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Estrogen Therapy Helps Or Hurts The Brain Depending On Reproductive Status, Animal Study Suggests

Date:
June 16, 2008
Source:
The Endocrine Society
Summary:
Estrogen therapy may limit stroke damage if started close to, but not long after reproductive cycles are over, according to a new animal study.
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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 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.

The National Institute on Aging funded this study.


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The above post is reprinted from materials provided by The Endocrine Society. Note: Materials may be edited for content and length.


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The Endocrine Society. "Estrogen Therapy Helps Or Hurts The Brain Depending On Reproductive Status, Animal Study Suggests." ScienceDaily. ScienceDaily, 16 June 2008. <www.sciencedaily.com/releases/2008/06/080615142301.htm>.
The Endocrine Society. (2008, June 16). Estrogen Therapy Helps Or Hurts The Brain Depending On Reproductive Status, Animal Study Suggests. ScienceDaily. Retrieved September 1, 2015 from www.sciencedaily.com/releases/2008/06/080615142301.htm
The Endocrine Society. "Estrogen Therapy Helps Or Hurts The Brain Depending On Reproductive Status, Animal Study Suggests." ScienceDaily. www.sciencedaily.com/releases/2008/06/080615142301.htm (accessed September 1, 2015).

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