Women who abruptly and prematurely lose estrogen from having their ovaries removed have double the risk of cognitive decline and dementia, according to a new study in the journal Brain.
"This is what the clinical studies indicate and our animal studies looking at the underlying mechanisms back this up," said researcher Darrell Brann. "We wanted to find out why that is occurring. We suspect it's due to the premature loss of estrogen."
In an effort to mimic what occurs in women, Brann looked at rats 10 weeks after removal of their ovaries that were either immediately started on low-dose estrogen therapy, started therapy 10 weeks later, or never given estrogen.
When Brann and his co-researchers caused a stroke-like event in the rodents' hippocampus, a center of learning and memory, they found the rodents treated late or not at all experienced more brain damage. To make matters worse, untreated or late-treated rats also began an abnormal, robust production of Alzheimer's disease-related proteins.
Brann says both problems appear associated with the increased production of free radicals in the brain. In fact, when the researchers blocked the excessive free radical production, heightened stroke sensitivity and brain cell death were reduced.
Interestingly, the findings appear to be gender specific. Brann says removing testes in male rats, didn't affect stroke size or damage.
Although exactly how it works is unknown, estrogen appears to help protect younger females from problems such as stroke and heart attack. Their risks of the maladies increase after menopause to about the same as males. Brann says follow up studies are needed to see if estrogen therapy also reduces sensitivity to the beta amyloid protein associated with Alzheimer's.
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Source: Medical College of Georgia at Georgia Regents University