The effect of HRT on cerebral haemodynamics and cerebral vasomotor reactivity in post-menopausal women.

BACKGROUND Cerebral vasomotor reactivity (CVR) is an index of cerebrovascular dilatory capacity which can readily be assessed using trans-cranial Doppler ultrasound. Impaired CVR is associated with elevated risk of stroke. We performed a randomized, double-blind placebo-controlled trial to investigate the effect of two HRT preparations upon CVR. METHODS We examined middle cerebral artery mean flow velocity (MFV), internal carotid artery pulsatility index (PI) and CVR to an i.v. acetazolamide bolus using ultrasound in three groups of post-menopausal women randomized to oral estradiol 1 mg+norethisterone 0.5 mg (group N), estradiol 1 mg+dydrogesterone 5 mg (group D) or placebo (group P). The MFV, PI and CVR were measured before and after 3 months treatment. RESULTS Thirty-eight post-menopausal women were recruited (N=12, D=14, P=12); mean (SE) age was 56.7 (4) years. Neither HRT preparation affected CVR [% (SE) change from baseline N +4.2 (11); D +3.8 (5.5); P +4.0 (3.8); all comparisons P = NS]. PI was significantly reduced in recipients of dydrogesterone [% (SE) change from baseline D -5.4% (4.6); N +12.3 (6.9); P +11.6 (6.9). P=0.025]. Middle cerebral artery velocity was significantly increased following dydrogesterone treatment compared with placebo [% (SE) change from baseline D +6.8 (3.4) N +3.9 (4.2) P -4.6% (3.4) P=0.03 for D versus P]. CONCLUSION HRT did not alter CVR. The reduced PI and increased MFV suggest HRT-induced intracranial vasodilatation, which is more apparent in dydrogesterone recipients. Differences may exist between progestogens with regard to changes in intracranial haemodynamics.