PMOS (Previously known as 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. It was previously known as PCOS (Polycystic Ovary Syndrome).

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

PCOS is still the name used in most clinics. It is misleading on two counts. It is not really about "cysts" at all: the ovaries contain many small, immature follicles rather than true cysts. And naming it after the ovaries hides the fact that metabolism sits at the centre of it. PMOS is the newer name, and this article uses it throughout. The condition is the same one.

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 central. 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 mother or sister with PMOS increases your chance of having it. PMOS occurs in people of all body sizes. Carrying excess weight can make insulin resistance and symptoms worse, but many people with PMOS are lean. Risk and severity can also be increased by factors that worsen insulin resistance, such as poor sleep, chronic stress, and some medicines.

Symptoms and signs

Symptoms vary widely. 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.)

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.

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 the most common form, insulin resistance drives 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, and why it markedly raises the long-term risk of type 2 diabetes and related conditions. 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. Even in lean women, insulin resistance can be present, so checking metabolic health is useful regardless of body size. Where insulin resistance is a driver, reducing it directly improves the condition: 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 lowers the insulin load of meals and frequently improves periods, ovulation and androgen symptoms. Try this as a starting point and adjust based on how you feel. Where there is excess weight, even modest loss (around 5 to 10%) can restore ovulation, but 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 minutes of moderate activity a week, plus 2 to 3 resistance sessions of 20 to 30 minutes 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

• Myo-inositol (often 2 g twice daily) has evidence for improving insulin sensitivity and ovulation; discuss with your clinician, especially if trying to conceive.
• If a blood test shows low vitamin D, correcting it may help; routine high-dose supplementation without testing isn’t recommended.
• 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; it is often considered for women with a raised BMI, alongside lifestyle change.
• GLP-1 receptor agonists (weight-loss medicines) may be considered when lifestyle and other treatments aren’t enough; they require medical supervision and reliable contraception, and must be stopped before trying to conceive.
• The combined contraceptive pill is used to regulate periods and reduce androgen symptoms (when not trying to conceive).
• Anti-androgen medicines (such as spironolactone) can help hair and acne but must not be used in pregnancy; reliable contraception is needed if taking them.
• Screening and managing the metabolic risks (blood sugar, blood fats, blood pressure) is part of long-term care.

These options are summaries for understanding; decisions and prescriptions rest with your clinician.

Complications and outlook

PMOS is linked to higher long-term risk of heart and blood vessel disease, partly via insulin resistance, blood fats, and blood pressure. There is also greater risk of type 2 diabetes, gestational diabetes, and fatty liver. So, alongside an annual HbA1c (blood sugar) test, clinicians often check blood fats and blood pressure. Mood and quality of life are commonly affected.

The outlook can be positive. Because insulin resistance is central, 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/HbA1c, blood fats, and blood pressure).
• If you plan pregnancy, ask for a pre-conception review to optimise medications, supplements, and metabolic health beforehand.

Summary