When a doctor confirms PCOS, they do not rely on a single test or a single symptom. They use a framework called the Rotterdam criteria, a system adopted worldwide since 2003 and still the foundation of the 2023 international PCOS guideline. The logic is simple but important to grasp: you need to meet 2 of 3 features, not all three. Many Malaysian women worry because their ultrasound came back “normal”, when in fact they may still qualify for a diagnosis through the other two features.
What the Rotterdam criteria are and where they came from
The Rotterdam criteria were created at an expert conference in Rotterdam, the Netherlands, in 2003. Before that, a stricter definition (NIH 1990) required both irregular periods and signs of high androgens. Rotterdam widened the definition so that more women who genuinely have PCOS would not be missed.
The principle: PCOS is confirmed when two of the three features below are present, after other causes are excluded:
- Irregular periods (oligo-ovulation or anovulation), meaning infrequent, long, or absent cycles where ovulation does not occur.
- Signs of high androgens (hyperandrogenism), either clinically (hirsutism, stubborn acne, thinning hair) or biochemically through a testosterone blood test.
- Polycystic ovaries on ultrasound, or a high AMH level.
This is why someone can be diagnosed with PCOS even when their ovaries look normal, as long as the other two features are present. It is one of the most common misunderstandings we see in the community.
The three features explained one by one
Feature 1: Irregular periods. Cycles longer than 35 days, fewer than eight a year, or simply absent for months point to disrupted ovulation. For some women, cycles look “regular” yet ovulation still fails to happen, so doctors sometimes check a day-21 progesterone to confirm.
Feature 2: High androgens. The clinical version means hair growing in a male pattern (chin, upper lip, chest, abdomen), persistent acne, or scalp hair thinning at the crown. The biochemical version is seen through raised total and free testosterone. You only need to meet one, either the physical signs or the blood-test numbers, not both.
Feature 3: Polycystic ovaries or high AMH. On ultrasound, “polycystic” means many small follicles. The 2023 guideline updated the threshold to 20 or more follicles (sized 2 to 9 mm) in one ovary, or an ovarian volume of 10 mL or more. Another major change is that the AMH (Anti-Müllerian Hormone) level can now be used in place of ultrasound, because AMH closely tracks follicle count.
But one point matters: the evidence for AMH is graded moderate, not definitive. The 2023 guideline stresses that there is no single universal AMH cut-off, because results vary by laboratory assay, age, and body weight. AMH also cannot be used on its own to diagnose PCOS; it only substitutes for ultrasound in the “polycystic ovaries” item, and must still be paired with one of the other features. So if your lab reports a high AMH, that is one clue, not an automatic diagnosis.
The four Rotterdam phenotypes and why they matter
Because you only need to meet two of the three features, PCOS actually exists in four different combinations called phenotypes. Understanding them helps explain why two women with PCOS can have very different experiences.
- Phenotype A (classic): all three features present, namely irregular periods, high androgens, and polycystic ovaries. This is the most complete form and is usually linked to the most pronounced insulin resistance.
- Phenotype B: irregular periods and high androgens, without polycystic ovaries. Its metabolic risk is also high.
- Phenotype C (ovulatory): high androgens and polycystic ovaries, but periods still happen regularly. Its metabolic impact tends to be milder than A and B.
- Phenotype D (non-androgenic): irregular periods and polycystic ovaries, without signs of high androgens. This is the phenotype least associated with insulin resistance.
Why does this matter in Malaysia? Because the three phenotypes with high androgens (A, B, and C) generally carry a heavier metabolic burden, meaning a greater tendency toward insulin resistance and future type 2 diabetes risk. Knowing your phenotype helps your doctor tailor monitoring more precisely, for example how often blood-sugar testing should be done. Even so, a phenotype is not a permanent label, and it does not replace a full assessment by your doctor; it is simply one way to understand the pattern of your condition.
How it differs in Malaysia
In Malaysia, one important point touches the third feature. For women who are unmarried or have had no prior intercourse, a transabdominal (through the belly) ultrasound is the first choice, not transvaginal. This scan is less precise for counting small follicles, but that is not a problem, because PCOS can still be diagnosed without a transvaginal scan if the other two features already qualify. Do not feel forced into a transvaginal scan if you are uncomfortable; discuss the transabdominal ultrasound or an AMH test with your doctor instead.
On access, you can start the process at a KKM Klinik Kesihatan for around RM1 for citizens, including basic investigations. The clinic doctor will refer you to a hospital O&G or endocrine clinic if needed, with specialist follow-up costs still low compared to private care. Private clinics offer shorter waiting times but their fees vary, so confirm directly with the clinic concerned.
Why exclusion matters as much as the features
The part most often overlooked is the phrase “after other causes are excluded”. PCOS is a diagnosis of exclusion, meaning a doctor must make sure your symptoms are not caused by another condition that mimics it. Common exclusion blood tests include:
- TSH to rule out thyroid problems.
- Prolactin to rule out hyperprolactinaemia.
- 17-hydroxyprogesterone (17-OHP) to rule out non-classic congenital adrenal hyperplasia (NCAH).
In more severe or unusual cases, such as very high androgens or features of Cushing’s, the doctor may add further tests. Without this step, someone can be wrongly labelled with PCOS when the real cause is different and needs other treatment. For the full panel, see the complete PCOS blood test guide.
Special situations: adolescents and “two clear features” cases
For adolescents (within eight years of their first period), the guideline is more cautious. Ultrasound and AMH are not recommended for this age group, because ovaries with many follicles are normal in young women. Instead, an adolescent diagnosis requires both irregular periods and signs of high androgens.
On the other hand, if an adult woman clearly has irregular periods and signs of high androgens, the 2023 guideline states that ultrasound or AMH are no longer required to confirm the diagnosis. Those two features are enough.
What to ask your doctor during the diagnosis process
A PCOS diagnosis should be a conversation, not a one-way verdict. Bringing a few precise questions helps you understand where you stand. Useful ones to ask include:
- “Which Rotterdam features have I already met, and which have I not?”
- “Have the exclusion tests such as TSH, prolactin, and 17-OHP been done, or do they still need to be?”
- “If my ovaries cannot be assessed clearly on a transabdominal ultrasound, is an AMH test an option for me?”
- “Based on my features, which phenotype describes my situation, and what does it mean for my diabetes and heart risk?”
- “How often should I check my blood sugar, blood pressure, and lipid profile from now on?”
Note down the answers, and ask for a copy of your test results to keep. This information is useful when you are referred to another clinic or change doctors.
After you meet the criteria
Meeting the Rotterdam criteria is only a starting point, not the finish line. A diagnosis opens the door to a treatment plan and, just as importantly, awareness of long-term risks. Many Malaysian women do not realise that PCOS raises the future risk of type 2 diabetes and heart disease, so ongoing metabolic monitoring matters even when symptoms appear controlled.
You may also have heard the newer term PMOS (Polyendocrine Metabolic Ovarian Syndrome), formerly PCOS. Although the name is in a global transition, the diagnostic criteria have not changed: the same Rotterdam framework is still used, and clinics and official records in Malaysia still use the term PCOS.
If you have just been diagnosed and wonder what comes next, the newly diagnosed PCOS guide lays out your first-week actions in order. To understand the condition as a whole, start with what PCOS is. And before buying any supplements, remember that no supplement replaces a doctor’s diagnosis or treatment; talk to your gynaecologist or endocrinologist first before starting any product, especially if you are pregnant or breastfeeding.