MOSS: PCOS has a new name, we explain everything

If you have heard of PCOS, you may have recently come across a mysterious new acronym: MOPOS. Rest assured, this is not a new disease being added to the list. It is simply PCOS changing its name, and this change is significant: it reflects a better understanding of this syndrome that affects millions of women. We explain everything, without the unnecessary jargon.

What exactly is MOPOS?

The MOPOS stands for Metabolic Ovarian Polyendocrine Syndrome. It is the new official name for what was previously known as PCOS, or Polycystic Ovary Syndrome.

At first glance, it might seem like a simple administrative update. In reality, every word in this new acronym was chosen to correct an inaccuracy in the old term:

• Metabolic : the syndrome is closely linked to insulin resistance and sugar metabolism, a central mechanism found in the majority of affected women;
• Ovarian : the ovaries remain in the name because they are often the first visible sign (irregular cycles, ultrasound), but they are no longer presented as the sole cause;
• Polyendocrine : the syndrome involves several hormonal axes at once, not just the ovaries. The thyroid, the microbiome, and overall metabolic balance are all part of the picture.

In short, MOSS says something that PCOS did not clearly state: this syndrome is complex, it affects several body systems simultaneously, and it cannot be reduced to an ovarian problem.

Why change the name of such a well-known syndrome?

One might think that changing such an established name, used for decades, risks causing confusion. And that is a perfectly legitimate question. But the problem with the old term was very real, and it had concrete consequences on how women understood (or failed to understand) their own situation.

The problem with the word "polycystic"

The term PCOS implied that the presence of cysts on the ovaries was the central characteristic, or even the cause, of the syndrome. This creates two problems.

First, medically speaking, what is observed on an ultrasound is not actually cysts. They are immature follicles, which fail to develop fully to release an egg. The word "polycystic" was therefore, technically, inaccurate.

Next, and this is perhaps the most important point for you in your daily life: many women grew up thinking they could not have PCOS if they did not have "polycystic" ovaries visible on an ultrasound. Yet it is entirely possible to have PCOS without this characteristic ovarian appearance, just as it is possible to have polycystic-appearing ovaries without being ill. The name therefore created confusion that likely delayed diagnosis for many women.

The term PCOS wrongly suggested that the ovaries were the cause of everything. MOSS places the syndrome back into its real context—metabolic and hormonal—with the ovaries acting as an indicator rather than the sole culprit.

A syndrome, not a single disease

Another key point of this name change: it serves as a reminder that we are talking about a syndrome, meaning a collection of signs and mechanisms that can vary considerably from one woman to another. There is no single MOSS, but rather several subtypes, with very different presentations depending on the woman: some will primarily have signs of hyperandrogenism (acne, excess hair growth), others will be mainly affected by insulin resistance, and others will experience a combination of several of these dimensions.

This diversity also explains why research on the subject continues to evolve rapidly, and why classifications will likely become even more refined in the coming years.

MOSS and PCOS: a transition period

If you still see the term PCOS used everywhere—on medical websites, by your gynecologist, or even here on Reflet—it is not a mistake. A two-year coexistence period has been scheduled between the two terms: PCOS and PMOS can be used interchangeably during this transition phase. After these two years, the term PCOS is set to become obsolete in favor of PMOS.

This transition period is useful because such an established name change takes time to become habitual, both for patients and healthcare professionals. Some doctors will likely continue to refer to PCOS out of habit for several more years, which is completely normal.

What PMOS actually changes for you

If you have already been diagnosed with PCOS, the good news is that this name change does not in any way call into question what you already know about your situation. The mechanisms are the same, the management is the same, and the natural solutions that worked yesterday still work today.

What PMOS primarily brings is a shift in perspective. Rather than focusing solely on your ovaries, the approach encourages you to look at your overall metabolic and hormonal balance: your insulin sensitivity, your thyroid, your microbiota, and your inflammation levels. This is exactly the logic of a holistic and natural approach to the syndrome, rather than trying to "treat" only the ovaries.

If you have never been diagnosed but have doubts, this name change can also be an opportunity to get informed again, especially if you were told in the past that you "did not have PCOS" simply because your ovaries did not have that typical polycystic appearance on an ultrasound.

The diagnosis has not yet changed

It is important to clarify one thing: even though the name is evolving, the official diagnostic criteria have not yet been updated at the same pace. The diagnosis is still based on the Rotterdam criteria, which require at least two of the following three elements: cycle irregularities, signs of excess androgens, and polycystic-appearing ovaries on an ultrasound.

It is likely that these criteria will also evolve in the coming years to better align with the new terminology, particularly regarding the issue of imaging-based diagnosis. But for now, this remains the framework used by doctors.

Key takeaways

• The PMOS (Polycystic Metabolic Ovarian Syndrome) is the new official name for PCOS ;
• This change corrects an inaccuracy in the old term, which centered everything on the ovaries when the syndrome is much broader (metabolic, hormonal, polyendocrine);
• A two-year coexistence period allows both terms to be used interchangeably;
• Every woman has her own unique PMOS, with very different presentations depending on the subtypes;
• The official diagnostic criteria have not yet evolved at the same pace as the name; they are still based on the Rotterdam criteria.
• If you have already been diagnosed with PCOS, nothing changes in terms of your care.

At Reflet, our series Sans Règles SOPK, created with Carole Minker, a doctor of pharmacy and expert in women's natural health, remains entirely relevant despite this name change. In it, we explain in detail the mechanisms that now make up MOSS: insulin resistance, natural therapies, nutrition, stress management, and much more.