Study: Reducing Testosterone Level May Up Risk of Alzheimer's

When the testosterone level of men undergoing prostate cancer treatment goes down, levels of amyloid -- the protein implicated in Alzheimer's disease -- go up, possibly putting the these patients at increased risk for Alzheimer's disease, according to a new study.

Researchers from New York University reported at the American Neurological Association annual meeting on their study of six men undergoing prostate cancer treatment.

Dr. Sam Gandy said that "in each of six men, when testosterone levels were suppressed, plasma amyloid levels roughly doubled over the six months' duration of the study." Previous research has shown that brain functions begin to deteriorate if amyloid levels get too high.

"We believe that this phenomenon may explain why Alzheimer's disease occurs in late life," said Dr. Sam Gandy, co-author of the study. "People with a genetic predisposition to Alzheimer's may have borderline amyloid levels until menopause or the male equivalent, andropause, reduces gonadal hormone secretion. Brain amyloid levels may then rise enough to cause amyloid accumulation to begin."

Prior studies have shown that hormone replacement therapy in postmenopausal women may cut their risk of developing Alzheimer's by 50 percent, leading researchers to speculate that gonadal hormones such as estrogen and testosterone may help to break down amyloid.

A large, ten-year study is underway testing the effectiveness of hormone replacement therapy in the prevention of Alzheimer's disease. "If hormones are proven to be effective in this trial, then prevention of Alzheimer's disease may become an indication for hormone replacement therapy in both men and women," said Gandy.

Other sources: American Neurological Association