Medical scientists are close to identifying the key causes of hot flashes that strike menopausal women — reporting significant progress toward a potential cure for the uncomfortable surges of heat and sweating millions of women experience in middle age and later.

Researchers at the University of Arizona College of Medicine in Tucson have determined a region of the brain contains a chemical “on-off switch” that can trigger hot flashes when estrogen levels drop, as they do with age.

The findings, published in the Proceedings of the National Academy of Sciences, are based on studies of laboratory rats. But researchers said they expect the biochemical trigger for hot flashes is the same in women.
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Lead researcher Dr. Naomi Rance, a professor in the department of pathology at the UA College of Medicine, said the researchers have identified a group of brain cells known as KNDy neurons that act as a control switch for hot flashes. The KNDy neurons — pronounced "candy" — are located in the hypothalamus, a portion of the brain that controls vital functions and interactions between the central nervous system and hormone signals.
Dr. Rance’s team used a toxin to deactivate KNDy neurons in rats and found their skin temperature subsequently dropped — suggesting the neurons control the widening of the blood vessels known as vasodilation that lead to hot flashes by increasing blood flow to the skin.
"The hallmark of hot flushes is vasodilation," explained Dr. Rance. "When you flush, your skin gets hot and you can see the redness of the skin. It is an attempt of the body to get rid of heat, just like sweating. Except that if you were to measure core temperature at that point, you would find it is not even elevated."
She added that the results are a key step toward developing therapies that may help individuals affected by hot flashes. Current treatment includes estrogen replacement therapy, which is controversial because of potential health risks, including higher odds of certain cancers. Another option is selective serotonin reuptake inhibitors (SSRIs), which are traditionally used to treat depression.
"For some people it's not too bad, but it can be very severe in other individuals; they lose sleep et cetera,” Dr. Rance noted. “So the question I have been asking myself is, 'How come we haven't figured this out?' "
The study was funded, in part, by the National Institutes of Health.
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