Cerebral Blood Flow in the Internal Carotid Artery Throughout the Menstrual Cycle in Young, Healthy Women

Background Previous reports suggest female sex hormones may affect cerebral blood flow and cerebral flow velocity in women. The purpose of this study was to examine whether changes in cerebral blood flow occur throughout the menstrual cycle phases that are associated with fluctuations in sex hormones in young, healthy women. Methods A subset of eight female participants (mean age 25 yrs) from our previously published study (Favre & Serrador, 2019) underwent one minute of supine steady‐state cerebral blood flow measurements in the internal carotid artery. Women were studied at three different time points across the menstrual cycle: the early‐follicular (EF) phase associated with low levels of estrogen and progesterone, the late‐follicular (LF) phase associated with high levels of estrogen and low levels of progesterone, and the mid‐luteal (ML) phase associated with high levels of both estrogen and progesterone. Cerebral blood flow in the internal carotid artery was measured using duplex ultrasonography. Beat‐by‐beat blood pressure, end‐tidal CO 2 , ECG, and middle cerebral flow velocity (MCAv) using transcranial Doppler ultrasonography were also obtained. Results There were no statistically significant changes ( P =0.269) in internal carotid blood flow across the menstrual cycle phases (EF=203.9±42.2, LF=227.0±53.7, ML=203.2±47.8 ml/min). When examined as a percent of flow from the early follicular phase, there were also no significant changes ( P =0.207) across the menstrual cycle (EF=100.0±0.0, LF=111.6±14.5, ML=100.8±17.0 %). Additionally, there were no significant changes ( P =0.488) in MCAv (EF=84.7±19.9, LF=89.5±21.2, ML=87.9±24.1 cm/s). End‐tidal CO 2 significantly decreased ( P =0.025) during the mid‐luteal phase compared to the late follicular phase (EF=38.0±3.0, LF=39.3±2.8, ML=37.0±3.1 mmHg). There were no significant changes ( P =0.174) in internal carotid velocity (EF=41.5±7.0, LF=44.8±7.7, ML=40.1±9.2 cm/s) or internal carotid diameter ( P =0.327) across the menstrual cycle phases (EF=0.45±0.02, LF=0.46±0.03, ML=0.46±0.01 cm). Conclusion Although we did not observe statistically significant changes in internal carotid blood flow across the menstrual cycle phases, we recognize that women demonstrated a 11% increase in flow during the late follicular phase, corresponding to a large effect size (Partial Eta Squared= 0.201). Because of our small sample size, we cannot rule out the possibility that the fluctuations in female sex hormones affect cerebral blood flow. Additionally, it is possible that the decreased end‐tidal CO 2 in the mid‐luteal phase hid an underlying increase in cerebral blood flow. However, a larger sample of women is needed to conclude whether cerebral blood flow is affected throughout the menstrual cycle phases. Support or Funding Information This work was supported by the Pharmacology, Physiology and Neuroscience Department at Rutgers Biomedical and Health Sciences.