Hot flashes happen when your brain’s internal thermostat malfunctions, triggering a sudden wave of heat, flushing, and sweating even though your body temperature hasn’t actually changed. The most common cause by far is shifting hormone levels during perimenopause, which affects roughly 3 in 4 women in their late 40s and early 50s. But hormonal changes aren’t the only explanation. Thyroid problems, certain medications, and other medical conditions can all trigger hot flashes, and they affect men too.
What Happens in Your Brain During a Hot Flash
Your hypothalamus, a small region deep in the brain, acts as your body’s thermostat. It keeps your core temperature within a narrow comfort zone. When estrogen levels drop, a specific group of neurons in the hypothalamus grows larger and becomes overactive. These neurons start sending erratic signals to the brain’s temperature control center, essentially telling your body it’s overheating when it isn’t.
Your body responds the way it would to real overheating: blood vessels near the skin dilate rapidly, your heart rate increases, and you start sweating. This is your body trying to dump heat it doesn’t actually need to lose. The result is that flushed, drenched feeling followed by a chill as your core temperature actually drops from all that unnecessary cooling. A single episode can last anywhere from 30 seconds to several minutes.
Perimenopause: The Most Common Cause
If you’re in your 40s or 50s, fluctuating estrogen is the most likely reason for your hot flashes. They typically begin during perimenopause, the transitional years before menstruation stops entirely. During this time, your ovaries produce estrogen unevenly. Some months levels spike, other months they plummet, and each drop can trigger episodes.
How long hot flashes last varies enormously. Some women deal with them for a few months. Others have them for years, well past their final period. There’s no reliable way to predict which category you’ll fall into, but women who start getting hot flashes earlier in perimenopause tend to experience them for a longer total stretch. Night sweats, the nighttime version of hot flashes, often disrupt sleep and can be the symptom that drives people to seek help.
Thyroid Problems Can Mimic Menopause
An overactive thyroid gland produces excess thyroid hormone, which revs up your metabolism and can make you feel hot all the time. This heat intolerance overlaps with menopausal hot flashes enough to cause real confusion, especially if you’re in the right age range for both.
There are some key differences. Menopausal hot flashes come in distinct waves that start and stop. Thyroid-related heat intolerance tends to be more constant. The biggest clue pointing toward a thyroid problem is unexplained weight loss despite eating more than usual. That pattern is unusual in menopause. A simple blood test measuring thyroid hormone levels can distinguish the two quickly, and it’s worth asking about if your symptoms don’t fit the typical hot flash pattern.
Medications That Trigger Hot Flashes
Several common medications list hot flashes as a side effect. Tamoxifen, widely used in breast cancer treatment, is one of the most well-known offenders. It works by blocking estrogen receptors, which effectively mimics the estrogen withdrawal of menopause in the brain’s temperature center.
Antidepressants, particularly at higher doses, can also cause or worsen hot flashes and excessive sweating. This is especially pronounced with medications that affect both serotonin and norepinephrine, since norepinephrine directly stimulates the body’s heat and stress responses. If your hot flashes started or worsened after beginning a new medication, that timing is worth noting and discussing with whoever prescribed it.
Hot Flashes in Men
Men get hot flashes too, and the mechanism is the same: the hypothalamus loses its hormonal input and overreacts. In men, the relevant hormone is testosterone rather than estrogen. The most common scenario is men undergoing androgen deprivation therapy for prostate cancer. Between 70% and 80% of men on this treatment experience hot flashes, and for those on long-term therapy, the problem can persist for years. One study found over 40% of men still had hot flashes after more than eight years of treatment.
Men who receive androgen deprivation temporarily, such as alongside radiation therapy, usually see their hot flashes resolve within three to four months of stopping treatment as testosterone levels recover. Outside of cancer treatment, low testosterone from other causes can also trigger hot flashes, though this is less common.
Less Common Causes Worth Knowing
Carcinoid syndrome, caused by rare tumors that release excess hormones into the bloodstream, produces flushing that can look similar to hot flashes. The key difference is how the skin looks: carcinoid flushing often causes color changes ranging from pink to purple, and episodes can last much longer, from a few minutes to several hours. This is uncommon, but flushing paired with diarrhea, wheezing, or a racing heart warrants investigation.
Other potential triggers include high stress and anxiety, which activate the same fight-or-flight pathways involved in flushing. Alcohol, spicy foods, and caffeine can provoke episodes in people who are already prone to them. These lifestyle triggers don’t cause hot flashes on their own, but they lower the threshold for an episode when your thermoregulatory system is already sensitized.
How Hot Flashes Are Treated
Hormone therapy remains the most effective treatment for menopausal hot flashes. By replacing some of the estrogen your body has stopped producing, it directly addresses the root cause and calms the overactive neurons in the hypothalamus. For women who can’t or prefer not to take hormones, newer options now exist that target the problem from a different angle.
The FDA approved a non-hormonal medication in 2023 that works by blocking a specific chemical messenger called neurokinin B, the same signal those overactive hypothalamic neurons use to disrupt your thermostat. It’s taken as a daily pill and represents the first treatment designed to interrupt the exact neural circuit responsible for hot flashes rather than replacing hormones broadly. This is particularly relevant for women with a history of breast cancer or blood clots, for whom hormone therapy carries additional risks.
Lifestyle strategies can also help reduce the frequency and severity of episodes. Keeping your environment cool, dressing in layers you can shed quickly, limiting alcohol and spicy food, and maintaining a healthy weight all lower the likelihood of triggering an episode. Regular exercise appears to help some women, though the evidence is mixed on whether it reduces hot flash frequency or simply improves your ability to tolerate them.