariably higher (mean 0.89, range 0.85–0.91) than in those on tamoxifen (mean 0.79, range 0.54–0.90; p < 0.05), while the lowest RI was obtained in women taking ERT (mean 0.66, range 0.54–0.90; p < 0.05). The plasma concentrations of estradiol in women on ERT were found to be significantly higher than those of the tamoxifen and control groups. The observed data suggest that ERT and tamoxifen modify normal postmenopausal endometrial perfusion. Tamoxifen had a weaker estrogenic effect on the endometrial blood flow resistance, and ERT enhanced endometrial blood perfusion through vasodilatation.