WASHINGTON - Too much
testosterone can kill brain cells, researchers said on Tuesday in a finding that
may help explain why steroid abuse can cause behavior changes like
aggressiveness and suicidal tendencies.
Tests on brain cells in lab dishes showed that while a little of the male
hormone is good, too much of it causes cells to self-destruct in a process
similar to that seen in brain illnesses such as Alzheimer's.
"Too little testosterone is bad, too much is bad but the right amount is
perfect," said Barbara Ehrlich of Yale University in Connecticut, who led the
study.
Testosterone is key to the development, differentiation and growth of cells
and is produced by both men and women, although men produce about 20 times more
of the hormone.
It can also be abused, and recent scandals have involved athletes who use the
hormone, or steroids that turn into testosterone in the body, for an unfair
advantage.
"Other people have shown that high levels of steroid can cause behavioral
changes," Ehrlich said in a telephone interview.
"We can show that when you have high levels of steroids, you have high
testosterone and that can destroy the nerve cells. We know that when you lose
brain cells you lose function."
Ehrlich's team tried the same thing with the "female" hormone estrogen, just
to be fair.
"We were surprised, but it actually looks like estrogen is neuroprotective.
If anything, there is less cell death in the presence of estrogen," she said.
Writing in the Journal of Biological Chemistry, Ehrlich and colleagues said
their findings meant people should think twice about supplementing with
testosterone, even if it does build muscle mass and aid recovery after exercise.
"These effects of testosterone on neurons will have long term effects on
brain function," they wrote.
"Next time a muscle-bound guy in a sports car cuts you off on the highway,
don't get mad -- just take a deep breath and realize that it might not be his
fault," Ehrlich said in a statement.
The cells die via a process called apoptosis, also known as cell suicide or
programmed cell death.
"Apoptosis is an important thing for the brain -- the brain needs to weed out
some of the cells. But when it happens too frequently, you lose too many cells
and causes problems."
A similar process is seen in Alzheimer's disease, the most common cause of
dementia in the United States, affecting an estimated 4.5 million Americans, and
Huntington's disease, another fatal brain illness.
"Our results suggest that the responses to elevated testosterone can be
compared with these pathophysiological conditions," the researchers wrote.
