Thyroid Hormone May Boost Women's Alzheimer's Risk (HealthDay)

TUESDAY, July 29 (HealthDay News) -- High or low levels of thehormone thyrotropin may be associated with an increased risk ofAlzheimer's disease in women. Thyrotropin affects thyroid gland functionand thyroid hormone levels.

Between 1977 and 1979, researchers at Beth Israel Deaconess MedicalCenter and Harvard Medical School measured thyrotropin levels in 1,864people, average age 71, without cognitive problems. The participants werethen assessed for dementia every two years.

After an average of 12.7 years of follow-up, 209 participants developedAlzheimer's disease. After they adjusted for the other factors, theresearchers found that women with the lowest (less than onemilli-international unit per liter) and highest (more than 2.1milli-international units per liter) levels of thyrotropin had more than atwofold increased risk of Alzheimer's.

No association between thyrotropin levels and Alzheimer's risk wasnoted in men.

"Whether altered thyrotropin levels occur before or after onset ofAlzheimer's disease, the neuropathologic mechanism is unclear," the studyauthors wrote.

Brain changes caused by Alzheimer's disease may cause a decrease in theamount of thyrotropin released or changes in the body's responsiveness tothe hormone, the researchers said. Or, it may be that high or lowthyrotropin levels damage neurons or blood vessels, resulting in cognitiveproblems.

"In conclusion, low and high thyrotropin levels were associated with anincreased risk of incident Alzheimer's disease in women but not in men.These findings should be considered hypothesis-generating and should bevalidated in other populations before clinical conclusions are drawn," theresearchers wrote.

The study was published in the July 28 issue of the journal Archivesof Internal Medicine.

More information

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