Ovaries May Wake Up After Menopause: SWAN Study Finds AMH Returns

Can Ovaries “Wake Up” After Menopause? New SWAN Data Says Yes

Nearly 54% of women in a large U.S. cohort showed a reappearance of anti-Müllerian hormone (AMH) after levels had already dropped below detection — and in about half of those cases, estradiol rose alongside it. The finding, from the landmark Study of Women’s Health Across the Nation (SWAN), published in Fertility and Sterility by Dr. Laura Bozzuto of the University of Wisconsin and colleagues, challenges the assumption that ovarian function simply switches off at the final menstrual period.

Hormone Levels Don’t Fall in a Straight Line

The reproductive hormone cascade most people picture — FSH rising as estradiol and AMH decline — is broadly correct over years, but noisy over months. AMH, secreted by small follicles in the ovary, is considered one of the best markers of ovarian reserve and typically becomes undetectable as menopause approaches. FSH climbs because the pituitary works harder to stimulate fewer remaining follicles, while estradiol, produced by those follicles, fluctuates erratically before falling.

Researchers have long known these fluctuations exist in perimenopause, but the assumption persisted that once AMH hits the floor, it stays there. Bozzuto’s team tested that assumption using ultrasensitive assays and repeated measurements from 406 SWAN participants who had an observed final menstrual period and at least one AMH reading below the detection limit.

What the SWAN Analysis Found: 54% Showed AMH Rebound

Of 1,558 SWAN participants with AMH data, 406 met the study’s criteria. Among them, 220 — 54.2% — had a detectable AMH value after previously falling below the limit. Among those women, 107 (48.6%) also showed a concurrent rise in estradiol, indicating that remaining follicles were not just present but actively producing estrogen.

Three characteristics separated women who rebounded from those who did not:

• Age at undetectable AMH: Women with both AMH and estradiol rebound reached the detection limit youngest (mean 48.5 years), versus 49.9 for AMH-only rebound and 51.7 for no rebound.
• BMI: Lower body mass index correlated with rebound (median BMI 24.5 kg/m² for AMH+E2 rebound vs. 27.5 for no rebound). Higher estrogen production in adipose tissue may partially suppress the residual follicular activity visible in leaner women.
• FSH at the AMH limit: Markedly lower in rebound groups (median ~29 mIU/mL) than in non-rebounders (62.5 mIU/mL), consistent with more residual ovarian function.

Notably, age at final menstrual period did not differ across groups — all around 52 years. Rebound did not delay menopause; it simply revealed that the road to it is bumpier than a single lab value suggests.

Why This Matters for Perimenopausal Staging and Symptoms

The hormonal physiology explains why perimenopause can feel chaotic. Follicles that remain late in the transition respond unevenly to FSH. When a cohort of follicles resumes growth, estradiol can spike to levels seen in the follicular phase of normal cycles — sometimes triggering unexpected estrogen-withdrawal bleeding, cyclic breast tenderness, or a temporary return of premenstrual-type symptoms after long stretches without them.

Clinically, the implications are real. A single “undetectable AMH” or one elevated FSH reading cannot confirm that menopause is complete, and a later estradiol rise doesn’t mean a woman wasn’t approaching menopause. Women who rely on lab values for contraception decisions or hormone therapy timing should know these numbers fluctuate. Pregnancy remains rare but possible until menopause is truly confirmed. Symptom patterns can also shift with these hormonal rebounds — which is relevant if you’re tracking FSH fluctuations and their link to bone loss, or evaluating whether to begin therapy, where current safety evidence on hormone therapy matters as much as timing.

Limitations deserve mention. The analysis required at least three AMH measurements and an observed final menstrual period, which selects for a specific subgroup; rebound frequency in the general population could differ. AMH assays vary in sensitivity, though the ultrasensitive assay used here strengthens the findings.

Practical Takeaways for Women and Clinicians

• Don’t anchor to one lab result. An undetectable AMH or high FSH reading may reverse, sometimes within months.
• Symptoms may return in waves. A resurgence of cyclical symptoms late in perimenopause can reflect genuine estradiol rebound, not imagination.
• Contraception decisions should rest on confirmed amenorrhea and clinical judgment, not isolated hormone values.
• Lean women and those reaching low AMH earlier are more likely to show rebound and may benefit from closer monitoring.

Frequently Asked Questions

Can AMH go back up after it becomes undetectable?

Yes — in this SWAN analysis, 54.2% of women with at least one undetectable AMH reading later had a detectable value again, and in about half of those cases estradiol rose too.

Does an AMH rebound mean menopause is delayed?

No. Age at final menstrual period was essentially identical across rebound and non-rebound groups (roughly 52 years), so rebound reflects fluctuating ovarian activity rather than extended fertility.

Why is rebound more common in leaner women?

Higher BMI is associated with more estrogen production outside the ovary, which may suppress residual follicular activity; the study found progressively lower BMI across the rebound groups.

Should I keep using contraception after AMH becomes undetectable?

Discuss it with your clinician, but yes — because ovarian activity can transiently resume, lab values alone can’t rule out occasional follicle development until menopause is clinically confirmed.

Ultimately, this study reframes menopause not as a switch but as a flickering dimmer. Ovaries can briefly re-engage even after hormone levels suggest they’ve shut down — a fact worth remembering with every perimenopausal lab draw.

Sources:
https://pubmed.ncbi.nlm.nih.gov/42320873/
https://pubmed.ncbi.nlm.nih.gov/42312311/
https://pubmed.ncbi.nlm.nih.gov/42254985/
https://pubmed.ncbi.nlm.nih.gov/42226203/
https://pubmed.ncbi.nlm.nih.gov/42218087/