Most women
experience hot flashes and night sweats either before or during menopause, but
a significant minority don't have these symptoms. Could our genes be a factor
in determining which women get hot flashes?
Your genes are the blueprint for how your body works.
Genetic variation within a species often results in minor differences in
appearance and health. If these effects are beneficial or tolerable until
reproduction, these genes are passed on down families. In this case, there
seems to be evidence for a genetic susceptibility to menopausal symptoms.
Hot flashes or flushes are the end result of a paucity of
estrogen. Although the mechanism by which this happens is unclear, it is likely
to be related to blood vessels. Sweating, flushing and shivering are all
uncomfortable and familiar symptoms.
A team of UCLA-led researchers may have found a clue in a
first-of-its kind study: gene variants that affect a receptor in the brain that
regulates estrogen release and is present across all ethnicities. It appears
that women who have these variants are more likely to have hot flashes than
women who lack them. The study -- published today in Menopause, the
peer-reviewed journal of The North American Menopause Society -- is a step that
could lead to new treatments to relieve the symptom.
"No previous studies have focused on how variants in
women's genes may be linked with hot flashes, and these results were highly
statistically significant," said Dr. Carolyn Crandall, professor of
medicine in the division of general internal medicine and health services research
at the David Geffen School of Medicine at UCLA, and the study's principal
investigator. "These associations were similar across European-American,
African-American and Hispanic-American women, and they persisted even after we
accounted for other factors that might influence hot flashes."
According to the study, more than 70 percent of women
experience hot flashes and night sweats, which are known as menopausal
vasomotor symptoms. Ethnicity has been linked to an increased risk for frequent
vasomotor symptoms, as have greater body mass index, lower education level,
smoking, anxiety and depression. But genetic links to these symptoms have
remained unclear.
The researchers performed a study that looked at common
genetic variations across the entire human genome to find links between
variations in genes and observable traits -- in this case, hot flashes and
night sweats. They examined data from 17,695 postmenopausal women ages 50 to 79
years who participated in the Women's Health Initiative and who provided DNA
samples and information about whether they had experienced hot flashes or night
sweats. The researchers examined more than 11 million gene variants, called
single-nucleotide polymorphisms, sampled across the entire genome.
They found that 14 of the variants were associated with
experiencing hot flashes. All of them were located on chromosome 4.
Specifically, the gene variants are located in the part of chromosome 4 that
encodes the tachykinin receptor 3. This receptor is located in the brain, where
it interacts with nerve fibers that regulate estrogen hormone release. For
example, women with mutations in the receptor 3 gene are infertile. This is the
first human study linking tachykinin receptor 3 gene variants with hot flashes.
Crandall noted that the researchers cannot determine how
environmental factors might have influenced the results. Also, they may have
been unable to detect other, rare gene variants that could also affect hot
flashes. Because this is the first report of its kind in humans, the results
should be confirmed in future studies that would help scientists better
understand exactly how they may affect hot flashes.
"If we can better identify what genetic variants are
associated with hot flashes, this could lead to novel treatments to relieve
them," Crandall said.
JoAnn Manson, chief of the division of preventive
medicine at Brigham and Women's Hospital, agreed: "This (receptor) may in
the future may become a drug target for treatments."
The current treatment for women experiencing severe
flashes and sweats is estrogen therapy, which aims to increase their tolerance
of temperature changes. But this comes with risks, mainly in older women going
through menopause, as excess levels of the hormone have been associated with an
increased risk of blood clots, stroke and breast cancer.
"Right now, for youngish women ages 55 or 50,
estrogen is generally a very effective treatment, (but) as you get older,
beyond 60, the risk starts to go up," Johnson said. "This new
information gives scientists a clue as to what might someday be a safe,
effective way to treat hot flashes for some women."
Safety and a reduced risk are the crucial points when
developing new forms of treatment.
"A treatment free of risk would be a tremendous
advance in women's health," Manson said. "We don't know if this
(research) will yield therapies, but it's a promising start."
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