Polycystic ovary syndrome (PCOS) is a common hormonal condition in which the ovaries produce higher-than-normal levels of androgens (male hormones). This hormonal imbalance can disrupt regular ovulation, leading to irregular periods, and can also cause visible symptoms such as excess hair growth, acne and, in some women, thinning scalp hair.
Despite its name, PCOS does not require the presence of actual cysts on the ovaries. What ultrasound often shows in PCOS are numerous small, immature follicles that have not developed and released an egg as they normally would — a pattern sometimes described as "polycystic ovaries," but which is really a sign of irregular ovulation rather than true cysts.
Causes of PCOS
The exact cause of PCOS is not fully understood, but it is believed to result from a combination of genetic and hormonal factors that interact with one another, often reinforcing each other in a cycle that sustains the condition.
- Genetics and family history: PCOS tends to run in families, suggesting a genetic predisposition. Having a mother or sister with PCOS increases the likelihood of developing the condition.
- Elevated androgen levels: Many women with PCOS have ovaries that produce excess androgens. High androgen levels can prevent the ovaries from releasing an egg each month (ovulation), leading to irregular cycles, and are also responsible for symptoms such as excess hair growth and acne.
- Insulin resistance: A large proportion of women with PCOS have insulin resistance, meaning their body's cells do not respond normally to insulin. To compensate, the body produces more insulin, and elevated insulin levels are thought to further stimulate the ovaries to produce more androgens — creating a self-reinforcing cycle that worsens both the metabolic and hormonal features of PCOS.
- Low-grade inflammation: Women with PCOS often have markers of chronic, low-grade inflammation, which research suggests may also stimulate androgen production by the ovaries.
- Weight and metabolic factors: Weight gain, particularly around the abdomen, can worsen insulin resistance and androgen levels, while the hormonal changes of PCOS can in turn make weight management more difficult — meaning weight and PCOS often influence each other in both directions.
Symptoms of PCOS
PCOS symptoms vary considerably between individuals in type and severity. Some women have mild, easily overlooked symptoms, while others experience symptoms that significantly affect daily life, fertility and self-confidence. Symptoms typically begin around puberty but may only become noticeable, or be recognised as PCOS, years later.
Reproductive & Menstrual Symptoms
- Irregular periods — cycles that are infrequent, unpredictable, unusually long, or absent altogether, due to irregular or absent ovulation
- Heavy menstrual bleeding when periods do occur, sometimes related to a thickened uterine lining building up between infrequent periods
- Difficulty conceiving, due to irregular or absent ovulation
- Multiple small follicles on the ovaries, visible on ultrasound
Skin & Hair Symptoms
- Excess hair growth (hirsutism) on the face, chest, back or abdomen, driven by elevated androgen levels
- Persistent acne on the face, chest or back that may extend beyond the teenage years and be resistant to standard treatment
- Thinning hair or male-pattern hair loss on the scalp
- Patches of dark, thickened skin (acanthosis nigricans), typically in body folds such as the neck, armpits, groin or under the breasts — often a sign of underlying insulin resistance
- Skin tags, particularly in areas of skin friction
Metabolic & General Symptoms
- Weight gain or difficulty losing weight, particularly around the abdomen
- Fatigue and low energy
- Sleep disturbances, including an increased risk of sleep apnoea
- Mood changes, including a higher likelihood of anxiety or low mood, which are increasingly recognised as a core part of PCOS rather than a separate issue
It is worth emphasising that PCOS looks different from woman to woman — you do not need to have every symptom, or visible cysts on ultrasound, to have PCOS. Any pattern of irregular periods, unexplained excess hair growth or acne, or difficulty conceiving is a reasonable and valid reason to seek medical advice.
Risk Factors for PCOS
While PCOS can affect any woman of reproductive age, certain factors are associated with a higher likelihood of developing the condition or experiencing more pronounced symptoms:
- Family history: Having a mother, sister or other close female relative with PCOS significantly increases the likelihood of developing the condition.
- Obesity and weight distribution: Both being overweight and having a tendency toward central (abdominal) weight gain are strongly linked to PCOS and can worsen its hormonal and metabolic features, although PCOS also occurs in women of normal weight.
- Insulin resistance: Reduced sensitivity to insulin, whether related to weight, genetics or other factors, is closely tied to the development and severity of PCOS.
- Family history of type 2 diabetes: A personal or family history of type 2 diabetes increases the likelihood of insulin resistance and PCOS.
- Age: Because PCOS-related hormonal changes typically begin around puberty, symptoms often first appear or are first noticed in the teenage and young adult years.
Possible Complications of PCOS
Left unmanaged, PCOS can be associated with several longer-term health complications extending well beyond fertility and menstrual symptoms:
- Infertility or subfertility, due to irregular or absent ovulation — PCOS is the most common cause of anovulatory infertility
- Type 2 diabetes — insulin resistance means women with PCOS have a substantially higher lifetime risk of developing type 2 diabetes, often at a younger age than the general population
- Unfavourable cholesterol levels, including higher LDL ("bad") cholesterol and lower HDL ("good") cholesterol, which raise cardiovascular risk
- High blood pressure, particularly with increasing age
- Increased long-term risk of cardiovascular disease, including heart attack, related to the combined effect of insulin resistance, cholesterol changes and weight
- Endometrial (uterine lining) thickening and, if periods are infrequent over many years without treatment, an increased risk of endometrial cancer
- Pregnancy-related complications, including gestational diabetes, pre-eclampsia and higher rates of miscarriage and preterm birth
- Non-alcoholic fatty liver disease, which is more common in women with PCOS, particularly those with obesity or insulin resistance
- Obstructive sleep apnoea, more common in women with PCOS independent of body weight
- Anxiety, depression and reduced quality of life, which are now recognised as core features of PCOS rather than incidental to it
How PCOS is Diagnosed
There is no single test for PCOS. Diagnosis is based on international, evidence-based criteria (the Rotterdam criteria), which require at least two of three key features to be present, after other conditions that can mimic PCOS — such as thyroid disorders or elevated prolactin — have been ruled out.
- Clinical History & Examination: A detailed discussion of menstrual pattern, weight history, family history, and a physical examination for signs of excess androgen such as acne, hirsutism or hair thinning.
- Blood Tests: Measure androgen and other reproductive hormone levels to assess for biochemical hyperandrogenism, and to help exclude other causes of similar symptoms, such as thyroid disease or elevated prolactin. Blood glucose, insulin and cholesterol levels are also typically checked to assess metabolic health.
- Pelvic Ultrasound: Used to assess ovarian size and the number of small follicles present (polycystic ovarian morphology), and to check the thickness of the uterine lining (endometrium). Not always required for diagnosis — for example, when irregular periods and clinical signs of excess androgen are already present.
- Anti-Müllerian Hormone (AMH): A blood test that can now be used as an alternative to ultrasound to help assess ovarian follicle activity, particularly useful when ultrasound is impractical or inconclusive.
- Assessment for the Three Rotterdam Criteria: A diagnosis of PCOS requires at least two of the following three features: irregular or absent ovulation, clinical or blood-test evidence of excess androgen, and polycystic ovaries on ultrasound (or elevated AMH) — after other causes have been excluded.
If you are trying to conceive and have PCOS, you can work with your healthcare provider for treatment options.
Living with PCOS
Alongside any medical treatment, a number of everyday measures can help manage symptoms and reduce long-term health risks associated with PCOS:
- Focus on a balanced, lower-glycaemic diet: A balanced diet with adequate fibre and protein, moderate refined carbohydrates and added sugar, can help manage insulin resistance and support a healthy weight.
- Stay physically active: Regular aerobic and resistance exercise improves insulin sensitivity, supports weight management, and has been shown to improve mood and menstrual regularity in women with PCOS.
- Aim for gradual, sustainable weight change if overweight: Even modest, gradual weight loss can meaningfully improve hormonal balance, restore more regular ovulation and reduce metabolic risk — the goal is sustainable change rather than rapid weight loss.
- Prioritise sleep and manage stress: Regular sleep and stress-management practices can help support hormonal balance, as poor sleep and chronic stress are both linked to worsening insulin resistance.
- Look after your mental health: PCOS can affect self-esteem and mental wellbeing; seeking support from a counsellor, support group or mental health professional is a valid and valuable part of managing the condition.
- Keep up with regular health screening: Regular blood glucose, cholesterol and blood pressure checks allow early detection and management of the metabolic and cardiovascular risks associated with PCOS.
- Plan ahead if you are trying to conceive: If you are trying to conceive, early discussion with a specialist can help identify the most suitable options and avoid unnecessary delay, given that ovulation issues are often very treatable.
