Alzheimer ’s Disease Protected Against by Estrogen

Alzheimer's Disease, Estrogen

More than a decade’s worth of research indicates that estrogen may play an important role in protecting aging persons from developing Alzheimer’s disease. Given the evidence, some researchers are already seeking to apply the protective properties of estrogen towards developing treatment therapies for Alzheimer’s disease.

Estrogen is a hormone that is intimately involved with the female reproductive system. Estrogen is found in both women and men (though to a far lesser extent in men). During puberty estrogen is responsible for triggering the development of the primary and secondary female sexual characteristics. Throughout a woman’s sexually mature life, her menstrual cycle is regulated in part by estrogen.

However estrogen also serves a wide variety of other, non-reproductive functions as well. Estrogens act as important regulators for determining the rate at which sugars and fats are metabolized within the body. They also aid in the maintenance of skeletal homeostasis, and have a great influence on the cardiovascular and nervous systems.

In addition, new evidence also indicates that there is a difference between estrogen that circulates widely throughout the body and estrogen that is synthesized and localized within the brain. The brain can create its own estrogen out of cholesterol. This estrogen is subsequently retained in the brain where it influences memory, learning, mood, and neuro-developmental processes.

Understanding that estrogen affects cognitive function led researchers to explore how the hormone may protect elderly patients from developing Alzheimer’s disease. Alzheimer’s disease is the leading cause of dementia in the elderly, and in particular women are at a higher risk of developing the disease. Women are also known to typically have a faster disease progression. Researchers speculate that this may be because after menopause women experience a precipitous decrease in their levels of estrogen. While men do not have as much estrogen to begin with, their estrogen levels remain relatively stable compared to women. The drop in estrogen levels is associated with a decreased neuroplasticity.

This evidence is compelling enough to have already caused some researchers to look into developing estrogen-based treatment therapies for patients suffering from Alzheimer’s disease. The Kronos Early Estrogen Prevention Study (KEEPS) is currently exploring correlations between levels of cerebral estrogen and cognitive function. In addition the Early versus Late Intervention Trial with Estradiol (ELITE) research groups are conducting similar work in collaboration with the University of Southern California. Such therapies may explore ways to maintain natural estrogen levels in post-menopausal women or explore different synthetics that mimic natural estrogen.

Though still far away from developing a widely-used therapy, the initial results of these estrogen supplementation therapies look promising. Preliminary studies with transgenic mice show and estrogen receptor modulators show a significant degree of efficacy in attempting to control the Alzheimer’s disease progression. In addition, studies with humans have shown that thus far these therapies are safe for further testing with elderly patients.

The protective action that estrogen takes against Alzheimer’s disease is just one part of a growing body of evidence that suggest to some researchers that estrogen is much more than just a sex hormone. Estrogen therapies are also being explored in other areas as well.

By Sarah Takushi

Sources

Molecular and Cellular Endocrinology

Hormones and Behavior

Epidemiological Reviews

KEEPS Publications

Harvard Medical School

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