Many women in Malaysia walk into the clinic with the same question: “Is this PCOS or endometriosis?” Both involve hormones, fertility, and the menstrual cycle, so it is easy to mix them up. Yet in reality these two conditions are almost opposites in terms of their cause. Understanding the difference helps you ask your doctor the right questions and avoid wasting time on the wrong treatment.
This article compares the two: what they share, where they diverge, and which sign is most useful for telling them apart. If you have just been diagnosed, start with the newly diagnosed guide as well.
Two problems, two different causes
The underlying cause of these two conditions is not the same at all, and this is the key to understanding them.
PCOS (polycystic ovary syndrome) is a hormonal and metabolic problem. The body produces excess androgens (“male” hormones such as testosterone), ovulation becomes irregular, and many patients also have insulin resistance. The ovaries may contain many small, immature follicles, but these are not painful “cysts”. PCOS is more about a hormone and energy imbalance than about swollen tissue.
Endometriosis, on the other hand, is a tissue and inflammation problem. Tissue resembling the lining inside the uterus (the endometrium) grows in the wrong place, outside the uterus, usually on the ovaries, fallopian tubes, or bowel. Each month this tissue responds to oestrogen, bleeds, and triggers inflammation and scar tissue. This is what causes the pain.
An easy way to remember it: PCOS leans toward androgen dominance and metabolic problems, while endometriosis is driven by oestrogen and inflammation. Two very different mechanisms, even though the surface symptoms sometimes overlap.
In terms of how many are affected, neither condition is rare. PCOS affects roughly one in five to one in eight women of reproductive age, while international health bodies estimate that endometriosis affects about one in ten women of reproductive age worldwide. That means many Malaysian women live with one of these conditions without a clear diagnosis, often because the symptoms are dismissed as “just normal periods” or “a woman’s fate”. That assumption is exactly what needs to be challenged.
The most helpful clue: the pain pattern
If you can focus on only one clue, focus on pain.
Endometriosis is known for very painful periods (dysmenorrhoea) that get worse from year to year. The pain often starts before the period, can be continuous, and sometimes becomes debilitating enough to interfere with work or school. Other signs include pain during intercourse (dyspareunia), pain when passing stool or urinating during a period, and sometimes spotting between periods. This recurring, cyclical pain is its hallmark.
PCOS, by contrast, is usually not painful. Its main problem is infrequent, late, or absent periods because ovulation does not happen regularly. Women with PCOS more often complain about weight that is hard to control, stubborn acne, excess hair on the face and body (hirsutism), or thinning scalp hair. If your periods are irregular but not especially painful, and you notice signs of high androgens, that picture points more toward PCOS. For details, read what PCOS is.
Even so, pain is not a perfect test. Some women with endometriosis have mild pain, and some women with PCOS get ordinary period cramps. The pain pattern is a strong clue, not a final confirmation.
A quick comparison
This quick table can help you see the main differences at a glance. It is a general guide, not a self-diagnosis tool.
| Aspect | PCOS | Endometriosis |
|---|---|---|
| Main cause | Hormonal and metabolic (high androgens, insulin resistance) | Tissue and inflammation (oestrogen-driven) |
| Periods | Infrequent, late, or absent | Usually present, but very painful |
| Pain | Usually mild or none | Severe, worsening, cyclical |
| Other typical signs | Acne, hirsutism, weight gain | Pain during intercourse, pain on passing stool |
| Source of fertility trouble | Irregular ovulation | Scar tissue, blocked tubes, egg quality |
| Main tests | Hormone blood tests and ultrasound | Examination, imaging, sometimes laparoscopy |
| Long-term risks | Type 2 diabetes, heart disease, endometrial cancer | Chronic pain, infertility, adhesions |
How each one is diagnosed
The way doctors confirm these two conditions also differs, and this is important to understand before heading to the clinic.
With PCOS, there is no single test that gives the answer. Doctors use international criteria (the Rotterdam criteria) that require two of three features: irregular ovulation, signs of high androgens (by examination or blood test), and many follicles or an enlarged ovarian volume on ultrasound. Other conditions such as thyroid problems must be ruled out first. In Malaysia, for women who are unmarried or have never had intercourse, an abdominal (transabdominal) scan is used as the first choice rather than a transvaginal scan. PCOS can still be diagnosed without a transvaginal scan.
With endometriosis, the main confirmation method used to be laparoscopic surgery, where a small camera is inserted through a tiny opening in the abdomen to view the tissue directly. Now, international guidance (ESHRE 2022) has shifted toward clinical diagnosis: doctors can suspect and treat endometriosis based on a combination of symptoms, examination, and imaging (ultrasound or MRI), without immediately requiring surgery. Laparoscopy is now more of an option when imaging is unclear or medication has not worked.
One real challenge with endometriosis is that ordinary imaging can look normal even when the disease is present. Superficial endometriosis on the pelvic surface often does not show up on ultrasound, so a clean scan does not rule out the diagnosis. This is why symptom assessment and a specialist’s experience still matter greatly, and why endometriosis is notorious for years-long diagnostic delays in many countries.
The practical difference: PCOS can usually be assessed with blood tests and ultrasound at a KKM Klinik Kesihatan, while endometriosis often needs a referral to a gynaecologist, and its diagnostic pathway can take longer.
Do not forget adenomyosis and fibroids
PCOS and endometriosis are not the only conditions that can disrupt periods. Two others that are often confused with them are adenomyosis and fibroids, and it is worth knowing they exist so you are not surprised if your doctor mentions them.
Adenomyosis occurs when tissue like the uterine lining grows into the muscular wall of the uterus itself. As a result, the uterus swells, periods become very heavy and clotted, and cramps become severe. Adenomyosis is more likely to cause heavy bleeding than endometriosis, and it can be assessed with ultrasound or MRI.
Fibroids are non-cancerous lumps of muscle that grow on or inside the uterus. Depending on their size and location, fibroids can cause heavy periods, a feeling of fullness or pressure in the lower abdomen, and sometimes difficulty conceiving. Fibroids are also detected by imaging.
The main reason all four conditions are mentioned together: severe period pain and bleeding are not typical features of PCOS. So if that is your main complaint, your doctor will lean toward thinking about endometriosis, adenomyosis, or fibroids rather than blaming PCOS alone.
Effects on fertility, by two different routes
Both conditions can make pregnancy harder, but for different reasons, and this is often the biggest worry for Malaysian women.
In PCOS, the problem is ovulation. Eggs are not released regularly, so the chance of conceiving drops. Ovulation can often be stimulated, and managing weight and insulin resistance usually helps.
In endometriosis, the problem is more mechanical and inflammatory. Scar tissue can damage or block the fallopian tubes, disrupt ovarian function, and affect egg quality. Endometriosis is linked to a large share of otherwise unexplained infertility.
If you have both conditions at once, the fertility challenge can be greater. Studies have found that women with PCOS and endometriosis together have a higher risk of infertility than those with only one condition. This is not meant to frighten you, but to underline the importance of a thorough evaluation rather than an assumption.
If you are struggling to conceive, do not assume the cause yourself. A proper evaluation will determine whether the issue is with ovulation, the tubes, or a combination of both.
Treatment also heads in different directions
Because the causes differ, the treatments for the two conditions also head in different directions, and this is exactly why an accurate diagnosis matters so much.
With PCOS, the focus of treatment depends on your goals. If you are not planning a pregnancy, the doctor may focus on stabilising the menstrual cycle, controlling acne and excess hair, and addressing insulin resistance through lifestyle changes and sometimes medication such as metformin. If you are planning a pregnancy, the focus shifts to stimulating ovulation. Weight and nutrition management are often the foundation of treatment because they touch the metabolic root cause.
With endometriosis, treatment targets pain and inflammation. This may include pain relief, hormonal therapy to suppress the cycle and reduce tissue growth, and in some cases surgery to remove affected tissue. The approach for women who want to conceive is different from the approach for those who only want pain relief.
Note one important point: the combined contraceptive pill is often used in both conditions, but for different reasons. In endometriosis it helps suppress the cycle and relieve pain, while in PCOS it helps control androgens and stabilise periods. This is why treating without a clear diagnosis can mask the real problem that still lies beneath the surface.
Can someone have both at once?
Yes, and this is often forgotten. A woman can have PCOS and endometriosis at the same time. Studies in clinical populations have found that the rate of PCOS among women with endometriosis can reach around one in four, so having one condition does not rule out the other.
This is why it is important not to stop looking for answers after a single diagnosis. If you have already been confirmed to have PCOS but still get very painful, debilitating periods, tell your doctor, because that pain is not a typical feature of PCOS and may indicate something else happening at the same time.
Questions to ask your doctor
Bringing organised questions helps you get clearer answers in a short appointment. Some useful ones to ask:
- Based on my symptoms, which condition is more likely suspected, and why?
- Do I need hormone blood tests, imaging, or a referral to a specialist?
- If the scan looks normal, does that completely rule out endometriosis?
- Could I have more than one condition at the same time?
- Does this treatment target the cause or only relieve the symptoms?
- How could this condition affect my chances of conceiving in the future?
Also bring a record of your menstrual cycle, a pain scale, and a list of any medications or supplements you are taking. This information shortens the path toward a correct diagnosis.
When to see a doctor
See a doctor if you have periods that grow more painful over time, pain severe enough to interfere with work or school, pain during intercourse, very heavy or clotted periods, or periods that disappear for more than three months without explanation. Bring a record of your menstrual cycle and a list of your symptoms, because this information greatly helps the doctor tell the two conditions apart.
You can start at a KKM Klinik Kesihatan at low cost for citizens, and the doctor will refer you to a hospital gynaecology clinic if needed. A correct diagnosis is the first step, because the treatment for PCOS and endometriosis differs. Both conditions also carry long-term risks worth monitoring: PCOS is linked to a higher risk of type 2 diabetes and heart disease, while untreated endometriosis can lead to chronic pain and fertility problems. Identifying the right condition is not just about relief today, but about protecting your health for the years ahead.