PMOS (a newer name for PCOS)

Key points

What it is

PMOS (polyendocrine metabolic ovarian syndrome) is a common hormonal condition in women of reproductive age, affecting the ovaries and a wide range of body systems. In May 2026 an international consensus of 56 organisations renamed PCOS (polycystic ovary syndrome) as PMOS.¹

‘Polyendocrine’ means several hormone systems are involved; ‘metabolic’ highlights insulin and energy use; ‘ovarian’ reflects effects on ovulation and fertility.

The NHS now uses the new name,⁴ and many clinics still say PCOS during the changeover.¹ The old name is misleading on two counts. It is not really about "cysts" at all: the ovaries contain many small, immature follicles rather than true cysts.¹ And naming it after the ovaries hides the fact that metabolism sits at the centre of it. This article uses PMOS throughout. The condition is the same one. NICE is preparing its own PMOS guideline, expected in January 2027, and this article will be checked against it.

PMOS is best understood as a syndrome with three threads: disrupted ovulation (causing irregular periods and reduced fertility); raised androgen hormones (such as testosterone, causing acne, excess hair, or scalp-hair thinning); and underlying insulin resistance, which often drives the other two.

Not everyone has the same pattern: some have mainly ovulation issues, some mainly androgen symptoms, and some both; insulin resistance is common across these patterns.

What causes it, and who is at risk

The exact cause is not fully known, but insulin resistance and high insulin are thought to be central in most women.^2,3 High insulin stimulates the ovaries to produce more androgen hormones, such as testosterone, and disrupts normal ovulation, producing many of the features. There is a strong genetic and family component: having a close relative with PMOS increases your chance of having it.⁴ PMOS occurs in people of all body sizes, and its long-term risks apply whatever your weight.² Carrying excess weight can make insulin resistance and symptoms worse. PMOS also occurs in lean women, and most of them have insulin resistance too.³ Factors that can worsen insulin resistance, such as poor sleep, chronic stress and some medicines, may also add to it.

Symptoms and signs

Symptoms vary widely.⁴ Common features include:

• Irregular, infrequent, or absent periods.
• Difficulty conceiving (due to reduced or absent ovulation).
• Signs of raised androgens: acne, excess facial or body hair (hirsutism), or scalp hair thinning.
• Weight gain or difficulty losing weight, especially around the waist.
• Signs of insulin resistance: dark skin patches in armpits, groin and on the neck (acanthosis nigricans) and skin tags.
• Low mood, anxiety, and reduced quality of life. (Mood symptoms are common and treatable; tell your clinician if anxiety or low mood are affecting you.²)
• Loud snoring with unrefreshing sleep or daytime tiredness. Sleep apnoea is more common in PMOS, whatever your weight, and is worth mentioning to your clinician.²

How it is diagnosed

PMOS is diagnosed when at least two of these three are present: (1) irregular or absent ovulation and periods; (2) signs or blood tests showing raised androgens (testosterone); (3) polycystic-appearing ovaries on ultrasound. However, these are not actual harmful cysts in the ovaries; they are small follicles. Other conditions that can look similar are ruled out first.² If periods are irregular and androgens are raised, a scan is not needed. In adults a blood test (AMH) can replace the ultrasound. In teenagers neither the scan nor AMH is used, and both irregular periods and raised androgens are required.²

The metabolic health perspective

The name PMOS was chosen to highlight the metabolic and multi-hormone nature of the condition, not just the ovaries. In most women, insulin resistance is thought to drive many of the features: the body compensates for reduced insulin sensitivity by producing more insulin, and this excess insulin acts directly on the ovaries, pushing them to produce more androgens and disrupting normal ovulation. High insulin also promotes weight gain, particularly around the waist, which can then worsen insulin resistance further, a self-reinforcing cycle. This is why PMOS so often occurs alongside a larger waist. It also raises the long-term risk of type 2 diabetes and related conditions.² Because of this cycle, improving insulin sensitivity can break the loop and improve periods, skin, and long-term health.

PMOS is not a single, uniform condition. Some women with PMOS have normal insulin sensitivity, and their symptoms are driven more by other hormonal factors; this matters because it affects which treatments are likely to help most. But insulin resistance is present in a large majority of women with PMOS, including most lean women,³ so checking metabolic health is useful regardless of body size. Where insulin resistance is a driver, reducing it can help: periods often become more regular, ovulation and fertility improve, skin and hair symptoms ease, and long-term metabolic risk falls. This is true for lean women with PMOS as well, where the focus is on insulin sensitivity rather than weight loss specifically.

Treatment and management

Treatment is tailored to your goals (for example: regular periods, clearer skin, or getting pregnant) and to whether insulin resistance is a driver. It combines lifestyle change, other options and medication.

Lifestyle and the Health Foundations

Lifestyle change targets insulin resistance directly, which is why it is usually the first treatment offered, alongside any specific medical options needed.

Nutrition

Cutting sugary drinks and ultra-processed snacks often gives the biggest insulin reduction benefit. A focus on building meals with plenty of protein and non-starchy vegetables can be helpful, with starchy carbohydrate such as bread, rice, pasta and potatoes reduced or personalised. This pattern asks less of your insulin system and often improves periods, ovulation and androgen symptoms. Try this as a starting point and adjust based on how you feel. International guidance does not single out one diet; it asks for a sustainable healthy pattern tailored to you, and notes benefits even without weight loss.² The approach above is one way to reduce how much insulin your body needs to release after meals. Where there is excess weight, weight management brings real clinical improvement,² and in practice even modest loss often brings back more regular periods and ovulation; improving insulin sensitivity through diet and activity helps lean women too, and matters for fertility as well as symptom control. The 28 Day Plan framework may be a useful approach.

Movement and muscle

Regular activity improves insulin sensitivity directly, independent of weight change. Aim for at least 150 to 300 minutes of moderate activity a week (or 75 to 150 minutes of vigorous activity), plus muscle-strengthening sessions on two separate days a week,² for example 20 to 30 minutes each, to build muscle, which increases the body's capacity to clear glucose from the blood. Moderate activity includes brisk walking, cycling, or swimming. Resistance sessions can use bodyweight, bands, or weights.

Sleep and stress

Poor sleep and chronic stress both worsen insulin resistance. Aim for 7 to 9 hours of sleep a night. Keep a regular sleep schedule and limit screens before bed to improve sleep quality. Build in regular activity or relaxation to manage stress. Try brief daily relaxation (breathing exercises, a short walk, or mindfulness) to lower stress.

Other non-pharmaceutical options

• Inositol supplements are widely sold for PMOS. The 2023 guideline says they can be considered as a personal choice: harm is limited and some metabolic measures may improve, but the benefit for ovulation, hair or weight is limited, and no particular type or dose can be recommended. Tell your clinician if you take it, especially if trying to conceive.²
• Some supplements can interact with medicines or affect early pregnancy; always check with your clinician before starting.

Medical and pharmaceutical treatments

• Metformin improves insulin sensitivity and can help periods and ovulation. The guideline advises considering it for adults with a BMI of 25 or more for metabolic benefit, notes it works about as well as an active lifestyle programme, and says it can also be considered at lower BMI, though the evidence there is limited.²
• Weight-loss injections (GLP-1 medicines such as semaglutide) can be considered alongside lifestyle change for adults with PMOS and a higher weight, as in general obesity care. Reliable contraception is needed while taking them because safety in pregnancy is unknown,² and your clinician will advise on stopping them before you try to conceive.
• The combined contraceptive pill is used to regulate periods and reduce androgen symptoms (when not trying to conceive).²
• Anti-androgen medicines (such as spironolactone) can help hair and acne. They are usually tried if six months of the pill or cosmetic treatment has not been enough, and always with effective contraception because they can affect the development of a male baby's genitals.²
• Screening and managing the metabolic risks (blood sugar, blood fats, blood pressure) is part of long-term care.

These medicines are generally not licensed specifically for PMOS; they are used on the evidence, off-label, so your clinician will explain the pros and cons.² These options are summaries for understanding; decisions and prescriptions rest with your clinician.

Complications and outlook

PMOS is linked to a higher long-term risk of heart and blood vessel disease, partly via insulin resistance, blood fats and blood pressure, although the overall risk of heart disease before the menopause is low.² There is also a greater risk of type 2 diabetes and gestational diabetes,² and of fatty liver.⁴ Long gaps between periods also raise the risk of thickening and cancer of the womb lining. The overall chance is low, and regular periods, weight management or progestogen (hormone) treatment help reduce the risk.² Blood sugar should be checked at diagnosis and then every one to three years depending on other risk factors (the guideline prefers a glucose tolerance test; the HbA1c average blood sugar test is often used in practice but is less accurate), blood pressure every year, and blood fats at diagnosis.² Mood and quality of life are commonly affected.²

The outlook can be positive. Because insulin resistance is so often the driver, improving metabolic health can reduce both day-to-day symptoms and long-term risks, and many women conceive with the right support.

When to see a doctor

• See a doctor about irregular or absent periods, troublesome acne or excess hair, or difficulty conceiving.
• Ask for assessment of metabolic health (blood sugar, blood fats and blood pressure).
• If you plan pregnancy, ask for a check-up before trying for a baby, to review medicines, supplements and metabolic health.

Summary