Estrogen and Hot Flashes: Why Falling Estrogen Turns Up the Heat

Estrogen and hot flashes are tightly linked: as estrogen falls, a small cluster of brain cells called KNDy neurons becomes overactive and tells your temperature center to dump heat, even when you aren’t actually too warm. Researchers think it’s the drop and swings in estrogen, more than the level itself, that turn up the heat, which is why hot flashes often start in perimenopause.

Disclosure: My husband, Brandon, does freelance marketing work for Immunotec, the company that makes She+. I got She+ free as an early tester.

What estrogen has to do with body temperature

Most of us think of estrogen as a reproductive hormone, but it also talks to the hypothalamus, the part of your brain that works like a thermostat. Mayo Clinic explains that lower estrogen seems to make the hypothalamus overreact to small temperature changes (Mayo Clinic).

Here’s the simple version. Your thermostat keeps your core temperature inside a band. Above it, you sweat. Below it, you shiver. Researcher Robert Freedman found that in women with hot flashes, this band gets much narrower, so tiny rises in core temperature trigger a full heat-dumping response. He also found that estrogen eases hot flashes by raising the temperature at which sweating kicks in, which widens the band back out (Semin Reprod Med, 2005; J Steroid Biochem Mol Biol, 2014). For the full picture of what a flash is and what triggers one, see what causes hot flashes.

KNDy neurons, explained simply

Deep in the hypothalamus is a small group of nerve cells nicknamed KNDy (say “candy”) neurons. The name comes from three chemical messengers they make: kisspeptin, neurokinin B and dynorphin. Normally, estrogen keeps these cells in check.

When estrogen falls, three things happen:

1. They grow. Studies of brain tissue found these neurons are enlarged in women after menopause, and they make more kisspeptin and neurokinin B. When young monkeys lost their ovaries, the same changes happened, and giving estrogen back reversed them (Front Neuroendocrinol, 2013).
2. They get louder. A 2025 review describes KNDy neurons becoming hyperactive as estradiol (the main form of estrogen) decreases (Temperature, 2025).
3. They reach the heat controls. These neurons connect to the area of the hypothalamus that turns on heat loss, including opening blood vessels in the skin and sweating, the two signature features of a hot flash. Neurokinin B acts there through a receptor called NK3 (Temperature, 2025).

So the picture is a little like a smoke alarm that got more sensitive. With less estrogen to quiet it, the alarm goes off at the faintest whiff of warmth, and your body responds as if it’s overheating.

Why the swings in perimenopause matter

Here’s the part that surprised me. Researchers have found that it isn’t simply how much estrogen you have. Freedman noted that estrogen levels don’t differ between women who have hot flashes and women who don’t (Semin Reprod Med, 2005). Instead, the 2025 review explains that the rate of estrogen withdrawal seems to determine when hot flashes start (Temperature, 2025).

That helps explain a few things:

• Perimenopause is bumpy. Mayo Clinic describes estrogen rising and falling during perimenopause (Mayo Clinic). Hormone changes during this stage are nonlinear, and ovulatory cycles can still happen, so every drop can stir up symptoms.
• Some women notice flashes before a period. The same review notes hot flashes can show up in the late part of the cycle, when hormone levels begin to decline.
• Sudden loss hits hardest. Women who have their ovaries removed often get severe, frequent hot flashes, because estrogen drops all at once.

It also fits the SWAN study, which followed more than 3,000 US women. Women who first had frequent hot flashes while still premenopausal or early in perimenopause had them the longest, a median of more than 11.8 years, while women whose flashes started after menopause had them for a median of 3.4 years (JAMA Internal Medicine, 2015).

My own symptoms began about a year ago in perimenopause: low energy first, then slipping sleep, then hot flashes and nights where I woke up hot and sweaty. You can see how hot flashes fit with all the other changes on my perimenopause symptoms list.

Why falling estrogen affects sleep too

Nighttime hot flashes, or night sweats, are the same process happening while you sleep. In SWAN, more frequent hot flashes were linked to more trouble falling and staying asleep, and women using hormones generally had lower odds of disturbed sleep (Sleep, 2008). My guide to night sweats goes deeper.

Options that work on this pathway

Replacing estrogen: hormone therapy

Menopausal hormone therapy gives back some of the estrogen your body is making less of, which calms the system at its source. A Cochrane review of 21 trials found oral hormone therapy reduced weekly hot flash frequency by 77% compared with placebo (Cochrane, 2001). Women with a uterus also take a progestogen. Risks such as blood clots, stroke and breast cancer depend on your age and health history, so it’s a conversation to have with your doctor (NIA).

Blocking the KNDy signal: fezolinetant and elinzanetant

The KNDy discovery led directly to a new kind of medicine. Fezolinetant (Veozah), approved by the FDA in May 2023, blocks the NK3 receptor that neurokinin B uses in the brain’s temperature center. It requires liver blood tests before and during the first months of use (FDA). Elinzanetant blocks both NK1 and NK3 receptors and is also approved for moderate to severe hot flashes (Cleveland Clinic).

Other prescriptions

Low-dose paroxetine is FDA-approved for hot flashes, and doctors also use other SSRIs, SNRIs and gabapentin. I compare them all in hot flash treatments.

Plant-based support

Red clover contains isoflavones, plant compounds whose structure resembles estrogen (NCCIH). A 2021 meta-analysis found about 1.7 fewer hot flashes a day compared with placebo (Nutrients, 2021). Black cohosh, the most studied menopause herb, improved hot flashes compared with placebo in a 2023 meta-analysis of 22 studies (Menopause, 2023). More in herbal remedies for hot flashes.

What I use

I take She+ by Immunotec, an apple blueberry jelly stick with black cohosh, red clover, ginger and glucomannan. To be clear, She+ isn’t hormone replacement therapy (HRT). It’s a daily supplement made with plant extracts. Magnesium didn’t help me, but after about two months on She+, my Oura sleep scores went from constant wake-ups to the 80s and 90s, my energy came back, and my hot flashes have eased a lot. Individual results vary. I share everything in my She+ review.

Talk to your doctor if

• You’re considering hormone therapy. Share your personal and family history, including blood clots, stroke, heart disease and breast cancer.
• You’ve had breast or uterine cancer. This shapes which hormonal and herbal options are safe, including black cohosh and red clover (NCCIH).
• You have liver problems. Fezolinetant needs liver monitoring, and black cohosh has rare liver reports. Stop black cohosh and call your doctor if you notice yellowing skin or dark urine (NIH ODS).
• You take blood thinners or are pregnant. Ginger can interact with warfarin (BJCP, 2021), and black cohosh and red clover aren’t for pregnancy.
• Your symptoms seem off. Hot flashes can also come from thyroid problems, medications or other conditions, and drenching night sweats with fever or weight loss should be checked.

Frequently asked questions

Does low estrogen cause hot flashes?

Falling estrogen is the main driver. Research suggests the drop and the swings matter more than the level itself, which is why hot flashes often start in perimenopause.

What are KNDy neurons?

A small group of brain cells in the hypothalamus that make kisspeptin, neurokinin B and dynorphin. Without enough estrogen to keep them quiet, they become overactive and trigger heat-loss responses like flushing and sweating.

Why do I get hot flashes if I’m still having periods?

In perimenopause, estrogen rises and falls rather than dropping in a straight line. Each dip can set off symptoms.

Does estrogen therapy stop hot flashes?

It’s very effective for many women. A Cochrane review found a 77% reduction in hot flash frequency compared with placebo. Your doctor can help you weigh the benefits and risks.

Is She+ a form of estrogen or HRT?

No. She+ isn’t hormone replacement therapy (HRT). It’s a daily supplement made with plant extracts, including black cohosh and red clover. I cover what’s in it and how it worked for me in my She+ review.

Sources

1. Hot flashes: symptoms and causes. Mayo Clinic. Mayo Clinic
2. Perimenopause: symptoms and causes. Mayo Clinic. Mayo Clinic
3. Freedman RR. Pathophysiology and treatment of menopausal hot flashes. Semin Reprod Med, 2005. PubMed
4. Freedman RR. Menopausal hot flashes: mechanisms, endocrinology, treatment. J Steroid Biochem Mol Biol, 2014. PubMed
5. Rance NE, et al. Modulation of body temperature and LH secretion by hypothalamic KNDy neurons: a novel hypothesis on the mechanism of hot flushes. Front Neuroendocrinol, 2013. PMC
6. Effects of menopause on temperature regulation. Temperature, 2025. PubMed
7. Duration of menopausal vasomotor symptoms over the menopause transition (SWAN). JAMA Intern Med, 2015. PubMed
8. Sleep disturbance during the menopausal transition in a multi-ethnic community sample of women (SWAN). Sleep, 2008. PubMed
9. Oral oestrogen replacement therapy versus placebo for hot flushes. Cochrane Database Syst Rev, 2001. PubMed
10. Hot flashes: what can I do? National Institute on Aging. NIA
11. FDA approves novel drug to treat moderate to severe hot flashes caused by menopause. US Food and Drug Administration, 2023. FDA
12. Hot flashes. Cleveland Clinic. Cleveland Clinic
13. Red clover. National Center for Complementary and Integrative Health. NCCIH
14. Clinical meaningfulness of red clover extract to relieve hot flushes. Nutrients, 2021. PubMed
15. Black cohosh extracts in women with menopausal symptoms: an updated pairwise meta-analysis. Menopause, 2023. PubMed
16. Black cohosh fact sheet for health professionals. NIH Office of Dietary Supplements. NIH ODS
17. Black cohosh. National Center for Complementary and Integrative Health. NCCIH
18. Warfarin and food, herbal or dietary supplement interactions: a systematic review. Br J Clin Pharmacol, 2021. PubMed

This article reflects one person’s experience and is for general information only. It is not medical advice. Talk with your healthcare provider before starting any supplement. *These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.