Alzheimer News:

Study: Decreased Testosterone Levels Put Aging Men at Risk for Alzheimer's

Decreased levels of testosterone may put aging men at risk for Alzheimer's disease, according to a study by University of Southern California (USC) researchers.

Using brain tissue from 45 deceased males including those with Alzheimer’s and those in the control group who had no clinical history of cognitive impairment, the researchers fond that the brain levels of testosterone were significantly lower in Alzheimer's subjects compared with control subjects. Brain levels of testosterone were also significantly reduced in men with mild neuropathology consistent with early Alzheimer's disease.

"Our findings strongly suggest that normal age-related testosterone depletion is one of the important changes that promote Alzheimer’s disease in men," said study author Christian Pike, an assistant professor at the USC Leonard Davis School of Gerontology. "Understanding how these changes increase vulnerability to the disease is critical not only for elucidating Alzheimer's development, but also for identifying those persons most at risk."

Only within the last few years has the range of impairments - including osteoporosis and the loss of muscle mass, strength and function - linked to decreased testosterone levels become a recognized clinical syndrome called ADAM or androgen deficiency in aging males. Androgens are male sex hormones.

The researchers said the brain is another tissue that experiences age-related testosterone loss and that increased vulnerability to Alzheimer's disease should now be considered a component of ADAM.

"Thus far, our research tells us that testosterone has at least two critical brain functions relevant to Alzheimer's disease," Pike said. "It protects neurons from injury, and it reduces levels of beta-amyloid, the protein widely implicated as a causal factor in the disease."

"We believe that the loss of testosterone with advancing age creates a more hostile neural environment that promotes accumulation of toxic beta-amyloid protein while leaving neurons less able to survive the insult," he added.

Pike and his colleagues are now seeking to determine the mechanism by which testosterone depletion places the brain at increased risk for the mentally debilitating disease. "Advancing age is the most significant risk factor for Alzheimer's disease," Pike said. "We now have to find the age-related changes that combine to promote the disease."

The researchers described their findings in a letter to the editor published in the September 22 issue of the Journal of American Medical Association.

Source: Medical Week staff, week of October 9, 2004