A landmark article published in The Lancet on 12 May 2026 (Teede et al.) proposes renaming polycystic ovary syndrome (PCOS) to polyendocrine metabolic ovarian syndrome (PMOS), following a rigorous, multistep global consensus process. The new name reflects the condition’s polyendocrine, metabolic, and ovarian pathophysiology, removes the misleading reference to ovarian cysts, and has been widely welcomed by both the clinical community and patient advocates. Notably, the authors explicitly name SNOMED CT as a target system for adoption as part of a planned three-year global implementation strategy.
This raises a direct question for our community: should SNOMED CT adopt PMOS, and if so, how?
The question is not purely one of naming. The current SNOMED CT concept for PCOS is modelled as an ovarian disorder. PMOS, by definition, is a polyendocrine metabolic condition that extends well beyond the ovary. This means that simply renaming the existing concept would constitute a change in meaning — which under SNOMED editorial principles requires inactivation and replacement with a correctly modelled new concept, not merely a description update. The downstream impacts on value sets, maps, and coded patient data would need careful management.
Possible approaches include:
No change yet — monitor clinical and ICD uptake before acting
Add PMOS as a synonym now — with preferred term status and remodelling deferred to a defined milestone such as ICD adoption or the 2028 International Guidelines update
Inactivate the existing concept and create a new correctly modelled PMOS concept — the editorially rigorous path, with PCOS retained as a historical synonym and appropriate replacement associations provided for implementers
We would welcome community views on the following:
Does the robustness of this consensus process justify early action in SNOMED CT?
Which approach best balances editorial integrity, implementer impact, and patient benefit?
What milestone should trigger full adoption if a deferred approach is preferred?
Should PCOS be retained indefinitely as an acceptable synonym or deprecated over the transition period?
I shared the US NRC response in the MF Forum post, but will share it here for the CMAG as well:
We recommend Option #2, which adds PMOS as a synonym now. Once the new PMOS concept is created, PCOS should be inactivated, as you have already noted, because the condition’s underlying definition has changed. This should also include inactivating the PCOS children:
We have received change requests from clinicians following the announcement that Polycystic Ovary Syndrome (PCOS) has been renamed Polyendocrine Metabolic Ovarian Syndrome (PMOS).
We support Option 2: adding PMOS as a synonym during the transition period, allowing clinicians to use the updated terminology while clinical guidelines and systems are updated.
I agree with Nick that, following establishment of the new PMOS concept, PCOS and its child concepts should be inactivated to reflect the revised definition.
I agree with the approach of 2, followed by 3. Even if we jumped straight to 3, we’d probably assign PCOS as the Preferred Term until the clinicians asked for otherwise.
The current modelling is probably already questionable without this new description. Like most syndromes it’s a constellation of symptoms, and ovarian cysts are only one of the possibilities. (not the defining property despite the name):
The names we give things aren’t always accurate. “Tennis elbow” is the obvious one; many (most?) people with it have never picked up a racquet.
The subtypes of 86157004 |Occupational lung disease| name the occupation rather than the agent, e.g. 19274004 |Grain-handlers’ disease|, 61233003 |Silo-fillers’ disease|, 25897000 |Malt-workers’ lung|. These all describe the occupation, not the actual causative agents.
The precedent for handling name changes is by inactivating and replacing, not relabelling in place:
602001 |Ross river fever| became 789400009 |Disease caused by Ross River virus|, re-based on 246075003 |Causative agent| = 32458000 |Ross River virus|. These are almost certainly describing the same thing with “Fever” a legacy word for “illness”. “Ross River fever” was kept as a synonym and is still our PT in AU;
23782005 |Wegener’s granulomatosis| to 195353004 |Granulomatosis with polyangiitis| went the same way (though the eponym doesn’t exist as a synonym)
A new, correctly modelled PMOS concept, with PCOS retained as a synonym and PT for now, would be defensible. I’d only hesitate about changing now, until there’s reliable clinical consensus.
The Journal of the Norwegian Medical Association, our biggest national medical journal, has published an article concerning the name change this spring. Terms in the patient information on the official website for health information and digital health services in Norway were updated to PMOS in May. The general media has also focused several series of articles on the topic, and the national patient organization/interest group for this diagnosis have already changed their name from PCOS Norway to PMOS Norway.
A short questionnaire was sent to clinical experts in a regional hospital in Norway regarding the proposed changes and possible options. One specialist in gynecology responded that option number 2 would be appropriate for clinical use cases, as this would give researchers, literature and the clinicians more time to get used to the new term.
The Norwegian NRC are of the opinion that adding PCOS as a synonym to a new concept for PMOS, or even adding PMOS as a synonym to the existing concept for PCOS, is in conflict with current guidelines for the terminology. As such, we would prefer option number 3.
The presence of ovarian cysts is not a necessarily a factor in the diagnosis of a patient with PMOS - they might “only” have the other two qualifying symptoms to receive the diagnosis. Furthermore, the description stating cysts is also somewhat imprecise, as the masses visible in imaging are most prevalently arrested follicular development and not the classical understanding of a pathological ovarian cyst in this patient group. These key differences lead us to think that PMOS and PCOS cannot at any point in time be reckoned as true synonyms of one another.
If the goal of adding a synonym to one concept or another in this matter is to improve searchability, perhaps a middle ground could be to add the outdated term PCOS in a text definition for the new concept for PMOS, as has been done with 702772003 |Idiopathic environmental intolerance (disorder)|, 788950000 |Heart failure with mildly reduced ejection fraction (disorder)| and 722456001 |Intellectual disability, developmental delay, contracture syndrome (disorder)|, among others.