There were never really any cysts

For decades, we have called it polycystic ovary syndrome — PCOS. In 2026, following a large international consensus process involving patients, clinicians and professional organisations worldwide, the condition was given a new name:

Polyendocrine Metabolic Ovarian Syndrome — PMOS.

This is not a new condition, and women previously diagnosed with PCOS do not need to be diagnosed again. The condition is the same. The name has changed because the old one did not describe it particularly well. The international guideline is transitioning to the new terminology, while its diagnostic and management recommendations remain unchanged.

And there was one particularly confusing word in the old name: POLYCYSTIC.

The small round structures we see on ultrasound in a “polycystic” ovary are not actually cysts. They are antral follicles — normal structures within the ovary, each containing an immature egg. I have lost count of how many times a patient has told me, “I have cysts on my ovaries,” only for me to discover that she has never had an ovarian cyst at all. She had been told that she had PCOS or “polycystic ovaries.”

This is more than a matter of terminology. Even for a gynaecologist, the word cyst means something quite different. When a patient tells me that she has been diagnosed with an ovarian cyst, I immediately want to know what kind: a simple functional cyst? A dermoid? An endometrioma? A serous or mucinous cystadenoma? Could it be a borderline ovarian tumour? These are actual ovarian cysts or cystic lesions, with very different clinical implications.

The follicles seen in PCOM are none of these things. Which brings us to another important distinction — and another abbreviation, sorry!

PCOM is not PMOS

(although whoever came up with those abbreviations certainly didn’t make things easy for us!)

PCOM — polycystic ovarian morphology — is an ultrasound description, not a diagnosis. It simply describes an ovary containing a relatively large number of small antral follicles. In an adult, with modern transvaginal ultrasound, PCOM is defined primarily by the presence of 20 or more 2–9 mm follicles in at least one ovary.

A high antral follicle count often reflects a good quantitative ovarian reserve. Many women with PCOM ovulate regularly, have normal androgen levels and have no metabolic abnormalities at all. Seeing many follicles on an ultrasound does not mean that a woman has PMOS.

And the reverse is also true: a woman can meet the diagnostic criteria for PMOS without having polycystic ovarian morphology. So an ultrasound image of an ovary cannot, by itself, diagnose the syndrome.

The ovary was never the whole story

The new name draws attention to something much more important. PMOS is not simply an ovarian condition — and it is certainly not just a fertility problem.

It is a complex endocrine, metabolic and reproductive syndrome. It can affect ovulation and menstrual cycles, androgen levels, skin and hair, insulin sensitivity and longer-term metabolic health. Its manifestations also vary considerably from one woman to another.

Fertility difficulties are only one possible face of PMOS. For some women, they may never be the most important one.

This is why Polyendocrine Metabolic Ovarian Syndrome is a much better name. It removes the misleading suggestion that the condition is defined by ovarian “cysts” and shifts attention towards what it actually represents: a multisystem disorder involving complex interactions between hormonal, metabolic and ovarian function.

Interestingly, while PCOS has now lost the misleading word “polycystic”, PCOM — polycystic ovarian morphology — has not. At least not yet. Perhaps “multifollicular ovarian morphology” (MFOM — so much easier!) would better describe what we actually see on ultrasound: multiple follicles, not multiple cysts. The term has already begun to appear in recent scientific literature, although PCOM remains the terminology used in the current international guideline. So perhaps PCOM should be next?