Hot Flashes

Sometimes I get asked questions in unusual places. A few months ago at church I was pulled aside and asked if I could write my column on the menopausal malady of 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 entire body. Many women experience flushing of the skin over the involved area, hence they may also be called hot flushes.

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

Hot flashes are caused by a reduced level of estrogen, the hormone that is made primarily by the 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 and she develops “surgical menopause.”

One of estrogen’s biochemical targets in the body is the hypothalamus, a collection of nerve cells found at the base of the brain. One of the jobs of the hypothalamus is to function as the thermostat of the body. It regulates body temperature via the autonomic nervous system. Autonomic nerves cause blood vessels in the skin and elsewhere to either expand (vasodilation) allowing the release of heat from the body, or to constrict (vasoconstriction) which helps to conserve heat.

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

This also explains the problems many women have with night sweats. The level of circulating estrogen in the body is usually 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 poor sleep that is the felt to contribute to irritability that many women describe in 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 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 it is not taken with progesterone. Estrogen has also been shown to increase the risk of cardiovascular disease (heart attack and stroke) if taken for an extended period of time, particularly in women who smoke.

Current science suggests that estrogen replacement is probably safe for about 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 blood clots should not take estrogen. Smoking also increases a woman’s risk of complications. Any woman who decides to take estrogen should take it at the lowest effective dose for the shortest amount of time.

Some herbal preparations may be somewhat 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. Some antidepressant medications can also be helpful. The one that seems to work the best is venlafaxine or Effexor®.

Dr. John Roberts is a member of the Franciscan Physician Network specializing in Family Medicine as well as the Deputy County Health Officer in Montgomery County.