BOSTON, MA — Hot flashes are well known to most menopausal women—and to many who are in perimenopause, the transition to menopause. Hot flashes tend to come on suddenly and last from one to five minutes; they can range in severity from fleeting warmth to a feeling of being on fire. The August issue of Harvard Women's Health Watch explores why women experience this symptom differently, and why some don't experience it at all.
Although the physiology of hot flashes has been studied for more than 30 years, no one is completely sure why or how they occur. One possible explanation has to do with an individual's tolerance for temperature changes. One line of research shows that women who have hot flashes have a lower tolerance for changes in the body's core (innermost) temperature than women who don't have hot flashes.
Normally, the body tries to maintain its core temperature within a comfortable "thermoneutral zone." When core body temperature crosses the upper threshold of this zone, sweating occurs; when it drops below the lower threshold, shivering results. Women who have hot flashes have a thermoneutral zone that's so narrow, even the tiniest changes in core body temperature can trigger sweating (or chills). These symptoms are generally absent in women with a wider thermoneutral zone, explains the Harvard Women's Health Watch.
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