- LOS ANGELES (AP) -- Sex hormones can influence brain development in the young,
memory in the old and may explain why young men tend to develop neurological
problems like autism and dyslexia while older women suffer from depression
and anxiety, scientists say.
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- "We are recognizing with some surprise
the extent to which the brain responds" to sex steroids, said Douglas
Meinecke of the National Institute of Mental Health in Washington. "These
hormones -- testosterone, progesterone and estrogen -- have profound effects
on the brain and the brain is profoundly responsive."
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- Meinecke discussed the role of sex hormones
in development and aging Monday at the Society for Neuroscience annual
meeting.
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- Researchers hope the hormones can be
used to fend off the ravages of aging and disease. Already, estrogen replacement
therapy has been observed to protect older women against Alzheimer's disease.
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- Nancy Forger, a psychologist at the University
of Massachusetts, said she's found that sex hormones can prevent cell death.
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- Men have more motor neurons in their
spinal cords that govern muscles attached to the penis, she found. The
neurons are found both in men and women before birth; however, in the absence
of male hormones, the neurons degenerate in females.
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- Forger is trying to learn how male hormones
save these cells and understand the role of proteins that regulate growth
and survival of neurons.
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- Margaret McCarthy, a physiologist at
the University of Maryland School of Medicine, suggested that early exposure
to male hormones can create permanent brain changes.
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- Testosterone levels in rats are as high
in development as they're going to be in adulthood, she said. Giving a
female rat testosterone creates "a male brain never to be switched
back."
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- Similarly, if testosterone-producing
organs are removed from the male rat, he ends up with a "female brain,"
she said.
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- Only male reproductive organs produce
sex hormones during development, she said. Female sex organs, which produce
estrogen, are inactive until later.
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- "As far as we know, it is also true
for humans," McCarthy said.
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- Asked about male and female brain differences,
she noted that boys suffer from more neurological disorders than girls.
They're more likely to have schizophrenia, autism and dyslexia, while girls
are more likely to suffer neurological illnesses later in life such as
major depression, anxiety disorders, panic disorders or eating disorders.
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- "This hormonal difference early
in life may set up a situation that more easily goes awry and explains
why boys are more susceptible at an early age," she said.
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- John Morrison, a neurobiology professor
at Mount Sinai Medical School in New York, said his studies of estrogen's
effects on a brain region called the hippocampus may shed light on aging.
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- He has that found the number of receptors
on hippocampal cells fluctuates, depending on how much estrogen is present.
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- "The hippocampus mediates memory
and loss of memory is one of the key events to aging," he said.
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