Natural estrogens may offer some protection to premenopausal women threatened with severe brain damage during stroke, according to a study led by researchers at Johns Hopkins and the National Institutes of Health.
Results of the study are published in the January issue of the journal Stroke. They show that in female rats, endogenous estrogens, those naturally produced by menstruating females, support blood flow to the brain during stroke and limit brain tissue damage.
"What we have is a possible explanation for the well-documented but poorly understood clinical observation that premenopausal women are at lower risk for stroke damage than men of the same age," says Patricia D. Hurn, Ph.D., senior author of the study and an associate professor of anesthesiology and critical care medicine at Hopkins. "It may also explain the steep rise in stroke incidence in women after menopause."
The researchers created strokes in anesthetized male and female rats by blocking blood flow for two hours through the middle cerebral artery, a brain blood vessel commonly linked to cerebrovascular disease and stroke in humans. Female rats had higher percentages of cerebral blood flow during stroke than males and smaller amounts of damaged brain tissue afterward.
When strokes were created in female rats whose ovaries had been surgically removed, and who therefore had lower levels of natural estrogen, stroke damage was essentially the same as in males. This indicates that female sex steroids, most likely estrogen, protect the brain, according to Hurn.
"A growing body of evidence indicates that estrogen has multiple vascular effects, all of which could contribute to the salvage of brain tissue during episodes of inadequate blood flow," she says.
Ongoing studies suggest that estrogen supplements would have similar effects, she says.
The study's other authors were Nabil J. Alkayed, M.D., Ph.D.; Izumi Harukuni, M.D.; and Richard J. Traystman, Ph.D., of Hopkins; and Alane S. Kimes, Ph.D., and Edythe D. London, Ph.D., of the National Institute on Drug Abuse. The study was supported by three grants from the National Institutes of Health.