The Truth About Hot Flashes

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The History of Hot Flashes

Q. How on earth did you end up studying hot flashes? A. "About twenty years ago, a graduate student who had read my research on using biofeedback to treat Raynaud's disease [a condition that causes blood vessels to constrict, limiting blood flow] came to me and said, 'You've taken cold women and made them warm. Can we do the opposite?' His mother had breast cancer, so she couldn't take hormone therapy. So this kid got me started."

Q. Was there any other research back then? A. "Not much. Even today, only a handful of scientists in the country are studying hot flashes. Probably the first important paper, which was published over twenty years ago, was by Samuel Yen, an endocrinologist then at UCLA. It showed that seventy percent of hot flashes recorded in the laboratory corresponded with LH pulses [leutinizing hormone, which is produced in the pituitary gland and involved in ovulation and menstruation]. People worked on the theory that LH pulses were the trigger for five to ten years, until another group at UCLA disproved it."

Q. What do you think causes hot flashes? A. "My guess is it's a combination of aging, and estrogen withdrawal affecting hermoregulation in the brain. Estrogen withdrawal is necessary, but not alone responsible, for hot flashes to occur. We do know that norepinephrine levels are higher in the brains of women who have flashes compared to women who don't. Estrogen withdrawal has been linked to elevated brain norepinephrine levels in several animal and a few human studies. "The master temperature control in your body is probably in the hypothalamus, and it's affected by norepinephrine. The hypothalamus is like your living-room thermostat, which has a neutral zone in which neither the air conditioning nor heating system is turned on. It's the same in the body. Everyone has a thermoneutral zone -- the span between the upper threshold, at which sweating occurs, and the lower threshold, at which shivering occurs. In women who don't get flashes, the neutral zone is about .4 degrees centigrade wide, which means they have a lot of play. But in the flashers, it's almost zero -- probably because increased norepinephrine, possibly brought on by reduced estrogen, has narrowed the zone. Hot flashes occur when small elevations in core body temperature cause a rise that's above this small neutral zone."

Continued on page 3:  What Do They Do?


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