What Is PCOS (PMOS)? A Clear Explanation of Symptoms, Causes and Diagnosis

‍Medically reviewed by Puja Vyas, Lead Clinical Pharmacist.

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PCOS in a Sentence

PCOS or polycystic ovary syndrome is a common hormonal condition that affects 1 in 8-10 women of reproductive age. It causes irregular or absent periods, higher-than-normal levels of male-type hormones, and sometimes small fluid-filled sacs on the ovaries. It affects metabolism, weight, skin, hair, mood, and fertility.

While PCOS is a fairly common term, many women are still unclear of what it actually means, and how it affects the body. We’ve written this article especially for them. No jargon. No assumptions. Just a plain explanation of what PCOS is, what causes it, what it feels like, and what can be done about it.

Key Takeaways

• PCOS stands for polycystic ovary syndrome. It affects roughly 1 in 8 to 10 women and is one of the most common hormonal conditions in women of reproductive age
• In 2026, PCOS was officially renamed PMOS (polyendocrine metabolic ovarian syndrome) by a global panel of medical experts. The condition is the same, only the name changed
• PCOS and PCOD are often used interchangeably, but they are not the same thing. PCOD is a milder, more common condition; PCOS involves a more significant hormonal imbalance
• It is caused by a combination of hormonal disruption, insulin resistance, and genetics
• Symptoms range from irregular periods and acne to weight changes, hair loss, and low mood
• It cannot be cured, but it is very manageable with the right approach

What Does PCOS Stand For, and What Is PMOS?

PCOS stands for polycystic ovary syndrome. ‘Polycystic’ means ‘many cysts.’ Many women with the condition develop multiple small, undeveloped egg follicles that look like tiny cysts on an ultrasound. This is where the name comes from.

However, the name is kind of misleading. The follicles are not really cysts, they are simply eggs that haven't matured and released properly. And the ovaries are only one part of a much bigger hormonal picture. This is exactly why the name was changed in 2026.

Why PCOS Was Renamed PMOS in 2026

In May 2026, after 14 years of international research and input from over 22,000 patients and healthcare professionals across 56 organisations worldwide, a landmark paper published in The Lancet officially renamed the condition PMOS: polyendocrine metabolic ovarian syndrome.

The new name tells the PCOS story more accurately:

• Polyendocrine: the condition involves multiple hormones going out of balance, not just one
• Metabolic: it affects metabolism, blood sugar, weight, and cardiovascular health, not just the reproductive system
• Ovarian: the ovaries are still central to the condition, but no longer the whole story

Note that if you were diagnosed with PCOS before this name change, your diagnosis doesn’t change. It’s just the name that has changed, not the criteria or the treatment.

Here’s an entire article on why the name change if you’re curious: PCOS renamed PMOS: what it means and why it matters →

Is PCOS the Same as PCOD?

No. While they are related, they are not the same.

• PCOD (polycystic ovarian disease): It is a condition where the ovaries produce immature eggs, which can cause irregular periods and some hormonal symptoms. It is more common, and generally milder. Lifestyle changes usually work on it.
• PCOS (polycystic ovary syndrome): It involves a more significant hormonal imbalance, including elevated androgens (male-type hormones) and often insulin resistance. It has wider effects on metabolism, weight, fertility, and long-term health

You may see very similar symptoms in both, and which is why they are often used interchangeably. But PCOS requires a more active management as its diagnostic framework is more specific.

What Causes PCOS?

There is no single cause. PCOS develops from a combination of hormonal imbalance, the way your body handles insulin, and your genetics. All three working together.

The Hormonal Imbalance Behind PCOS

Your brain sends signals to the ovaries to grow and release an egg each month. This requires a careful balance of hormones working in sequence. PCOS occurs when this balance is disrupted.

The ovaries produce too much testosterone and other male-type hormones (androgens). This excess androgen interferes with normal egg development, which prevents the eggs from maturing and being released. Without ovulation, the regular cycle of progesterone and shedding does not happen, and periods become irregular or stop.

The Role of Insulin Resistance

70 to 80% of women with PCOS suffer from insulin resistance. This means that while their body produces insulin normally, their cells do not respond to it. When this happens, the body compensates by making more and more insulin. These elevated levels then stimulate the ovaries to produce even more androgens, making the hormonal imbalance worse.

It forms a loop: more insulin -> more androgens -> disrupted ovulation -> low progesterone -> effects on how the body processes glucose and stores fat. This is why PCOS often makes weight management much harder than expected.

Here’s an entire article if you’re curious: PCOS and insulin resistance: what’s the connection and what helps →

And another: PCOS and weight loss: what actually helps →

Is PCOS Genetic?

Yes. If your mother, sister, or another close female relative has PCOS, you are more likely to have it too. Although the condition is not caused by a single gene, genetics does play a meaningful role in it. Environmental and lifestyle factors influence how strongly those genes express themselves.

Common Symptoms of PCOS

PCOS often looks different for every woman suffering from it. You may have seen some women have several of these symptoms and some others just one or two. But it is important to know that having fewer symptoms does not mean that the condition is less serious.

Physical Symptoms

• Acne, particularly along the jaw, chin, and lower face
• Excess hair on the face, chest, or abdomen (this is called hirsutism)
• Scalp hair thinning, especially at the crown and central parting
• Oily skin
• Weight gain, particularly around the middle
• Darker patches of skin in areas like the neck, armpits, or groin (a sign of insulin resistance)

Here’s an article where we’ve explained PCOS and hair loss in more detail: PCOS and hair loss: causes and treatment options →

Menstrual and Cycle-Related Symptoms

• Irregular periods: cycles that are longer than 35 days, fewer than 8 periods a year, or no periods at all
• Heavy or unpredictable bleeding when periods do arrive
• Pelvic pain or discomfort (reported by around 30% of women with PCOS)
• Difficulty getting pregnant due to irregular or absent ovulation

If you’re suffering from pelvic pain in PCOS, you would like to read: PCOS, periods and pain: what’s normal and what isn’t →

Mood and Mental Health Symptoms

Women with PCOS experience significantly more anxiety, depression, low mood, and body image concerns than women without the condition. These are not tantrums or emotional reactions to a difficult diagnosis. The hormonal and metabolic disruption that PCOS causes, directly affects brain chemistry, including the pathways that regulate mood and energy.

Something worth knowing: PCOS is not a checklist where you need to tick every box to qualify. Many women are told they can't have PCOS because their periods are regular, or their weight is fine, or their blood tests look normal. That is not how the diagnosis works. It requires 2 of 3 specific criteria, and there are many possible combinations.

If something feels off and you have been dismissed, we urge you to push for a proper assessment.

How Common Is PCOS?

PCOS affects roughly 1 in 8 to 10 women of reproductive age. That’s around 170 million people worldwide. The WHO and Lancet have both published figures that match this range.

However, despite being so common, up to 70% of these go undiagnosed. The reasons: symptoms are varied and easy to misattribute, many GPs are not trained to recognise the full metabolic picture, and women are frequently told their symptoms are normal, stress-related, or because of their weight.

The old name, PCOS, caused most cases to be redirected to gynaecologists when the metabolic and hormonal dimensions were equally or more important.

How Is PCOS Diagnosed?

PCOS is diagnosed using the Rotterdam criteria: you must have at least 2 of the following 3 features to qualify.

• Irregular or absent periods
• Signs of too many male-type hormones, either visible on the skin and hair, or confirmed on a blood test
• Polycystic-looking ovaries on ultrasound, or an elevated AMH blood test result

You don’t need to have all three, and you don’t necessarily need an ultrasound. If your periods are irregular and a blood test confirms elevated androgens, that alone meets the threshold.

You can know more about PCOS blood tests, criteria and what to expect at your GP: how is PCOS diagnosed? →

Can PCOS Be Treated?

Not entirely, but it can definitely be managed effectively. This means that most of its symptoms can be significantly reduced or controlled, and the long-term health risks associated with it (type 2 diabetes, cardiovascular disease, endometrial changes) can be meaningfully lowered.

Treatment depends on which aspects of PCOS matter most to you right now. Your options include:

• Lifestyle changes: a low-glycaemic index diet and regular resistance training can directly improve insulin sensitivity, which reduces androgen production and can restore more regular cycles
• Medication: metformin (an insulin-sensitising tablet) is widely used for PCOS in the UK. The combined oral contraceptive pill is often prescribed to regulate periods and reduce androgen symptoms like acne and hair growth
• Weight loss support: for women who are overweight, even a 5% reduction in body weight can restore ovulation and reduce symptoms significantly. GLP-1 medications can support this effectively where eligible

Here are some more related articles we’ve written on this topics if you’re interested to know more –

PCOS diet: what to eat, what to limit: PCOS diet →

PCOS belly fat and bloating: why it happens and what helps →

GLP-1 medications for PCOS: Mounjaro and PCOS: what the evidence says →

If you have PCOS and want to understand your metabolic picture properly: SheMed’s free at-home blood test covers fasting glucose, HbA1c, thyroid, cholesterol, and liver enzymes, reviewed by a clinician before anything is prescribed.

You can start your journey only from £59 for your first month.

Know more →

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Frequently Asked Questions

What does PCOS mean?

PCOS stands for polycystic ovary syndrome. It is a hormonal condition that affects how the ovaries work, causing irregular periods, elevated male-type hormones, and often metabolic changes including insulin resistance.

Is PCOS the same as PCOD?

No. PCOD (polycystic ovarian disease) is a condition where the ovaries produce immature eggs. It is usually milder, and lifestyle changes can improve the symptoms. PCOS involves a more significant hormonal imbalance, including elevated androgens and often insulin resistance, and has wider effects on metabolism, weight, and long-term health. Both conditions look similar but are distinct.

What is the difference between PCOS and PMOS?

PMOS is the new official name for PCOS, agreed in a 2026 Lancet consensus. The condition is entirely the same. The name changed because PCOS, which refers to "polycystic ovaries," was misleading: the follicles are not true cysts, and the ovaries are only one part of a much wider hormonal and metabolic picture. PMOS better reflects that.

Is PCOS a serious condition?

Yes, it is a lifelong hormonal and metabolic condition with real implications for fertility, weight, cardiovascular health, and long-term diabetes risk if unmanaged. With the right support, most women with PCOS manage it effectively and live healthy, full lives.

Can you have PCOS without knowing?

Absolutely, and it is very common. Up to 70% of women with PCOS are estimated to be undiagnosed. Symptoms are often gradual, easy to attribute to other causes (stress, diet, just being your body), and frequently dismissed by GPs who see only one feature rather than the full picture. Many women receive a diagnosis years after symptoms first appeared.

Does PCOS go away?

PCOS does not go away entirely, but the way it shows up changes over time. Reproductive symptoms like irregular periods may ease or shift at perimenopause, but the underlying metabolic features, insulin resistance, cardiovascular risk, and the tendency toward abdominal fat storage, do not resolve. This is why ongoing monitoring and management matter even as you move through different life stages.

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Sources and Further Reading

1. NHS – Polycystic Ovary Syndrome (PCOS) Overview

2. Teede HJ et al. – Polyendocrine Metabolic Ovarian Syndrome, the new name for PCOS. The Lancet. 2026.

3. WHO – Polycystic Ovary Syndrome Fact Sheet

4. NICE CKS – Polycystic Ovary Syndrome

5. Cleveland Clinic – Polycystic Ovary Syndrome (PCOS)

6. Johns Hopkins Medicine – Polycystic Ovary Syndrome (PCOS)

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