Two women can both have PMOS and have almost nothing in common symptom-wise. One has acne, thick facial hair, and irregular periods. The other has perfectly regular-looking skin, regular-ish cycles, but her ovarian ultrasound looks unusual and her blood sugar is creeping up. Both have PMOS. Both need very different care.
This is why “just treat the PCOS” has failed so many women. Because PMOS isn’t one thing. It’s a spectrum with four distinct presentations - called phenotypes - and which one you have changes everything about which tests matter, what treatments work, and what long-term risks to watch for.
First: the three things doctors check
To diagnose PMOS, doctors use a framework called the Rotterdam criteria - established in 2003 and still the global standard today. The rule is simple: you need to have at least 2 of these 3 things (after ruling out other causes).
Source: 2023 International Evidence-Based PCOS Guidelines, ASRM
Good news: if you have both irregular periods and elevated androgens (criteria 1 + 2), your doctor can diagnose you without an ultrasound at all. That covers about 60% of women with PMOS.
The 4 phenotypes, in plain English
Depending on which two (or all three) criteria you meet, you fall into one of four phenotypes. Think of them less as rigid categories and more as different flavours of the same underlying condition. The letters A through D come from a 2012 NIH workshop - but what matters isn’t the letter, it’s what it means for your body.
Sources: NIH PMC - Phenotype and Metabolic Disorders · RRM Academy · ScienceDirect, 2024
Why does your phenotype matter so much?
“Flying blind on phenotype means treating every PMOS presentation the same way - and that’s how patients cycle through protocols for years without resolution.”
Here’s a concrete example. If you have Phenotype A or B, your insulin resistance is likely driving your symptoms. Treating your acne without addressing the insulin piece is like mopping the floor while the tap is still running. The metabolic workup - fasting insulin, glucose tolerance test, lipids - isn’t optional for you. It’s where treatment starts.
Phenotype C, on the other hand, might respond well to targeted hormonal support without the full metabolic intervention. And Phenotype D often does well with ovulation induction approaches, without necessarily needing insulin-sensitising medications at all.
OGTT, fasting insulin, lipids are essential first steps
Same metabolic workup as A, even without visible PCOM
Lipids and glucose worth checking; less urgent than A/B
Basic metabolic screen; ongoing monitoring important
Source: RRM Academy Phenotype Glossary · 2023 International Guidelines
One important thing to know
Phenotype is not a life sentence. It can shift over time, with age, weight changes, or treatment. A woman who presents as Phenotype A in her twenties may look more like Phenotype C in her late thirties as metabolic and hormonal patterns evolve. This is why ongoing monitoring matters - which we’ll cover in Part 4.
It’s also worth knowing that many women are never phenotyped at all. A diagnosis of “PCOS” often comes without any follow-up on which kind - which is part of why so many women feel like the treatment they were given never quite fit. Asking your doctor “which phenotype do I have?” is a legitimate and important question.
The right vocabulary helps. Walking into a consultation knowing whether you have Criterion 1, 2, or 3 - and which combination - helps you advocate for the right tests and the right treatment. In Part 3, we lay out exactly which blood tests matter for each type.