PCOS Explained: Symptoms, Causes and What Moves the Needle

PCOS is a metabolic and hormonal condition, diagnosed when you meet two of three Rotterdam criteria: irregular ovulation, high androgens, or polycystic ovaries on ultrasound. Insulin resistance drives most cases, which is why the interventions that work are metabolic rather than reproductive. Here is what the evidence supports, and what it does not.

🧬 What PCOS Actually Is

Polycystic ovary syndrome is diagnosed using the Rotterdam criteria, still the international reference point. Two of three findings are enough, and no single test is decisive. Rotterdam ESHRE/ASRM consensus, Human Reproduction, 2004

• Irregular or absent ovulation — cycles longer than 35 days, fewer than eight periods a year, or none at all
• Clinical or biochemical hyperandrogenism — raised testosterone on blood work, or visible signs such as excess facial hair, persistent acne or male-pattern thinning
• Polycystic ovarian morphology — twelve or more follicles of 2–9 mm in one ovary, or ovarian volume above 10 mL

The name misleads. Those follicles are eggs that stalled before maturity, not cysts. Normally one follicle becomes dominant and ovulates; here that selection fails and small follicles accumulate. You can meet the criteria with completely normal ovaries.

What ties the three together is the signalling environment the ovary responds to, not the ovary itself. That is why one diagnosis covers a lean 22-year-old with acne and a 38-year-old with central weight gain and no periods. Christ, Diagnostics, 2023

📋 The Four Phenotypes: Not One Condition

Rotterdam defines the diagnosis; phenotypes describe which version you have. The distinction matters because metabolic risk and treatment priority differ between them. Lizneva, Fertility and Sterility, 2016

Phenotype C is why “but my periods are regular” is not an answer. Phenotype B is why “but my scan was normal” is not one either. Women in both groups get told they do not qualify.

📈 What Causes PCOS? Insulin Resistance and Three Other Drivers

No single cause: a genetic predisposition that needs an environmental push, with four mechanisms doing most of the work.

Insulin resistance is the engine

In the majority of cases insulin resistance is present and upstream of the reproductive symptoms. When muscle, fat and liver respond poorly to insulin, the pancreas releases more. That excess drives ovarian theca cells to produce androgen and suppresses sex hormone-binding globulin, so more testosterone circulates unbound. Zhao, Journal of Ovarian Research, 2023

Hyperinsulinaemia and insulin resistance overlap without being identical, and a woman can have one without the other — which is why a normal fasting insulin does not close the question as neatly as it looks. Houston, Journal of Endocrinology, 2025

The LH/FSH imbalance. The pituitary releases luteinising hormone out of proportion to FSH. High LH pushes theca cells toward androgen production; relative FSH insufficiency means no follicle gets selected to ovulate. Anovulation then removes the progesterone that would reset the cycle, so the pattern sustains itself. Chan, Journal of Clinical Investigation, 2026

Low-grade inflammation. PCOS has been described as a systemic inflammatory endocrinopathy, with C-reactive protein and interleukin-6 raised even in women of normal weight. Inflammation impairs insulin signalling and insulin resistance promotes inflammation, so the loop runs both ways — the rationale for testing anti-inflammatory eating patterns at all. Patel, Journal of Steroid Biochemistry and Molecular Biology, 2018

Genetics. PCOS clusters in families, and first-degree relatives carry higher rates of both PCOS and metabolic syndrome, so family history belongs in the assessment. The case for chronic inflammation runs through the same biology.

⚡ Symptoms: More Than Irregular Periods

Two women with the same diagnosis can share almost no symptoms. The common threads:

• Menstrual irregularity — cycles over 35 days, fewer than eight periods a year, or cycles that stop
• Hirsutism — coarse hair on the face, chin, chest or abdomen, in a male pattern
• Acne and oily skin — often along the jaw, often resistant to topical treatment
• Androgenic alopecia — thinning at the crown and temples, frequently dismissed as stress
• Central weight gain — abdominal fat driven by insulin signalling, not discipline
• Fertility difficulty — anovulation makes conception unpredictable, not impossible
• Mood and cognition — higher rates of anxiety and depression, and brain fog that tracks blood sugar

Hair thinning and mood are the two missed most often.

🔍 Why Does Diagnosis Take So Long?

The criteria are clear. The route to them is not, and four failures account for most of the delay.

• Adolescent cycles are waved through. Irregularity is normal after menarche, but persistent anovulation beyond that is a finding, not a phase
• The scan is treated as the test. Follicle counts vary with technique and with who reads the image, so a normal report does not exclude PCOS
• Weight is treated as the diagnosis. Being told to lose weight is not a workup, and it delays the metabolic assessment
• Other causes are not excluded. Thyroid dysfunction, high prolactin and non-classic adrenal hyperplasia all mimic parts of the picture

Guidance is explicit that PCOS is a diagnosis of exclusion as well as inclusion, so the tests ruling other conditions out are part of the diagnosis, not an extra. (Christ, Diagnostics, 2023)

⚠️ The Long-Term Risks People Are Not Told

The reproductive symptoms get the appointment; the metabolic and endometrial consequences get a paragraph, if that. The consensus that defines the diagnosis also sets out the long-term risks, which is why PCOS is something to monitor, not endure. (Rotterdam consensus, Human Reproduction, 2004)

🏃 What Actually Moves the Needle?

Four interventions have meaningful human evidence. None is novel, and none is sold as a protocol.

Weight, with two corrections. Structured diet and exercise improve insulin sensitivity, cycle regularity and androgen measures, and the effect appears with modest loss rather than a target BMI. Gautam, Nutrients, 2025 PCOS makes weight loss harder, because insulin resistance drives fat storage and hunger, so willpower framing is both wrong and counterproductive. Lean PCOS is also real: a normal BMI does not rule out insulin resistance, which is why tracking glucose response says more than the scale.

Sleep timing, not sleep perfection. The evidence is thin: no trial of sleep extension in PCOS justifies a symptom claim. What is defensible is narrower. Sleep timing anchors the rest of the plan, and a consistent wake time survives a bad night.

• Fix the wake time first — it sets circadian timing and holds better than a fixed bedtime
• Get outdoor light early — the strongest available signal for shifting timing earlier
• Protect the last hour — dim light and no screens beats most sleep supplements

Timing matters more than hours in bed (sleep architecture), and CBT-I is first-line if sleep has become the problem.

Resistance training beats another hour of cardio

Muscle is the largest glucose sink, so building it changes insulin sensitivity in a way cardio alone does not.

• Two or three sessions a week — compound movements, progressive load, enough protein to support the adaptation
• A ten to fifteen minute walk after meals — the cheapest way to blunt a post-meal glucose rise
• Yoga once or twice a week — modest but consistent evidence for yoga on anxiety and androgen measures, with better adherence than most programmes

The highest-burn exercises are rarely the ones people keep doing.

Inositol: the best-studied supplement

Myo-inositol has more randomised evidence in PCOS than anything else on the shelf. A meta-analysis of controlled trials found improvements in ovulation and metabolic parameters, with the usual caveat: the trials were small and heterogeneous. Unfer, Endocrine Connections, 2017

Two details decide whether a product is the thing that was studied. The ratio matters: most protocols use 40:1 myo-inositol to D-chiro-inositol, and a tub that does not state its ratio is not that formulation. The comparator matters too, and a trial comparing myo-inositol plus metformin against metformin alone answers a more useful question than another placebo comparison. Nazirudeen, Clinical Endocrinology, 2023 Read that one yourself rather than trusting a summary, including this one.

💊 Do Supplements Help PCOS?

Some do something. None replaces the four interventions above, and the review literature is blunt about quality: many small trials, inconsistent doses, few measuring an outcome anyone would notice. Alesi, Advances in Nutrition, 2022

• Vitamin D — deficiency is common in PCOS and correcting a low level is reasonable; it is not a stand-alone treatment. Test first; see what a deficiency looks like
• Omega-3 — small trials, modest effects on triglycerides and androgen measures; not worth an expensive dose
• Probiotics and prebiotics — early signals from small studies with inconsistent designs; promising is not proven Martinez Guevara, Nutrients, 2024
• Anything sold as a hormone balancer — if the label names no compound, dose and ratio, there is nothing to evaluate
• Third-party testing — the market is not reliably policed, so a batch certificate from an accredited lab is the minimum

🩺 Medical Treatment: What Is Available

Medical treatment has two jobs: manage symptoms while lifestyle changes take effect, and address specific goals such as fertility or endometrial protection. Whether you are trying to conceive reorders the list. (Chan, Journal of Clinical Investigation, 2026)

• Combined hormonal contraception — first-line for acne, hirsutism and cycle regulation when conception is not the goal; it suppresses ovarian androgen production and raises binding globulin
• Metformin — an insulin sensitiser used off-label, with the strongest rationale in impaired glucose tolerance; extended-release forms reduce gastrointestinal effects
• Letrozole — ovulation induction, and now the usual first choice ahead of clomiphene for women trying to conceive
• Anti-androgens — spironolactone for hirsutism and acne when contraception is in place, since it is not safe in pregnancy

What is missing from most consultations is sequencing: which problem is treated first, what the endpoint looks like, and when to stop. A plan without a review date is not a plan.