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Estrogen therapy may limit stroke damage if started close to, but
not long after reproductive cycles are over, according to a new animal
study. The results were presented Sunday, June 15, at The Endocrine
Society's 90th Annual Meeting in San Francisco. "This study suggests
that estrogen treatment is not toxic per se but that its effects on the
brain depend on the individual's reproductive age when therapy begins,"
said one of the study's authors, Farida Sohrabji, PhD, of Texas A &
M Health Science Center.
In their study in rats, Amutha Selvamani, a post-doctoral associate
and Dr. Sohrabji, found "that estrogen treatment is not beneficial to
the brain once the animal is in an acylic state, but is effective when
given earlier. This acyclic stage in animals shares similarities with
the menopausal stage in women."
Since the Women's Health Initiative study found that long-term
therapy with estrogen or estrogen plus progestin may increase the risk
of heart attack and stroke, many women have found it difficult to
decide whether to take hormone therapy at menopause. Subsequently,
several researchers have speculated that the timing of estrogen
treatment may be important for estrogen's effects. The authors
therefore designed an animal study to determine if estrogen would be
beneficial for females who are going through menopause (perimenopausal)
but not for women who are postmenopausal for many years. Since it is
not possible to measure "risk" in animal studies, the authors measured
severity of stroke injury.
Therefore, they compared groups of female rats: mature adults and
older, "acyclic" rats that no longer had reproductive cycles. The
physiologic status of the older rats resembled that of a postmenopausal
woman, and the other rats' status would be more similar to
perimenopause, according to Sohrabji. After surgically removing the
ovaries of all the rats, the researchers gave them estrogen replacement
therapy (estradiol) for 3 weeks. Then they induced a stroke in all the
animals. A week later, the rats' brains were studied for tissue damage.
The stroke caused much more tissue damage in the acyclic older
females, the authors reported. "Estrogen treatment to this group
actually increased the volume of the brain that was damaged," Sohrabji
said.
In the mature adult rats, however, estrogen therapy apparently
reduced the area of brain damage. After the stroke all rats showed
evidence of sensory and motor damage on behavioral testing, but it was
more severe in the acyclic rats.
"This study supports the idea that there is a narrow window of time
as a woman approaches menopause and immediately afterward where
estrogen therapy may provide neuroprotective benefits," Sohrabji said.
Source: The Endocrine Society
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