Hot flushes (flashes in the USA) and night sweats are a common and mysterious experience of midlife and menopausal women. They are episodic, start suddenly, last a few minutes and make us feel too hot with/without sweating. Night sweats are hot flushes occurring during sleep—they may or may not cause wakening. Although previously hot flushes were thought to be caused by low estrogen levels, in their brain actions, hormonal associations and experiences, they closely resemble an addict's drug withdrawal. CeMCOR attributes hot flushes to "estrogen withdrawal." The key trigger appears to be a dropping estrogen level (from high to normal or normal to low). Stopping estrogen hot flush treatment can make hot flushes worse than before estrogen was started.
How do dropping estrogen levels cause hot flushes? They trigger the release of norepinephrine, a brain stress hormone, as well as a "dog's breakfast" of other brain and stress hormones. Norepinephrine narrows the range of body temperatures in which we feel comfortable (thermoneutral zone); we both get too hot when it is only a little warm and too cold when it is only a little cool.
Hot flushes are worse when we are under stress (not just emotional stress but also being in pain or depressed), when we are overweight (especially in perimenopause), if we have irregular times for eating and sleeping and if we smoke. Hot flush strategies and treatments are effective when they decrease our responses to stressful situations. These successful strategies include regularly exercising, learning and practicing relaxation/meditation/slow, deep yoga-type breathing, eating and (as much as possible) sleeping regularly. Many herbal and alternative therapies improve hot flushes somewhat; the "placebo-response" to anything we believe will help us reduces hot flushes by 20 to 50 percent.
Although estrogen is the classical hot flush therapy, estrogen with progestin is more effective than estrogen alone; progestins alone are as effective as estrogen. Recently CeMCOR proved that natural progesterone is both effective and safe for menopausal hot flushes; there was no rebound increase in hot flushes when progesterone was stopped. CeMCOR is currently doing a Canada-wide study of progesterone for perimenopausal hot flushes (/studies/perimenopausal-hot-flush-study).
Night sweats (/resources/topics/night-sweats) mean hot flushes (or hot flashes) that occur during sleep. Night sweats appear to be many women's first experience of hot flushes. CeMCOR scientists found that night sweats that occurred only intermittently across the cycle were more likely to occur around menstruation for women in very early perimenopause. At the time, these early perimenopausal women had regular cycles and few daytime hot flushes.