A chapter of The Invisible Fire

PCOS → PMOS.

Polycystic ovary syndrome is one of the most common hormonal conditions in women — up to one in eight — and one of the most metabolically misunderstood. It is filed as a reproductive problem, treated largely through the reproductive system, and yet for a great many women its root is the same fire that runs through this whole series: high insulin, acting on the ovary. In 2026 the condition was officially renamed to say exactly that.

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Named for the ovaries, driven from elsewhere

The organ where the symptoms show isn't where it starts.

The name points at the ovaries — "polycystic" — and the ovaries are where the visible signs appear: irregular or absent periods, difficulty conceiving, the effects of excess male hormones. But for a large share of women, the ovary is not where the problem starts. It is downstream of a metabolic signal, and naming the condition after the organ where the symptoms show has quietly obscured the driver — exactly the pattern this series keeps meeting.

High insulin does two things at once: it drives the ovary to make more androgens, and it lowers the carrier that would keep them in check.
For education only. Not medical advice. PCOS is a medical diagnosis with real consequences for health and fertility, and this chapter is not a diagnosis, a treatment plan, or fertility advice. Nothing here is a reason to start or stop any medication. Assessment and management belong with a doctor who knows you.
The name just changed

And it changed toward the metabolic.

In May 2026, after more than a decade of international consensus-building, polycystic ovary syndrome was officially renamed. The new name is Polyendocrine Metabolic Ovarian Syndrome — PMOS. A single letter changes in the acronym, C to M, but the shift it marks is exactly the one this chapter is about.[5]

Two problems drove the change. First, the old name was simply inaccurate: "polycystic" points at ovarian cysts, but the structures seen on a scan are follicles, not cysts, and many women with the condition have none at all — a misnomer that helped leave the majority of cases undiagnosed. Second, and more important here, naming the condition after the ovary localised it to the wrong organ. The renaming consortium — led by Professor Helena Teede, who also chaired the 2023 international guideline cited throughout this piece — deliberately moved the name away from the ovary and toward the two words that carry the real weight: polyendocrine (hormonal, across several systems) and metabolic.

The field named the root. The new name leads with "metabolic" — the argument of this whole chapter, now written into the name itself.
The consensus stated the reason plainly: the condition carries strong metabolic and cardiometabolic consequences — diabetes and cardiovascular risk — that the old, ovary-focused name obscured, delaying diagnosis and missing early intervention. It is the same move the liver world made when "non-alcoholic fatty liver" became "metabolic dysfunction-associated" disease: the label finally pointing at the driver rather than the organ where the signs show.
Two honest caveats. The diagnostic criteria have not changed — the Rotterdam framework still defines the condition; this is a conceptual and naming shift, not a new test. And adoption is gradual: a three-year education campaign is planned, with full implementation at the 2028 guideline update, so "PCOS" will remain on forms, prescriptions and search engines for years yet. The name has changed; the paperwork will catch up slowly.
Question One
What is PCOS — now PMOS — exactly?

It is diagnosed under the widely-used Rotterdam framework — unchanged by the rename and carried into the 2023 international guideline — when two of three features are present: irregular or absent ovulation; signs of excess androgens (clinical, such as acne or excess hair, or on a blood test); and polycystic-appearing ovaries on a scan.[1] Because only two of three are needed, it is a spectrum, not a single thing: it looks different from woman to woman, which is part of why it's under-diagnosed and often misunderstood.

It is also common and consequential: beyond periods and fertility, PCOS carries raised long-term risk of type 2 diabetes, fatty liver, and the wider metabolic cluster — the first clue that it isn't really a reproductive condition in isolation.

Question Two
How does the fire reach the ovary?

Here is the mechanism at the centre of it, and it's a double hit from one signal. Drag insulin up and watch both outputs move — androgen production climbing, SHBG falling — and the result they combine into.

The double hit
Drag insulin up. One signal, two effects: more androgen made, and less SHBG to bind it. They multiply.
Ovarian androgen production
↑
Normal
SHBG (the carrier that binds it)
↓
Ample
Result — free, active androgen
In balance
Insulin levelNormal
Illustrative of the direction of change — not exact quantities.

Insulin acts on the ovary's theca cells to increase androgen production — working alongside the pituitary hormone LH.[2] At the same time, it suppresses the liver's output of sex hormone-binding globulin (SHBG), the carrier that normally keeps most sex hormone bound and inactive.[3] So high insulin raises the supply and frees a larger fraction of it — the double hit.

The vicious cycle

The fire feeds the androgens, and the androgens feed the fire.

Insulin resistance is present in a large share of women with PCOS — strikingly, often including lean women, not only those carrying extra weight.[4] The body compensates for the resistance with more insulin, and that high insulin drives more ovarian androgen and lowers SHBG further — which in turn worsens the metabolic picture. A self-reinforcing loop.

An elegant symmetry. This is the mirror image of menopause: PCOS is the reproductive-age version, where high insulin drives ovarian androgens; menopause is a different entry point — oestrogen withdrawal — that lands on the same insulin-resistant, low-SHBG, central-adiposity picture. Same destination, different door.
A puzzle worth naming

The paradox, again — why the ovary still listens.

If these women are insulin-resistant, how does insulin still drive the ovary so effectively? The answer is the same selective, tissue-specific pattern that explained fatty liver. The classic insulin resistance of PCOS is in muscle and fat — the glucose-handling pathway — while the ovarian pathway through which insulin drives androgen production remains responsive.[4]

So the ovary keeps hearing the half of the message that says "make androgens" even as the muscle goes deaf to "take up glucose." It is the same shape as the liver in fatty liver disease — selective resistance, one pathway ignored and another obeyed — which is why PCOS, fatty liver and the rest of the fire are best understood as one family, not a scatter of separate diseases.

Masking the symptom, missing the root

Why it is so often mismanaged.

The commonest first-line treatment — the combined oral contraceptive pill — regularises bleeding and reduces androgen symptoms, and for many women that relief is genuinely valuable. But it works by overriding the reproductive signals, not by addressing the insulin driving them: it manages the symptom while the metabolic root rolls on underneath, much as the drugs in the other chapters manage a marker while the fire burns. Women with PCOS often report long diagnostic delays and little discussion of the metabolic dimension at all.

The tell, as in every chapter. A condition whose root, for many, is high insulin is routinely managed without anyone measuring insulin — while the treatment offered addresses the ovaries rather than the signal reaching them. Naming the metabolic root doesn't make the reproductive care wrong; it makes it half the picture.
Question Three
What addresses the root?

The 2023 international guideline places lifestyle — with a clear emphasis on improving insulin sensitivity — as a foundation of PCOS management, alongside medical treatments chosen for a woman's particular goals.[1] Read through this series' lens, the through-line is the same: lower the insulin load, and you reach the ovarian androgen drive and the SHBG suppression together.

  • Lower the insulin load — reducing refined carbohydrate eases the signal driving ovarian androgens and lifts SHBG; the most on-mechanism lever, and one that reaches the fertility and the metabolic risk at once.
  • Insulin-sensitising treatment where appropriate — metformin, and in some women inositol, are used to improve insulin sensitivity; these are medical decisions, guided by a doctor.
  • Muscle and movement — exercise improves insulin sensitivity directly, independent of weight.
The honest boundaries. PCOS is heterogeneous — insulin resistance is central for a large share but not every woman, so this is not a claim that a single dietary change "cures" all PCOS. Fertility, medication and symptom management are individual clinical decisions. And if any treatment is changed, that is a conversation with a doctor. What the mechanism does offer is a reason the metabolic root deserves a seat at the table it too often doesn't get.
Where this leaves you

Both halves deserve a place in the care.

PCOS is named for the ovaries, and the ovaries are where its signs appear — but for a great many women the driver is upstream: high insulin, raising ovarian androgens and freeing them by lowering SHBG, in a self-reinforcing loop. It is the same selective, tissue-specific insulin resistance that fills the liver with fat, reached in a different organ. And as of 2026, the field has said so out loud: the condition's own name now leads with "metabolic."

Not a reproductive condition that happens to carry metabolic risk — for many, the metabolic fire surfacing in the reproductive system.

Ask your body what is driving the androgens — and whether anyone is measuring it.

One face of the one fire. Back to the whole: The Invisible Fire.

A final word

Named for the ovaries, driven from the fire.

That reframing changes the questions worth asking — not only "how do we regularise the cycle?" but "what is driving the androgens, and is anyone measuring it?" The reproductive care matters. So does the root. A woman deserves both.

Named for the ovaries, driven from the fire — and both halves deserve a place in the care.

Verified references

[1] Teede HJ et al. (2023). Recommendations from the 2023 international evidence-based guideline for the assessment and management of PCOS. J Clin Endocrinol Metab 108(10):2447-2469. PMID 37580314. Read →

[2] Nestler JE (1997). Insulin regulation of human ovarian androgens. Hum Reprod 12(Suppl 1):53-62. PMID 9403321. Read →

[3] Wallace IR, McKinley MC, Bell PM, Hunter SJ (2013). Sex hormone binding globulin and insulin resistance. Clin Endocrinol (Oxf) 78(3):321-329. PMID 23121642. Read →

[4] Diamanti-Kandarakis E, Dunaif A (2012). Insulin resistance and the polycystic ovary syndrome revisited: an update on mechanisms and implications. Endocr Rev 33(6):981-1030. PMID 23065822. (The central, tissue-selective role of insulin resistance, including in lean women.) Read →

[5] Teede HJ, Piltonen T, Dokras A, et al. (2026). Polyendocrine metabolic ovarian syndrome, the new name for polycystic ovary syndrome: a multistep global consensus process. The Lancet. Published online 12 May 2026. PMID 42119588. DOI 10.1016/S0140-6736(26)00717-8. (The official 2026 rename to PMOS and the consensus reasoning — the shift toward the metabolic and endocrine root.) Read →