PCOS: Polycystic Ovary Syndrome

Polycystic ovary syndrome, or PCOS, is a common hormonal condition that affects how the ovaries work. It often involves irregular periods, signs of higher androgen activity, and changes in the ovaries seen on ultrasound. Because its features vary widely, diagnosis is made by combining symptoms, examination, blood tests, and imaging.

What PCOS is

PCOS is a syndrome, meaning it is defined by a cluster of features rather than a single test result. Several systems can be involved. Ovulation may be irregular or absent, which leads to irregular menstrual cycles. Levels or effects of androgens, sometimes called male-type hormones although they are present in everyone, may be higher than usual. The ovaries may contain many small follicles visible on ultrasound. Many people with PCOS also have differences in how the body handles insulin, the hormone that regulates blood sugar.

Not everyone with PCOS has all of these features, and the balance differs from person to person. This variability is part of why careful evaluation is needed, and why PCOS is recognised by combining several findings rather than by one result.

Common features

Signs typically appear in the teenage years or early adulthood and may include:

• Irregular, infrequent, or absent menstrual periods
• Difficulty becoming pregnant, related to irregular ovulation
• Excess hair growth on the face or body (hirsutism)
• Acne or oily skin
• Thinning of the scalp hair (sometimes in a pattern similar to male-type hair loss)
• Weight gain or difficulty losing weight
• Darkened patches of skin, often in folds such as the neck or armpits (acanthosis nigricans), in some people

These features cluster into a few themes: a problem with regular ovulation, signs of higher androgen activity, and — in many but not all people — metabolic differences. The combination and severity vary widely.

How PCOS can change over time

PCOS is not static. Its features can shift across the years, which is part of why it is followed over time rather than diagnosed once and forgotten. Symptoms such as acne and irregular cycles often draw attention in the teens and twenties. Cycles may become somewhat more regular for some people later, while metabolic considerations such as blood sugar and weight may become more prominent with age. Around the menopausal transition, the picture changes again as ovarian hormone production winds down. Because of this evolving course, the priorities of care — and the features a clinician focuses on — tend to change at different life stages, and ongoing review is the norm.

What causes it

The exact cause of PCOS is not fully understood and remains an area of ongoing research. It appears to involve a mix of genetic and hormonal factors. Differences in how the body responds to insulin are common and may influence androgen activity in the ovaries. PCOS often runs in families, suggesting an inherited component. What is established is that PCOS reflects a disturbance in the normal hormonal signals that govern ovulation, rather than a single, simple cause.

A commonly described picture links several of the features together. When the body is less responsive to insulin, it may produce more insulin to compensate, and higher insulin can encourage the ovaries to make more androgens. Higher androgen activity, in turn, can interfere with the regular maturation and release of eggs, contributing to irregular cycles and the many-follicle appearance on ultrasound. This is a general model rather than a fixed sequence, and the relative importance of each factor differs between individuals, which is one reason the condition looks so different from person to person.

The diagnostic framework

There is no single test for PCOS. Widely used criteria recognise three main components, and a diagnosis is generally based on having a defined combination of them — commonly two of the three — after other conditions that can look similar have been excluded. The three components are:

1. Irregular or absent ovulation, usually showing up as irregular, infrequent, or absent periods.
2. Signs of higher androgen activity, either physical signs such as excess hair growth or acne, or raised androgen levels on a blood test.
3. Polycystic ovary appearance on ultrasound, meaning the ovaries contain many small follicles or are enlarged.

Because two of the three can be enough, the "polycystic" appearance is not always required, and not everyone with the label has ovarian changes on imaging. In adolescents, clinicians are generally more cautious, because some features overlap with normal puberty. The key principle is that PCOS is a diagnosis of combination and exclusion.

This table is illustrative and qualitative. The exact criteria and thresholds vary between guidelines and are applied by a clinician; this is not a self-diagnosis tool.

How it is evaluated

Clinicians generally look for the combination above and exclude other conditions that can mimic it. Evaluation often includes:

• A review of menstrual history and symptoms, plus a physical examination
• Blood tests for androgens, such as testosterone, to assess androgen activity
• Tests to rule out other conditions, including thyroid function (TSH), prolactin, and sometimes other hormones such as those that point to thyroid or adrenal causes
• Markers of blood sugar and insulin handling, such as a glucose measure or a longer-term blood sugar marker, since metabolic differences are commonly involved
• A pelvic ultrasound to look at the ovaries

For background on the individual markers, see our blood tests, hormones, and panels sections.

Related metabolic considerations

PCOS is not only a reproductive condition; for many people it overlaps with how the body handles insulin and blood sugar. Insulin resistance — where the body needs more insulin to achieve the same effect — is commonly seen, and it may interact with androgen activity. Over the longer term, this is why clinicians often pay attention to blood sugar, weight, cholesterol, and blood pressure, and why metabolic health is part of ongoing monitoring. Not everyone with PCOS has these features, and being at a higher weight is not required for the diagnosis. These are general associations, and an individual's picture is interpreted by a clinician.

How it is generally managed

Because PCOS varies so much, management is tailored to the person's symptoms and goals and is decided with a clinician. Rather than a single treatment, care usually targets whichever features matter most to the individual:

• Cycle regularity and the uterine lining: When periods are very infrequent, clinicians may discuss approaches to establish a more regular bleeding pattern and to keep the uterine lining healthy.
• Skin and hair symptoms: Excess hair growth, acne, and scalp hair changes can be addressed with approaches a clinician explains.
• Fertility: When pregnancy is a goal, support for ovulation may be discussed; when it is not, contraception needs are also considered.
• Metabolic health: Blood sugar, weight, cholesterol, and blood pressure may be monitored and addressed over time.

Lifestyle measures are commonly part of the picture and may help several features at once. Because PCOS can have long-term metabolic implications, ongoing monitoring is often recommended even after symptoms are controlled. You can browse related symptoms and general principles in our treatments section, and find related life-stage context under life stages. This page is educational and does not provide personalised advice or dosing.