Daily University Science News
Since the
beginning of time, middle-aged women have suffered hot flashes,
sweating, heart palpitations, depression and anxiety -- the characteristic
symptoms that mark the end of menstruation and the beginning of
menopause.
But new research
at the University of Michigan Health System may counter the conventional
wisdom that menopause is an unavoidable "rite of passage"
for middle-aged women, and suggests that medical advances may
make it possible to ease its symptoms, delay its onset, or even
"cure" it.
U-M researchers,
led by Nancy Reame, M.S.N, Ph.D., the Rhetaugh Graves Dumas professor
in the U-M School of Nursing, are in their fourth year of a trial
to test the theory that menopause doesn't start in the ovaries,
as is commonly understood, but with a disruption of circadian
rhythms in the brain. Although the study, funded by the National
Institutes of Health's Institute on Aging, is not completed, preliminary
findings are already showing promise.
"If we
can understand the causes of the very early, initial changes that
may be happening in the brain to bring on menopause, we will probably
then have a way of intervening much earlier than at the time of
menopause," Reame says.
She explains
that finding the physiological origins of menopause could have
numerous advantages, such as delaying menopause for women who
want to have children in their 40s and 50s, or easing the effects
of hot flashes and other symptoms.
Researchers
may even be able to use this information to find ways to decrease
women's risks of heart disease, heart attacks and osteoporosis
-- three medical conditions for which women in menopause are more
susceptible. But first, the U-M team and their peers must continue
their research.
For decades,
it has been commonly accepted that menopause starts when a woman
runs out of eggs in her ovaries as she ages.
"The
importance of the loss of eggs over time is that the egg is the
source of estrogen that we need to protect our bones and our heart,"
Reame says. "It's also important in the regulation of the
menstrual cycle. So, as the number of eggs declines with age,
we also gradually lose the estrogen and by the time menopause
comes around, the levels of estrogen are much, much lower than
they are in a young woman."
At birth,
female babies have about 5 million eggs. By about age 35, that
number has declined to about 25,000 eggs. After age 35, egg loss
accelerates.
Recently,
though, there has been a shift in researchers' thinking away from
crediting the loss of eggs for the start of menopause. Reame and
other researchers are now suggesting that changes in a woman's
brain due to aging might be the initial trigger for menopause.
"Obviously,
you can't go in and look at women's brains to see the changes
to the hypothalamus, which is the part of the brain that regulates
the menstrual cycle and ovulation," Reame says. "Instead,
we at U-M are studying a particular brain function that we know
plays an important role in the menstrual cycle regulation, and
that is the production of the hormone GnRH."
In particular,
Reame says she is measuring how the production of GnRH - gonadotropin
releasing hormone -- changes both through a woman's life and throughout
a 24-hour period -- especially during sleep. GnRH is released
from the brain and interacts with the pituitary gland to secrete
hormones in a special rhythm that signals the ovary to stimulate
growth of a new egg each month.
"Because
GnRH is the conductor of the reproductive cycle, any changes in
the brain that start early on could conceivably be the preemptive
cause for this change in ovarian function and perhaps, may be
part of early changes associated with menstrual cycle irregularity,"
Reame says. "We are speculating that in older women there
is a different, or disordered, signal from the brain in terms
of the stimulation of the ovary to accelerate egg loss."
When young
women sleep, the frequency of the release of GnRH decreases significantly,
but the size of the pulses of hormone that come from the brain
are much larger. There's an important slowing-down, but magnifying,
of each message from the brain to the ovaries at night in young
women, Reame says. In older women, the rhythm appears to be altered.
To measure
the exact changes in the levels of hormones in each pulse, researchers
bring study participants to a sleep lab at the U-M General Clinical
Research Center and take blood samples through an IV every 10
minutes around the clock. That allows them to analyze the day
and night differences in GnRH being released by the brain.
In addition
to younger women with regular cycles, older women who are still
having normal menstrual cycles and postmenopausal women were studied
in the same fashion "to see whether the same change in GnRH
levels occurs in the brains of older women," Reame says.
"We're
in our fourth year of our research study right now and, although
still preliminary, we're seeing some exciting results," Reame
says. "We certainly are now able to see some differences
between the young cycling women and the older cycling women in
relation to this sleep entrained change and brain function."
Other findings
have revealed the ovaries produce more hormones than was initially
thought. "Besides estrogen, there are a number of other hormones
produced by the ovaries that we think play an important role in
fine tuning menstrual cycle regularity and maintaining fertility,"
Reame says. "We now know that these fine-tuning hormones
are also lost over time, well before estrogen levels drop."
Reame hopes
that finding the origins of menopause may lead to relief for women
who suffer from its symptoms, and bring hope to women who want
children in mid-life.
"One
in 100 women will undergo menopause before age 40, and that can
be devastating if they are still planning to have more children,"
Reame says. "These women with early menopause may also have
a significant risk of increased cardiovascular disease and heart
attack. The loss of estrogen also carries with it a significant
risk of osteoporosis for these younger women."
Reame's work
and that of other researchers in the field could ultimately lead
to a voluntary absence of menopause. "We may have a cure
for menopause, if we really want to do that," Reame says.
"The
downside to this would be a much higher incidence of breast cancer,"
Reame says. "It's well known that there's a direct correlation
between the length of exposure to estrogen and risk of breast
cancer. The greater the number of menstrual cycles, the higher
the risk."
If you are
between the ages of 20 and 30, or 40 and 50, a non-smoker of average
weight with no sleep problems, and want to see if you're eligible
to participate in the study, check
out this website. - By Valerie Gliem
Facts about
menopause:
· Menopause
is the time in a woman's life after she ceases to menstruate.
· Most
women will experience menopause by age 50, but it can occur earlier
or later, depending on individual hormone patterns. Some of the
signs of menopause include hot flashes, sweating, heart palpitations,
anxiety, and depression. Hormone replacement therapy or other
medications may be taken to ease these symptoms.
· Women
after menopause have a higher risk of heart disease, osteoporosis,
breast cancer and other diseases.
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