Updated September 2026: this article uses the condition’s new name — PMOS (Polyendocrine Metabolic Ovarian Syndrome) — announced in The Lancet on 12 May 2026. The older name PCOS is still used where older guidelines and studies use it.
For decades the condition was called polycystic ovary syndrome, or PCOS. In May 2026, a global consensus published in The Lancet gave it a new name: polyendocrine metabolic ovarian syndrome, or PMOS. The change reflects something clinicians have known for years — the condition is not really about cysts, and it affects far more than the ovaries.
Many hormone systems
Not just ovarian hormones — insulin, androgens and others are involved.
Body-wide effects
Insulin resistance, weight, and long-term heart and diabetes risk.
Cycles and ovulation
Irregular periods and fertility remain a core part of the condition.
women affected — more than 170 million worldwide
of affected women are undiagnosed, according to WHO
Rotterdam criteria needed for a diagnosis
target for full adoption in the international guideline
The short version
- PMOS is the new name for PCOS. The condition, diagnosis and treatment are the same — only the name has changed.
- A diagnosis needs 2 of 3 features: irregular or absent ovulation, signs of high androgens, or polycystic-appearing ovaries on ultrasound.
- Insulin resistance is common, which is why diet, exercise and metabolic care matter so much.
- Metformin has the strongest evidence among the non-hormonal medicines for metabolic features; inositol’s benefits look smaller.
- For ovulation induction, letrozole produced more live births than clomiphene in a large trial.
Why the name changed
The name “polycystic ovary syndrome” dates back to early descriptions of the condition, but the 2003 Rotterdam criteria made clear that visible cysts are not required for a diagnosis. The word “polycystic” had become misleading: many people were diagnosed without cysts, and many others spent years focused on their ovaries while the metabolic side was missed.
According to the Endocrine Society, the renaming took 14 years and involved more than 50 patient and professional organisations, over 22,000 survey responses and a series of international workshops. The results were published in The Lancet on 12 May 2026. A three-year transition has started, with full adoption planned for the 2028 update of the international guideline.
How common is it
The World Health Organization estimates that the condition affects 10–13% of women of reproductive age, and that up to 70% of those affected do not know they have it. It is one of the most common hormonal conditions in people with ovaries and a leading cause of irregular periods and difficulty conceiving.
Symptoms
PMOS looks different from person to person. The most common features are:
Irregular or absent periods
Cycles longer than 35 days, or fewer than 8 periods a year. Some people have none at all.
Signs of high androgens
Acne, excess facial or body hair, or scalp hair thinning. Blood tests may show raised testosterone.
Polycystic-appearing ovaries
Many small follicles on ultrasound. This finding is neither required nor enough on its own.
Weight changes
Weight gain and difficulty losing weight are common, but lean people can have PMOS too.
Mood and energy
Fatigue, low mood and anxiety are commonly reported and are more frequent in people with PMOS.
How it is diagnosed
Rotterdam criteria: a diagnosis needs at least two of these three features, after other causes have been ruled out.
- Ovulation problemsIrregular or absent ovulation, shown by irregular periods or blood tests.
- High androgensClinical signs (acne, excess hair) or raised androgen levels in blood tests.
- Ovary appearancePolycystic-appearing ovaries on a pelvic ultrasound.
Conditions that cause similar symptoms — thyroid disorders, high prolactin and congenital adrenal hyperplasia — need to be ruled out first. Diagnosis is usually made by a gynaecologist or endocrinologist using a physical examination, blood tests and ultrasound. The American College of Obstetricians and Gynecologists notes that irregular cycles are normal in the first years after a first period, so diagnosis in adolescents needs extra care.
The role of insulin resistance
Insulin resistance means the body’s cells respond less well to insulin, so the pancreas makes more of it. It is common in PMOS — including in people who are not overweight — and high insulin levels can push the ovaries to produce more androgens. This link is why PMOS carries a higher risk of type 2 diabetes and metabolic syndrome, and why treatments that improve insulin sensitivity can also ease hormonal symptoms.
What the evidence says about treatment
Treatment depends on what matters most to you — regular cycles, skin and hair symptoms, metabolic health or fertility. Here is how the main options compare:
| Option | Mainly helps with | Evidence |
|---|---|---|
| Lifestyle changes | Insulin sensitivity, metabolic health, cycles | First-line Recommended for everyone with PMOS |
| Metformin | Metabolic features, weight, cycle regularity | Guideline-backed Especially for adults with a higher BMI |
| Combined pill | Periods, acne, excess hair | Well established Does not treat metabolic features |
| Letrozole | Ovulation and fertility | Strong trial data More live births than clomiphene |
| Inositol | Metabolic markers | Limited Smaller benefits in a 2026 network meta-analysis |
Lifestyle changes
Diet and physical activity are the foundation of care. A 2019 systematic review in Systematic Reviews found that exercise improved several metabolic and cardiovascular markers in women with PCOS, including fasting insulin, cholesterol and fitness — though many of the effects were modest. The international guideline notes that in people with excess weight, even a small loss of body weight can bring meaningful improvements. The goal is better metabolic health, not a particular body size.
Metformin
Metformin is an insulin-sensitising medicine used for type 2 diabetes and, off-label, for PMOS. The 2023 international evidence-based guideline recommends it alongside lifestyle changes for adults to improve metabolic outcomes, particularly those with a higher BMI. Stomach upset is the most common side effect and is usually reduced by starting at a low dose.
Inositol
Myo-inositol is a compound involved in insulin signalling and is sold as a supplement. Some small trials have reported improvements in insulin sensitivity and ovulation, but the overall evidence is weaker than for metformin. A 2026 network meta-analysis in Frontiers in Endocrinology found that GLP-1 receptor agonists combined with metformin were the most effective for weight and BMI reduction, while inositol showed only small metabolic benefits. Because supplements are not regulated like medicines, doses and quality vary.
Hormonal contraceptives
Combined oral contraceptive pills are commonly used to regulate periods and reduce acne and excess hair. They do not treat the metabolic side of PMOS, but they suit people who also want contraception or have troublesome symptoms. Anti-androgen medicines such as spironolactone are sometimes added for persistent hair growth or acne.
Fertility treatment
PMOS is a leading cause of infertility due to absent ovulation, but most people with the condition can conceive with treatment. In a large randomised trial published in the New England Journal of Medicine in 2014, letrozole led to more live births than clomiphene in women with PCOS, and it is now widely used as the first choice for ovulation induction.
Long-term health risks
PMOS is linked with higher rates of type 2 diabetes, high blood pressure and heart disease over time, largely driven by insulin resistance. Anxiety and depression are also more common.
Why regular periods matter: when periods are very infrequent, the lining of the womb is not shed regularly, which raises the risk of endometrial hyperplasia and endometrial cancer. This is one reason doctors aim to bring on a period several times a year, even when someone is not trying to conceive.
What the name change means for you
The name — gradually
- New reports and guidelines will start using PMOS
- More focus on metabolic screening, not just the ovaries
- Full adoption planned for the 2028 guideline update
Your diagnosis and care
- A PCOS diagnosis is the same condition as PMOS
- The same diagnostic criteria still apply
- Your treatment plan does not need to change
During the transition you may see PCOS and PMOS used side by side, in clinics, lab reports and articles. Both refer to the same condition.
Frequently asked questions
Is PMOS a different condition from PCOS?
No. PMOS is simply the new name for PCOS. The condition, the way it is diagnosed and the treatments are unchanged.
Do I need a new diagnosis?
No. If you were diagnosed with PCOS, you have the condition now called PMOS. There is no need for new tests because of the name change.
Can you have PMOS without cysts on your ovaries?
Yes. Ovary appearance on ultrasound is only one of three criteria, and a diagnosis needs any two of them. This mismatch was one of the main reasons for the new name.
Can PMOS be cured?
There is no cure, but symptoms and long-term risks can be managed well with lifestyle changes and, where needed, medicines such as metformin, the combined pill or fertility treatment.
Sources
- Polyendocrine metabolic ovarian syndrome, the new name for polycystic ovary syndrome: a multistep global consensus process. The Lancet, 2026.
- Endocrine Society. Polyendocrine Metabolic Ovarian Syndrome: new name to improve diagnosis and care of condition affecting 170 million women worldwide. May 2026.
- World Health Organization. Polycystic ovary syndrome — fact sheet.
- American College of Obstetricians and Gynecologists. Polycystic Ovary Syndrome — Practice Bulletin. 2018.
- Forslund M et al. International evidence-based guideline on assessment and management of PCOS — A Nordic perspective. Acta Obstetricia et Gynecologica Scandinavica, 2024.
- Kite C et al. Exercise, or exercise and diet for the management of polycystic ovary syndrome: a systematic review and meta-analysis. Systematic Reviews, 2019.
- Omarion A et al. Comparative analysis of GLP-1 receptor agonists, metformin, and inositol in improving anthropometric and metabolic outcomes in women with polycystic ovary syndrome: a network meta-analysis. Frontiers in Endocrinology, 2026.
- Legro RS et al. Letrozole versus clomiphene for infertility in the polycystic ovary syndrome. New England Journal of Medicine, 2014.
This article is for general information only and is not a substitute for advice from your doctor or gynaecologist. See our medical disclaimer.
