Polycystic ovary syndrome (PCOS): symptoms, diagnosis and what is known to help

Polycystic ovary syndrome, PCOS, is almost always poorly explained. It gets summed up as «I have cysts on my ovaries» when in fact it is a hormonal disorder in which higher than normal levels of androgens cause irregular periods, abnormal ovulation, infertility, excess facial or body hair and/or acne, according to the World Health Organization fact sheet. Nor is it a passing problem of youth: the WHO describes it as a chronic metabolic condition that persists beyond the reproductive years. That changes the conversation quite a lot.

What PCOS really is

PCOS is a common hormonal disorder. The WHO defines it by excess androgens and their clinical consequences: irregular periods, abnormal ovulation, difficulty getting pregnant, hirsutism (hair growth in a male pattern) and acne. Not all women with PCOS have all of these features, and that is where part of the diagnostic muddle begins: the WHO notes that the syndrome runs in families but shows up very differently from one woman to another. Two sisters with PCOS can have presentations that look nothing alike.

The word «polycystic» is an inherited and unfortunate name, because it draws attention to the appearance of the ovary when the problem is hormonal and metabolic. So much so that in May 2026 a consensus of 56 academic, clinical and patient organisations, published in The Lancet, settled on a new name: PMOS, polyendocrine metabolic ovarian syndrome, which removes the cysts from the name and will be introduced with a transition period. As for the precise pathophysiology (how insulin, androgens and follicle development are linked), the WHO is clear: the cause of PCOS is unknown, although the risk is higher in women with a family history of PCOS or type 2 diabetes.

The uncomfortable figure: up to 70% undiagnosed

According to the WHO, up to 70% of women affected by PCOS are undiagnosed. That is an enormous figure for a condition which, with an estimated prevalence of 10–13% in women of reproductive age, is one of the most common seen in gynaecology and endocrinology clinics. A note of transparency is in order: that prevalence figure also circulates in versions such as 8–13%, likewise attributed to the WHO, and the fact sheet is updated, so take it as an order of magnitude rather than a number set in stone.

The 2023 international guideline points in the same direction: the diagnosis of PCOS is still delayed, the needs of people with PCOS are not adequately met and gaps persist between what the evidence says and what happens in clinical practice. In other words, the problem is not a lack of knowledge; it is that this knowledge takes years to reach the consulting room and the patient.

How it is diagnosed

The diagnosis of PCOS is clinical and rests on a combination of irregular periods or lack of ovulation, signs of androgen excess (clinical or on blood tests) and assessment of the ovaries, as well as ruling out other causes that produce similar pictures. The current international reference for assessment and management is the 2023 international evidence-based guideline, published in the European Journal of Endocrinology.

One detail explains why that guideline matters so much: its 2018 version was independently rated as high quality, brought together multidisciplinary and patient perspectives from 6 continents and is used in 196 countries. Above all, it moved from consensus-based to evidence-based diagnostic criteria, which improved diagnostic accuracy and consistency of care. Previously, much of the diagnosis depended on agreement between experts; now there is more empirical ground underneath it.

According to the WHO, the diagnosis requires at least two of these three features, once other causes have been ruled out: signs or symptoms of androgen excess, irregular or absent periods and polycystic ovaries on ultrasound. The 2023 guideline simplified the diagnostic algorithm and accepts, in adults only, anti-Müllerian hormone as an alternative to ultrasound. The specific thresholds (follicle counts, ovarian volume, anti-Müllerian hormone values or specific time windows in adolescents) are applied by the specialist using the full guideline. What is solid is this: PCOS is not diagnosed with a single blood test or with a stand-alone ultrasound interpreted out of context. It needs a medical assessment of the whole picture.

The metabolic dimension: why it is not «just» gynaecological

The WHO is explicit: PCOS is a chronic metabolic condition that persists beyond the reproductive years. This has a practical consequence for anyone who has it: follow-up does not end once a wish to become pregnant has been resolved or when periods become regular with treatment. Metabolic health is still there, and in many women with PCOS it is the part that carries the most weight in the medium and long term.

The WHO lists the health problems that are more likely with PCOS: type 2 diabetes, high blood pressure, high cholesterol, cardiovascular disease, obesity, sleep apnoea, metabolic steatohepatitis and endometrial hyperplasia or cancer, as well as diabetes or high blood pressure during pregnancy; the 2023 guideline also strengthens recognition of metabolic risk factors, cardiovascular disease and sleep apnoea. That is why, if you recognise yourself in this profile, it makes sense to understand the metabolic conditions with which PCOS shares ground: you can read our explanation of metabolic syndrome and how it is managed, the guide on prediabetes: what it is and how it is managed and what we know about metabolic fatty liver disease. They are pieces of the same board, and discussing them with your doctor helps ensure that follow-up is not limited to the menstrual calendar.

What is known to help (and what we cannot claim)

This is where honesty comes first. The 2023 update strengthens its recommendations compared with the previous version, but its authors make it clear that the quality of the evidence is still generally low to moderate and that much more research is needed. That means there is no strong certainty about quite a few specific interventions, even though they are sold online as absolute certainties.

That is why, in this article, we will not attribute efficacy percentages to any treatment, nor present as indicated for PCOS any medicines whose authorisation in Spain we have not checked against the summary of product characteristics: some of the medicines commonly used in PCOS may be used outside their authorised indication (off-label use), and that is an individual medical decision, with its own legal framework, not something to be chosen by reading an article. Nor can we attribute therapeutic properties to inositol: in Spain it is marketed as a food supplement, not as a medicine.

And two myths worth defusing with what we do know. First: there is no basis for saying that PCOS disappears on a keto, gluten-free or dairy-free diet; PCOS is, in the WHO's words, a chronic condition, and what can be done is to improve its symptoms. Second: the contraceptive pill does not make PCOS go away (it can manage symptoms while it is being taken), and the idea that it causes infertility later on is not supported. The realistic approach combines managing the symptoms that bother each woman most with looking after metabolic health over time.

In summary, and what you can do today

What to remember: PCOS is common, it is chronic and metabolic, and up to 70% of affected women remain undiagnosed, largely because the evidence is slow to reach practice. The sooner it is named, the sooner you can look after what can be looked after. If weight is one of the pieces of your metabolic health, what does exist today in Spain is medical weight-loss treatment, with a prior assessment, a prescription when appropriate from a registered doctor and ongoing follow-up. If you recognise yourself in this article, you can see whether the treatment suits your case.