Understanding Hormone Changes During Perimenopause

During perimenopause, the ovaries respond less consistently to signals from the brain. Follicle-stimulating hormone (FSH) rises. Estrogen swings, sometimes higher than usual, before it declines. Ovulation becomes less frequent, so progesterone falls in many cycles. These fluctuations, more than a steady drop, explain why perimenopause symptoms can be so unpredictable.

Which hormones change during perimenopause?

Estrogen is spelled "oestrogen" in the UK.

What happens to hormones, stage by stage?

Late reproductive years

The number of follicles in the ovaries falls throughout life. By the 40s, fewer follicles are growing each month, so they make less inhibin B. With less inhibin B holding it back, FSH starts to rise.

At this stage, the higher FSH works as compensation. Research from the Melbourne Women’s Midlife Health Project suggests the rise in FSH helps keep estradiol at near-normal levels until late in reproductive life. Periods may still look regular.

Early perimenopause

As follicle numbers fall further, the system becomes less stable:

• FSH swings. It may be high one month and normal the next.
• Estrogen becomes erratic. A review of menopause endocrinology notes that high FSH can drive estrogen to levels several times higher than in normal cycles. This can cause breast tenderness, heavier periods and worse premenstrual symptoms.
• Ovulation becomes less reliable, so some cycles produce little progesterone.

This is the stage when cycles begin to vary by a week or more. See early signs of perimenopause.

Late perimenopause

Ovulation becomes much less common. One long-term study found that the share of cycles with ovulation fell from about 60% to under 10% over the six years before the final period. In the final year, 60% to 70% of cycles either do not involve ovulation or have an unusually long first half.

Gaps between periods lengthen to 60 days or more, and estrogen begins a more sustained decline. See how long perimenopause lasts for the full timeline. Research tracking women over time found that AMH and inhibin B fall to undetectable levels about five years before the final period, while FSH roughly doubles.

After the final period

Estrogen continues to fall and may not reach its lowest point until one to two years after the final period. FSH is then consistently high, while inhibin B and AMH are undetectable.

What happens after surgery or cancer treatment?

Not everyone goes through the gradual changes described above:

• Removal of both ovaries causes an immediate drop in estrogen and progesterone, and a fall in the testosterone the ovaries make. This is sometimes called surgical menopause. Symptoms can start suddenly and may be more intense than in natural perimenopause.
• Hysterectomy with the ovaries kept stops periods, but the ovaries continue making hormones and go through the usual transition later. Because there are no periods to track, NICE advises identifying menopause from symptoms instead.
• Chemotherapy and pelvic radiotherapy can damage the ovaries and cause an earlier or sudden menopause, sometimes temporarily.

If you have had any of these treatments, ask your care team what hormone changes to expect and what support is available.

How do hormone changes cause symptoms?

• Heavy or irregular bleeding. When estrogen stimulates the womb lining without the regular progesterone that follows ovulation, the lining can build up more than usual and shed unpredictably. See heavy bleeding.
• Hot flashes and night sweats. Changing estrogen affects the brain’s temperature-control center in the hypothalamus, narrowing the range of temperatures the body tolerates comfortably. See hot flashes.
• Sleep and mood changes. Fluctuating estrogen and falling progesterone affect brain chemistry involved in mood and sleep. Research suggests these swings make some people more vulnerable to low mood and anxiety. See sleep problems and anxiety.
• Breast tenderness and worse PMS. Short-lived spikes in estrogen may be responsible in early perimenopause.
• Vaginal dryness and urinary changes. These tend to appear later, as estrogen settles at lower levels and the tissues become thinner and drier. See vaginal dryness.
• Lower sex drive. Hormone changes play a part, along with sleep, mood, relationship factors and vaginal discomfort. See low libido.

Why can hormone test results look "normal"?

Because perimenopause is defined by fluctuation, a blood test shows only one moment. You could have a normal FSH one week and a high one the next, or an estrogen level that is higher than usual even though you have symptoms.

This is why the UK’s National Institute for Health and Care Excellence (NICE) advises against using hormone tests to identify perimenopause in people aged 45 or over who have typical symptoms. A normal result does not rule perimenopause out, and a single high result does not confirm it. See perimenopause tests.

What about "hormone imbalance" claims?

You may see perimenopause described as a "hormone imbalance" that can be fixed with specific supplements, diets or detailed hormone panels. A few points are worth knowing:

• Fluctuation is expected. Changing hormone levels in perimenopause are a normal part of the transition, not a disorder to be "rebalanced" with a product.
• Commercial hormone panels have limits. Because levels swing, one set of results cannot map your hormones reliably or guide treatment on its own.
• Terms such as "estrogen dominance" are widely used online but are not how major clinical guidelines describe perimenopause. The pattern is better understood as erratic estrogen alongside less frequent ovulation.

If a product promises to "balance your hormones," ask what evidence supports it and whether it has been tested in people in perimenopause.

How do treatments affect these hormones?

• Hormone therapy (HRT) replaces estrogen. People who still have a womb also need a progestogen, which protects the lining from thickening. In perimenopause, a cyclical regimen that produces a monthly bleed is commonly used.
• Combined hormonal contraception replaces your natural cycle with a steady dose of hormones. This can smooth out fluctuations and is sometimes used instead of HRT in people under 50.
• The hormonal IUD releases progestogen locally, reducing heavy bleeding and protecting the womb lining when used as part of HRT.
• Non-hormonal treatments work on symptoms through other pathways. Fezolinetant, for example, acts on the brain’s temperature-control center.

The right choice depends on your symptoms, health history and preferences. For an overview, see our perimenopause guide.

Questions to ask your clinician

1. Which of my symptoms are likely to be caused by hormone changes, and which might have another cause?
2. Would any hormone test change what we do next?
3. Which treatment options would suit my stage of perimenopause?
4. If I have had surgery or cancer treatment, how does that change my options?

Frequently asked questions

Does estrogen go up or down in perimenopause?

Both. Estrogen often swings higher and lower than usual during perimenopause, before falling more steadily in late perimenopause and after the final period.

Is low progesterone a sign of perimenopause?

Lower progesterone is expected in perimenopause because ovulation happens less often. It isn’t used to diagnose perimenopause, because levels depend on where you are in your cycle and whether you ovulated that month.

Does testosterone drop at menopause?

Testosterone declines gradually with age, mostly before menopause, rather than falling sharply at menopause. Surgical removal of the ovaries is an exception, as it causes a more sudden drop.

Can hormone levels tell me how long perimenopause will last?

No. Hormone levels vary too much during the transition to predict how long it will last or when your final period will be.

References

1. Burger HG et al. A review of hormonal changes during the menopausal transition: Melbourne Women’s Midlife Health Project. Human Reproduction Update, 2007
2. Endocrinology of the menopause (review), PMC
3. Endocrine Society: Hormonal changes in the menopause transition
4. International Menopause Society: FSH, estradiol, AMH and inhibin B in the menopausal transition
5. The American Journal of Medicine: The menopausal transition
6. FSRH guideline: Contraception for women aged over 40 years
7. NICE guideline NG23: Menopause, identification and management
8. Worcestershire Acute Hospitals NHS Trust: Your journey through the perimenopause and menopause (patient information)
9. FSRH Contraception Choices: Perimenopause and menopause
10. Menopause-associated depression (review), PMC
11. University of Utah Health: Skip the misleading at-home menopause tests

Editorial status: evidence-based educational article. Last evidence check: September 10, 2026.