Testosterone levels linked to Alzheimer’s

Low levels of testosterone in the bloodstream could indicate that a man is at increased risk of developing Alzheimer’s disease.

Scientists have long thought that estrogen protects cognitive function in women and wanted to see if testosterone might have a similar effect in men, either reducing the incidence of Alzheimer’s or delaying its onset. Researchers at the National Institute on Aging focused on what’s called free, or unbound, testosterone, which is the only form of testosterone that circulates not only in the bloodstream but also in the brain. As with other forms of testosterone, levels decline with age.

In reviewing records of 574 participants in the Baltimore Longitudinal Study of Aging, the researchers, led by Dr. Susan M. Resnick, found that men who developed Alzheimer’s had lower concentrations of free testosterone years before diagnosis.

Because the finding, published in Tuesday’s issue of the journal Neurology, is so new, the researchers are far from knowing whether testosterone therapy could help prevent Alzheimer’s. Such therapy is controversial because of testosterone’s potential to promote prostate cancer.

-- Jane E. Allen