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Hot flashes: Studies explore the role of genes, obesity and alcohol
Diana Yates,
Life Sciences Editor
217-333-5802; diya@illinois.edu
|
Released
4/24/2007
CHAMPAIGN, Ill. —
Many women in the menopausal transition experience hot flashes: unpredictable,
sometimes disruptive, periods of intense heat in the upper torso, neck
and face. Although generations of physicians have prescribed hormones
to reduce these symptoms, very little research has focused on the underlying
causes of hot flashes.
Three new studies explore the role of genes, obesity and alcohol consumption
in contributing to – or lessening – the intensity and frequency
of hot flashes in midlife women. These studies are part of a five-year
research effort led by University of Illinois veterinary
biosciences professor Jodi Flaws and colleagues at the University
of Maryland, Mercy Medical Center in Baltimore and the School of Medicine
at Johns Hopkins University.
Physicians have long noted that some factors, such as smoking, increase
the likelihood that a woman will experience more – or more intense
– hot flashes than other women. Race also appears to play a role,
with African American women at higher risk than others. But the mechanisms
that cause some women to suffer from severe (frequent and intense) hot
flashes have remained a mystery.
“Even though more than 40 million women experience hot flashes
each year,” the authors wrote in their paper published in Maturitas,
“little is known about the factors that predispose women to hot
flashes.”
To examine whether genetics might play a role in hot flashes, Flaws
and her colleagues conducted a cross-sectional study involving 639 women
aged 45 to 54. The researchers looked at individual differences in the
genes that code for various hormones. An earlier study by the same team
had found that one of these genetic polymorphisms, in an estrogen metabolizing
enzyme, cytochrome P450 1B1, was more common in women who reported higher-than-average
frequency, intensity and duration of hot flashes.
The new study tied the same genetic polymorphism to lower levels of
an androgen known as DHEA-S, and to lower progesterone levels.
These are the first studies to find evidence of a genetic basis for
hot flashes, and the first to look at genetic polymorphisms associated
with hormone levels in healthy women with and without hot flashes.
The progesterone finding is of particular interest, said Flaws, because
the medical community has focused almost exclusively on the role of
low estrogen levels in bringing on hot flashes. Hormone replacement
therapy, which is sometimes offered to women to alleviate hot flashes
or other symptoms of the menopausal transition, may include one or more
estrogens alone or in combination with progesterone or an analogue,
progestin.
“We think there should be more studies looking at the role of
progesterone in causing hot flashes,” Flaws said.
The research team identified a second polymorphism, in a gene encoding
an enzyme, 3-beta-hydroxysteroid dehydrogenase, which also is associated
with an increase in hot flashes.
“People typically didn’t think of hot flashes as having
a genetic component,” Flaws said. “Now we have some evidence
that there is at least in part some genetics behind it.”
In another paper, published in the journal Climacteric, the researchers
used the same data to analyze the link between obesity and hot flashes.
They had shown in an earlier study that obesity is associated with more
frequent and intense hot flashes in midlife women. They now wanted to
see what might be causing this effect: Did the higher incidence of hot
flashes in obese women correlate with varying levels of specific hormones
or other factors?
When looking at blood levels of specific hormones and related enzymes,
the researchers found a significant link between obesity and hormone
levels. Higher body mass index (BMI) was significantly correlated with
higher testosterone and lower total estradiol, estrone, progesterone
and sex hormone binding globulin (SHBG) in midlife women.
The researchers were surprised by the findings related to estrogen,
because adipose tissue produces and stores estradiol, the major estrogen
in humans. Most people had assumed that obese women would have higher
circulating estrogen levels because of this, Flaws said. That assumption
turned out to be incorrect, at least for women in midlife.
“It could be that estrogen levels are higher in the fat, but not
circulating in the blood,” she said. “It’s the blood
that gets to the brain and to the thermoregulatory centers that govern
hot flashes.”
A third analysis, published in the journal Fertility and Sterility,
examined the influence of alcohol consumption on hot flashes in midlife
women.
This study attempted to explain an earlier finding that moderate alcohol
consumption (up to three drinks per month) actually reduced the severity
of hot flashes by 25 percent. This effect vanished in women who consumed
more than three drinks per month.
Because alcohol consumption is known to affect metabolism in some animals,
the team thought that light drinking might alter sex steroid hormone
levels in midlife women. But their analysis failed to turn up any significant
hormonal differences between the alcohol users and the women who never
used alcohol.
“We don’t know why (moderate alcohol consumption) is reducing
the risk of hot flashes, other than it doesn’t seem to be doing
so by changing hormone levels,” Flaws said.
Together, these studies point to some risk factors for hot flashes that
women can change and others that cannot be changed, Flaws said.
“Body mass index, alcohol use and smoking are three things that
can change,” she said. “So probably if women quit smoking,
and they lose weight, it will reduce their risk. If they (engage in)
light drinking, that might also reduce the risk of hot flashes. And
then there’s the genetic piece, which we can’t change.”
Editor’s note: To reach Jodi Flaws, call 217-333-7933; e-mail: jflaws@illinois.edu.
