Background. Epidemiologic studies suggest that estrogen replacement therapy
(ERT) is protective against vascular disease. ERT confers this benefit by
lowering lipid levels and improving arterial Function. However, its effect
on the microvasculature in vivo is unknown. Thus the purposes of this study
were to evaluate effect of estrogen status on the hyperemic response of th
e microvasculature in vivo in postmenopausal women and to compare the hyper
emic response of the microvasculature in postmenopausal women taking ERT wi
th that of premenopausal women.
Methods. We measured forearm microvasculature flow velocity by using a lase
r Doppler in a cross section of 64 healthy premenopausal and postmenopausal
women 23 to 72 years old. Microvasculature blood flow velocity was measure
d at baseline, throughout 2 minutes of ischemia, and immediately after the
ischemic period was terminated (i.e.. during the peak hyperemic response).
Results. The peak of the hyperemic flow velocity (PHFV) in the postmenopaus
al women who were taking long-term RT at usual doses was greater than that
of postmenopausal women who were not currently taking ERT (p < .0001). More
over. the PHFV of postmenopausal women taking ERT was similar to that of pr
emenopausal women, Multivariate regression analysis showed estrogen status
and baseline flow velocity to be independent predictors of PHFV.
Conclusions. Current, long-term ERT at usual replacement doses is associate
d with improved microvascular responses in postmenopausal women, which may
explain some of its beneficial vascular effects.