TESTOSTERONE Study: Hormone may lower Alzheimer's risk

The field of hormone replacement therapy and the disease is controversial.
MILWAUKEE JOURNAL SENTINEL
MILWAUKEE -- Testosterone, the hormone that has inspired affairs, corporate takeovers and wars, also may help men remember their exploits.
Research published today indicates that men with higher levels of free circulating testosterone are at lower risk for developing Alzheimer's, a finding that follows other studies showing that testosterone can improve performance on memory and other cognitive tests.
The study is added impetus for an anticipated series of hormone replacement therapy trials, this time with men as the test subjects.
Although the science to support its use is far from complete, more men are using testosterone because it makes them feel better or for some other perceived benefit.
An estimated 800,000 middle-age and older men are using testosterone supplements, according to an editorial that accompanied the study in the journal Neurology.
"Is the testosterone hypothesis strong enough to justify long-term intervention?" asked editorial writers Victor Henderson and Eva Hogervorst from the Department of Geriatrics at the University of Arkansas for Medical Sciences. "Perhaps someday it will be."
Hormone replacement therapy and Alzheimer's is a controversial, unsettled field.
Women's study
Last year, the ongoing Women's Health Initiative study found that twice as many women who took combination estrogen and progestin supplements developed dementia than those who did not take the supplements.
However, the effect of estrogen alone still is under study. And some researchers believe that estrogen, just like testosterone, may prove to be beneficial in preventing Alzheimer's.
The new study, which was funded by the National Institutes of Health, is the first prospective study to find an association between low levels of circulating free testosterone and the risk of developing Alzheimer's years down the road.
The study followed a group of 574 men for an average of 19 years.
At various times, their testosterone levels were measured. Researchers also calculated so-called free testosterone, the type that is known to be active in the brain. Much of the testosterone in the blood is bound to a protein that prevents it from crossing through blood vessels and into the brain.
But unbound testosterone can enter the brain, and other research suggests it can suppress levels of beta-amyloid, one of two proteins that accumulate in the brains of people with Alzheimer's.
Testosterone also may enhance the activity of the brain chemical acetylcholine, which is needed for brain cells to communicate.
It also appears that some testosterone is converted to estrogen in the brain, said Susan Resnick, co-author of the study and an investigator with the National Institute on Aging.
"We don't really know ... whether it's estrogen that's having the effect," she said.