Hormonal status affects the reactivity of the cerebral vasculature

We compared the blood velocity and vascular resistance in the central retinal and ophthalmic arteries in healthy nonpregnant, pregnant, and postmenopausal women (before and after estrogen replacement therapy).

Color flow Doppler ultrasonography was used to determine systolic, diastolic, and mean velocity, as well as the resistance index in the central retinal and ophthalmic arteries in 10 nonpregnant women, 10 third-trimester pregnant women, and 10 hypoestrogenic postmenopausal women. The postmenopausal patients were again studied 2 months after starting daily oral therapy with 2 mg of micronized 17 beta-estradiol.

Pregnant women had a significantly (p < 0.05) higher diastolic blood velocity (4.2 +/- 0.8 cm/sec) and a lower resistance index (0.56 +/- 0.05) in the central retinal artery, when compared with nonpregnant women (diastolic velocity 2.8 +/- 0.8 cm/sec, resistance index 0.68 +/- 0.1), and hypoestrogenic postmenopausal women (diastolic velocity 2.6 +/- 0.9 cm/sec, resistance index 0.73 +/- 0.08). Significant differences were not seen in the ophthalmic artery. In the postmenopausal patients estradiol therapy was associated with an increase in diastolic velocity (2.6 +/- 0.9 cm/sec vs 4.1 +/- 1.6 cm/sec) and a decrease in the resistance index (0.73 +/- 0.08 vs 0.66 +/- 0.1) in the central retinal artery but not in the ophthalmic artery.

The blood velocity and vascular resistance in the cerebral microcirculation appear to change according to the phases of a woman's reproductive life. This may be related, in part, to estrogen levels, because estradiol vasodilates small-diameter cerebral vessels in hypoestrogenic postmenopausal women.