Sometimes I get asked questions in the most unusual places. A few months ago at church I was pulled aside and asked if I could write my column on that scourge of women - hot flashes.

Hot flashes are usually described as a feeling of intense heat, usually with sweating and a rapid heartbeat. They can last a few minutes up to a half hour or so. The feeling usually starts on the face or upper chest but can also be on the neck and even spread over the whole body. Many women experience flushing of the skin over the involved area, hence the alternate name "hot flushes."

Interestingly, some women never experience them. There is no hard and fast rule when or if hot flashes will develop. Some women are "lucky" enough to have them for only a few months while others (up to 45 percent) may suffer for five or even ten years. Some may have infrequent episodes while others may have them numerous times a day.

So, you ask, what causes hot flashes? The primary culprit is a woman's lack of the hormone estrogen that is made by her ovaries. The production of estrogen gradually tapers off as a woman ages. If a woman has undergone surgical removal of the ovaries, the estrogen level drops rapidly.

One of estrogen's effects in the body is on the hypothalamus found at the base of the brain. The hypothalamus can be thought of as the thermostat of the body. It regulates body temperature via the autonomic nervous system. These nerves cause blood vessels in the skin and elsewhere to dilate (vasodilation) helping to release heat from the body and to constrict (vasoconstriction) helping to conserve heat.

Blood levels of estrogen are in constant flux in and around menopause. This, in turn, gives the hypothalamus confusing signals resulting in vasodilation at inappropriate times. This increases blood flow to the skin resulting in the warmth, sweating and flushing typical of a hot flash.

This also explains the problems many women have with night sweats. The level of estrogen in the body is typically lowest during sleep. This, on top of the already low level of estrogen in menopause, triggers the hypothalamus to cause vasodilation. Hot flashes at night can result in chronic poor sleep as well as the infamous irritability of menopause. Lack of sleep can also cause cognitive difficulties with concentration and memory.

The most effective treatment for hot flashes is replacement of estrogen. Taking estrogen after menopause is probably associated with a slight increased risk of breast cancer (depending on length of exposure) and does increase the risk for cancer of the uterus if taken alone. Estrogen has also been shown to increase the risk of cardiovascular disease (heart attack and stroke) if taken for an extended period of time, and particularly in women who smoke.

Current knowledge suggests that estrogen replacement is probably safe for the first five years after menopause in low risk women who have intolerable hot flashes. Women who have a history of breast cancer, undiagnosed vaginal bleeding after menopause, severe liver disease or a history of severe blood clots should not take estrogen. Any woman who decides to take estrogen should take it at the lowest effective dose for the shortest duration.

Some herbal preparations may be helpful with hot flashes. The most popular one is black cohosh, a member of the buttercup family. There have not been many well-designed studies to assess its effectiveness, but anecdotal evidence seems to indicate is may be helpful and probably not harmful. If a woman is interested in using it, I usually recommend Remifemin® which is a standardized preparation. Recall that herbs are not regulated by the FDA. Antidepressants can also be helpful. The one that seems to be the most helpful is venlaxifine or Effexor®.

Dr. John Roberts is a family physician. He is also one of the owners of The Paper of Montgomery County. Send him your question today by e-mail at the