Hot flashes do not always come from menopause. The causes range from an overactive thyroid to medication, anemia and swinging blood sugar, and they all produce the same sudden wave of heat.
In a study of 795 older primary care patients, 8 percent were bothered by hot flashes and 18 percent by at least one type of sweating episode (Mold, 2004). Far from all of them were going through menopause.
What strikes me: almost every Dutch article about hot flashes assumes menopause is the explanation. For the largest group that is fair. But it is also why a 32-year-old with an overactive thyroid sometimes loses half a year before anyone checks her TSH.
Can you have hot flashes without being in menopause?
Yes, you can. A hot flash starts in the temperature control centre in your brain, not in your ovaries. Anything that irritates that system can trigger a wave of heat: thyroid hormone, adrenaline, fever, alcohol or certain medicines. Falling estrogen is the best known route, but it is one of several.
Research into the mechanism shows that the temperature zone in which your body feels comfortable narrows during hot flashes (Freedman, 2014). A small rise in body temperature is then enough to switch on sweating and blood vessel widening.
Thuisarts.nl, the Dutch GP information service, describes hot flashes mainly in the context of menopause, which fits most women over 45. If you are well below that age, looking further makes sense.
8 causes of hot flashes besides menopause
Below are eight causes that can produce the same complaint. For five of them a blood test can give direction. You recognise the other three mainly by the pattern and the moment the heat arrives.
1. A thyroid working too fast
In hyperthyroidism your thyroid produces too much hormone. Heat intolerance, sweating, palpitations, weight loss and restlessness belong to that picture (De Leo, 2016). Of all the causes on this list, this one is mistaken for menopause most often.
Two values give the most direction: TSH and free T4. With an overactive thyroid, TSH is usually low while free T4 rises. Read more in overactive thyroid: symptoms, causes and testing.
2. Stress, anxiety and panic
Under tension your body releases adrenaline. Your heart rate climbs, your blood vessels widen and you feel warm. During a panic attack this can happen within seconds, often with palpitations and a tight chest alongside it.
Long-term stress works more slowly, through cortisol. A single measurement says little there, the pattern across the day says more. We wrote earlier about high cortisol and chronic stress.
3. Medicines that trigger heat
Quite a few medicines list hot flashes or flushing as a side effect. Tamoxifen is the best known example. Some antidepressants, opioids, calcium channel blockers and osteoporosis drugs can do it too.
The Farmacotherapeutisch Kompas, the Dutch prescribing reference, lists the reported side effects per drug. If your hot flashes started within a few weeks of a new prescription, that is a clue worth raising with your GP or pharmacist. Never stop a prescribed medicine on your own.
4. Early menopause before 40
In roughly 1 in 100 women the ovaries stop working before the age of 40 (Nelson, 2009). Technically that is menopause, but so early that almost nobody thinks of it.
FSH and estradiol give direction here: FSH rises while estradiol falls. If you recognise more signals, read early menopause: 11 symptoms you can recognise.
5. Anemia and iron deficiency
With anemia your blood carries less oxygen. Your heart compensates by pumping faster. That can feel like heat, dizziness and sweating during light exertion.
Hemoglobin shows anemia, ferritin shows your iron stores. The two can diverge: your stores can already be low while your hemoglobin still looks normal. More on that in anemia in women.
6. Swinging blood sugar
A rapid drop in blood sugar switches on the same stress response: adrenaline, shaking, sweating and heat. Many women notice this a few hours after a carbohydrate-heavy meal, or after a skipped lunch.
Fasting glucose and HbA1c give an impression of how your blood sugar behaves on average. If the heat keeps arriving around the same point after eating, that is the pattern to write down.
7. Alcohol, caffeine and spicy food
Alcohol widens your blood vessels, which makes your skin feel warm and can turn it red. Capsaicin from peppers irritates receptors your brain reads as heat. Caffeine adds to it through adrenaline.
This is the easiest group to test yourself. If the heat arrives within twenty minutes of a glass of wine or a curry, you have probably found your answer. With these causes it often stays at warmth without much sweating.
8. Fever, infections and rarer conditions
Fever from an infection brings heat and night sweats. Rarer are conditions such as carcinoid syndrome or certain lymphomas, where night sweats come together with weight loss or persistent fever.
A sober note belongs here. A systematic review of night sweats in primary care found that the classic serious causes were rarely the explanation, and that life expectancy in these patients appeared normal (Mold, 2012). Night sweats on their own are not an alarm signal.
Which blood value belongs to which cause?
This table sets the eight causes alongside what could be measured. Treat it as a thinking aid to organise your complaints, not as a diagnosis. Which values make sense in your situation is something your GP decides with you.
Take two women of 41 with the same complaint: eight hot flashes a day. In the first, TSH is 2.1 mU/l and FSH 38 U/l. That fits menopause. In the second, TSH is 0.05 mU/l and FSH 5 U/l. That points more towards a thyroid working too fast. Same complaint, different track.
| Possible cause | What can be measured | What may fit the picture |
|---|---|---|
| Overactive thyroid | TSH, free T4 | TSH low, free T4 raised |
| Early menopause | FSH, estradiol | FSH raised, estradiol low |
| Anemia or iron deficiency | Hemoglobin, ferritin | Ferritin low, sometimes normal Hb |
| Long-term stress | Cortisol | Unusual pattern across the day |
| Swinging blood sugar | Glucose, HbA1c | Heat some hours after eating |
| Medication | No blood value | Complaints began after a new prescription |
| Alcohol, caffeine, spicy food | No blood value | Heat within twenty minutes |
| Fever or infection | CRP, ESR | Inflammation values raised |
How many hot flashes per day is normal?
There is no agreed cut-off. In the primary care study by Mold, 8 percent of participants were bothered by them, and that bother weighed more than the count. One hot flash that wrecks your night counts for more than five you barely notice.
Tracking how often and when they arrive therefore says more than a number. A note on your phone is enough: time, how long, and what you did or ate beforehand.
After two weeks you usually see a pattern. That pattern is exactly what your GP needs.
Can stress cause hot flashes?
Yes. Under tension adrenaline is released, your blood vessels widen and your skin turns warm. This can happen within seconds, regardless of your hormone status. With ongoing stress, cortisol also plays a role, affecting your sleep and your temperature regulation among other things.
The awkward part is that stress and menopause reinforce each other. Sleeping badly makes you more sensitive to stress, and stress makes hot flashes heavier. Which of the two started is often impossible to say afterwards.
For completeness: the first symptoms of menopause can begin years before your last period. Stress and perimenopause do not rule each other out.
When should you have hot flashes looked at?
That is a conversation with your GP, not a fixed schedule. There are signals that make the conversation more urgent: hot flashes well before 40, weight loss without a clear reason, persistent fever, palpitations at rest, or night sweats that leave your bedding soaked.
Some women choose to have a few values measured first, so the conversation becomes more concrete. At Lunara you can for example have your estradiol tested, or look at individual values such as TSH.
My advice stays simple. Note down for two weeks when the heat arrives, take that list to your appointment, and ask explicitly whether your thyroid was included. That one sentence sometimes saves months.
Sources
- Freedman RR. Menopausal hot flashes: mechanisms, endocrinology, treatment. J Steroid Biochem Mol Biol. 2014. PMID 24012626.
- De Leo S, et al. Hyperthyroidism. Lancet. 2016. PMID 27038492.
- Nelson LM. Clinical practice. Primary ovarian insufficiency. N Engl J Med. 2009. PMID 19196677.
- Mold JW, et al. Night sweats: a systematic review of the literature. J Am Board Fam Med. 2012. PMID 23136329.
- Mold JW, et al. Prevalence and predictors of night sweats, day sweats, and hot flashes in older primary care patients: an OKPRN study. Ann Fam Med. 2004. PMID 15506569.
- Farmacotherapeutisch Kompas. Side effects per medicine. Available via farmacotherapeutischkompas.nl.
- Thuisarts.nl (NHG). I am going through menopause. Available via thuisarts.nl.
Every blood test result at Lunara includes a professional assessment by a BIG-registered doctor. For treatment decisions, discuss your results with your GP.
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