PCOS (Polycystic Ovary Syndrome)

What it is

PCOS is a common hormonal and metabolic disorder affecting about 10–13% of reproductive-aged women worldwide. It is defined by a pattern of irregular or absent ovulation, signs of excess androgens such as acne or excess facial hair, and sometimes polycystic-appearing ovaries on ultrasound. The name can be misleading because not everyone with PCOS has ovarian cysts, and the condition is not diagnosed by ultrasound alone. PCOS is also called polycystic ovary syndrome, and older terms such as PCOD or polycystic ovarian disease are still used, but current medical guidance generally uses PCOS.

PCOS is one of the most common causes of anovulation and infertility. It can begin in adolescence, but diagnosis is often delayed because symptoms overlap with normal puberty, stress-related cycle changes, thyroid disease, high prolactin, and other conditions. Beyond periods and fertility, PCOS is linked with insulin resistance, weight gain in some people, type 2 diabetes risk, fatty liver disease, sleep apnea, and anxiety or depression. WHO notes that many affected women remain undiagnosed.

A simple way to think about PCOS is that it affects both reproductive hormones and metabolism. Symptoms vary widely. Some people have obesity, while others have "lean PCOS" and still have insulin resistance or androgen excess.

Common features of PCOS	Examples
Menstrual or ovulation problems	Infrequent periods, absent periods, difficulty conceiving
Hyperandrogenism	Hirsutism, acne, scalp hair thinning
Metabolic features	Insulin resistance, weight gain, prediabetes
Ovarian findings	Multiple small follicles on ultrasound in some patients

How it works

PCOS does not have one single cause. It is thought to result from a mix of genetic susceptibility, insulin resistance, altered ovarian hormone production, and brain-ovary signaling changes. Many patients have higher insulin levels, and insulin can stimulate the ovaries to make more androgens. Higher androgen levels can then interfere with normal follicle development and ovulation, leading to irregular cycles.

Hormone signaling is often altered in the hypothalamic-pituitary-ovarian axis. Luteinizing hormone may be relatively increased, which can further promote ovarian androgen production. At the same time, ovulation may not occur regularly, so progesterone exposure is reduced. This matters because prolonged irregular cycles can leave the uterine lining exposed to estrogen without regular progesterone withdrawal, which can raise the risk of endometrial hyperplasia over time.

Body weight can worsen symptoms in some people, but PCOS is not simply a consequence of obesity. People with normal body weight can also have PCOS. Fat distribution, especially visceral adiposity, appears to matter metabolically. Family history is common, supporting a genetic component.

Diagnosis / how it's measured

PCOS is a clinical diagnosis supported by history, examination, lab tests, and sometimes ultrasound. There is no single blood test that confirms it. In adults, many clinicians use the Rotterdam criteria, which require 2 of the following 3 after excluding other causes:

1. Irregular or absent ovulation
2. Clinical or biochemical hyperandrogenism
3. Polycystic ovarian morphology on ultrasound

Doctors usually also check for conditions that can mimic PCOS, such as:

• Thyroid disease
• Hyperprolactinemia
• Nonclassic congenital adrenal hyperplasia
• Cushing syndrome in selected cases
• Androgen-secreting tumors if symptoms are severe or rapidly progressive

Typical evaluation may include menstrual history, acne or hirsutism assessment, weight and waist measures, blood pressure, total or free testosterone, prolactin, thyroid-stimulating hormone, glucose testing, and lipid profile. Depending on the case, clinicians may use an oral glucose tolerance test because fasting glucose alone can miss dysglycemia.

In adolescents, diagnosis is more cautious because irregular cycles and acne can be common in normal puberty. Ultrasound is less helpful early after menarche, so persistent ovulatory dysfunction and evidence of androgen excess are more important.

In India, PCOS is a common reason for gynecology and infertility visits, and clinicians often also assess diet pattern, physical activity, sleep, and diabetes risk because South Asian populations may develop metabolic complications at lower body mass indices than some Western populations.

Evidence and uses

Management depends on the person's main goals: cycle control, acne or hirsutism treatment, fertility, or metabolic risk reduction. There is no cure, but symptoms and long-term risks can often be improved.

Goal	Common evidence-based approaches
Irregular periods	Lifestyle measures, combined oral contraceptives, cyclic progestin in selected patients
Acne or hirsutism	Combined oral contraceptives; anti-androgen therapy in selected cases with contraception
Insulin resistance or prediabetes	Weight loss if indicated, exercise, metformin in selected patients
Infertility due to anovulation	Ovulation induction, often with letrozole as first-line in many guidelines

Lifestyle treatment is a core part of care. For people with excess weight, even modest weight loss can improve ovulation and metabolic markers. Regular exercise and a sustainable eating pattern can help even without major weight loss. There is no single "PCOS diet" proven best for everyone.

For menstrual irregularity and androgen-related symptoms, combined oral contraceptives are commonly used if pregnancy is not desired. Metformin is often used when insulin resistance, prediabetes, or type 2 diabetes risk is a concern, and it may also help cycle regularity in some patients. For infertility related to anovulation, letrozole is widely used as first-line ovulation induction.

PCOS also requires screening beyond reproductive symptoms. Patients have higher rates of impaired glucose tolerance, type 2 diabetes, dyslipidemia, obstructive sleep apnea, and mental health symptoms. Endometrial protection is important in those with prolonged infrequent bleeding.

When to see a clinician

See a clinician if periods are consistently irregular, absent for more than 3 months when not pregnant, or very heavy; if there is new excess facial or body hair, severe acne, or scalp hair thinning; or if pregnancy has not occurred after trying to conceive. Medical review is also important for rapid onset virilization, such as deepening voice or marked muscle gain, because that can suggest a different and more urgent cause.

People already diagnosed with PCOS should have periodic follow-up for blood pressure, glucose status, lipids, weight trend, and mental health. Seek care sooner for symptoms of diabetes, abnormal uterine bleeding, or sleep apnea. Adolescents with persistent cycle irregularity more than 2 years after menarche should also be evaluated rather than assuming it is normal puberty.

Limitations and open questions

PCOS is heterogeneous, which means two people with the same diagnosis may have very different symptoms and risks. Diagnostic criteria differ across studies, so prevalence estimates vary. Evidence is strong for lifestyle measures, hormonal treatment for symptom control, and ovulation induction for infertility, but there is still debate about the best way to classify PCOS subtypes and predict long-term outcomes.

Research is ongoing on lean PCOS, the role of gut microbiome changes, inflammation, and newer metabolic drugs. Evidence for many supplements promoted for PCOS, such as inositols or herbal products, is mixed or still emerging. Some may help selected patients, but product quality and study quality vary. Patients should discuss supplements with a clinician or pharmacist because interactions, pregnancy plans, and delayed diagnosis of other conditions are real concerns.

The older term PCOD is still widely used in public discussion, especially in South Asia, but it is not a separate modern diagnosis in most current guidelines. Using the term PCOS helps align care with current evidence and screening for both reproductive and metabolic health.