Influence of 17-beta-estradiol on cerebrovascular impedance during menstrual cycle in women.

Numerous experimental studies showed that estrogen alters diameters of cerebral arteries by modifying production of vasoactive substances. In this study, we address a question whether increased concentration of 17-beta-estradiol (E2) during a typical menstrual cycle of young, healthy women influences cerebrovascular impedance, as measured with Doppler pulsatility index (PI) in the common (CCA), internal (ICA), and external (ECA) carotid arteries using duplex Doppler sonography. PI was determined and correlated with plasma E2 concentration in 14 women (ages 23-25) throughout their menstrual cycle. The concentration of E2 increased in the follicular phase of the cycle and reached a peak of 140-300 pg/ml on days 13 and 14, whereas concentration of progesterone remained low (<1 ng/ml). Along with an increase in E2 concentration, the ICA PI decreased from its initial level on average by 11% on day 13 and by 7% on day 14 (r=-0.41, P<0.05). In contrast, the value of the ECA PI showed an increasing trend during the peak of E2 concentration. There were no significant changes in the CCA PI as well as in the systolic blood pressure, heart rate, hematocrit, and hemoglobin concentration during the menstrual cycle. Cerebral vascular impedance in young women is modulated by concentration of E2 throughout the menstrual cycle. The decrease in the ICA PI during the late follicular phase seems to be attributed to a decrease in cerebrovascular resistance.