Hot flashes and hormone therapy: the science of perimenopause

Summary of Hot flashes and hormone therapy: the science of perimenopause

by Science Friday and WNYC Studios

18m•September 17, 2026
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Overview of Hot flashes and hormone therapy: the science of perimenopause

This Science Friday episode breaks down what actually happens during perimenopause, why symptoms vary so much from person to person, and how hormone therapy went from widely prescribed to highly controversial — and back toward more nuanced use. Host Flora Lichtman speaks with two leading researchers, Dr. Nanette Santoro and Dr. Genevieve Neal-Perry, about the biology of hot flashes, the long-term findings from major menopause studies, and the dangers of overpromising “miracle” treatments online.

What Perimenopause Is Doing to the Body

Hormonal fluctuations, not a simple “decline”

  • Perimenopause is the transition period before menopause when hormone levels swing up and down, rather than just steadily dropping.
  • It can affect the whole body, not just reproductive health.
  • Common symptoms include:
    • hot flashes
    • sleep disruption
    • mood changes
    • brain fog
    • bone density loss
    • body-wide discomfort or aches

Symptoms vary widely

  • Some people are heavily affected; others barely notice changes.
  • Researchers emphasized that symptom severity is shaped by more than hormones alone.
  • People who tend to have worse symptoms may include those with:
    • higher baseline pain sensitivity
    • more financial stress
    • more social stress
    • worse overall social determinants of health
  • Racial and ethnic differences also appear in symptom timing and severity.

The Science of Hot Flashes

Brain circuits are involved

  • Hot flashes are linked to estrogen’s effects on neurons in the brain that regulate temperature perception.
  • Dr. Neal-Perry described a key group of neurons, commonly known as KNDy neurons (the transcript rendered this imperfectly), which become more active when estrogen is absent or fluctuating.
  • These neurons increase neurokinin signaling, which helps trigger the heat-sensation cascade that produces hot flashes.

It’s not just “low estrogen”

  • A key insight: hot flashes often peak during the menopause transition, when estrogen is variable, not simply low.
  • That suggests a more dynamic brain-hormone interaction than a basic deficiency model.
  • For most women, the brain eventually adapts:
    • about 85–90% see hot flashes improve over time
    • about 5–10% continue to have severe hot flashes long-term

The History of Hormone Therapy

Why it became controversial

  • The Women’s Health Initiative (WHI) strongly shaped public perception of hormone therapy.
  • WHI was designed to study whether estrogen therapy:
    • reduced heart disease
    • improved cognition
    • increased breast cancer risk
  • The key problem, according to the guests, was that the results were applied too broadly to women who were not the population studied.

What WHI actually showed

  • Hormone therapy was not cardioprotective in the older women studied.
  • It did not improve cognition in older women.
  • It did show an increased breast cancer risk, along with blood clot risk — but these risks were not new discoveries.
  • The main issue was that the findings were generalized to all menopausal women, creating fear and a major drop in prescribing.

What later follow-up changed

  • Longer follow-up of WHI participants showed:
    • no major change in mortality overall
    • no huge long-term disease signal
    • more favorable results for women who started therapy around ages 50–60, when hot flashes are most common
  • This helped re-open the door to more selective, individualized hormone therapy use.

Where the Field Is Now

More openness, but also more hype

  • The guests agreed that perimenopause is finally getting more attention, which is good.
  • But they also warned that the moment is being exploited commercially.
  • Concerns include:
    • hormone therapy being promoted as the answer to everything
    • unproven “bioidentical” claims
    • peptides and other treatments sold without evidence
    • testosterone being marketed as a universal fix

Key caution

  • Their message: if it sounds too good to be true, it probably is.
  • Hormone therapy can be helpful, but it is not a cure-all.
  • Patients still need a broad toolkit, including non-hormonal approaches and individualized care.

Main Takeaways

  • Perimenopause is a real, body-wide transition with variable symptoms.
  • Hot flashes are driven by brain-based thermoregulation changes, not just “low estrogen.”
  • The WHI was important but was misinterpreted and overgeneralized.
  • Hormone therapy is useful for some people, especially for symptom relief, but it has risks and limitations.
  • Social media has helped raise awareness, but it has also amplified misinformation and sales tactics.
  • The best approach is evidence-based, individualized treatment rather than one-size-fits-all promises.

Notable Insights

  • “Perimenopause is not women quietly fading out; hormones fluctuate dramatically.”
  • Many symptoms people attribute to perimenopause may be real, but not all are directly caused by hormone changes.
  • The biggest danger right now may be not just under-treatment, but over-selling therapies that lack evidence.