Endometriosis vs. PCOS: What’s the Difference?

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Dr Kelly Loi
Dr Kelly Loi

Senior Consultant Obstetrician & Gynaecologist

Medical Director & Clinical Governance Officer (CGO) of Monash IVF Singapore

Medical Director of Health & Fertility Centre for Women

Many women experience symptoms such as irregular periods, painful menstruation or difficulty conceiving at some point in their lives. Two conditions that are often mentioned in these conversations are endometriosis and polycystic ovary syndrome (PCOS). While they may share some overlapping symptoms, they are actually very different conditions with distinct causes, effects and treatment approaches. Understanding the differences between endometriosis and PCOS can help women recognise potential signs early and seek appropriate medical advice.

What Are Endometriosis and Polycystic Ovarian Syndrome?

Although they may share certain symptoms, such as menstrual irregularities or fertility concerns, the underlying causes and how they affect the body are quite different.

Endometriosis

Endometriosis occurs when tissue similar to the lining of the uterus grows outside the uterus, such as on the ovaries, fallopian tubes, or other areas within the pelvis. This tissue responds to hormonal changes during the menstrual cycle, which may lead to inflammation, irritation and scar tissue over time.

Women with endometriosis may experience symptoms such as painful periods, chronic pelvic pain, heavy menstrual bleeding or discomfort during intercourse. However, symptoms can vary widely and some women may have minimal symptoms while others experience more significant discomfort.

Polycystic Ovary Syndrome (PCOS)

PCOS is a hormonal condition that affects how the ovaries function. Women with PCOS may experience hormonal imbalances that can disrupt regular ovulation.

Common signs of PCOS include irregular or missed periods, acne, excess facial or body hair and difficulty conceiving. Some women may also develop multiple small follicles in the ovaries, which can be seen during an ultrasound examination.

What Symptoms Do Endometriosis and PCOS Have in Common?

Although endometriosis and PCOS are different conditions, they can share some similar symptoms. Because of these overlaps, it may sometimes be difficult to distinguish between the two without a proper medical evaluation.

  • Changes in menstrual patterns: Irregular cycles, heavy menstrual bleeding or other disruptions to the usual period pattern may occur in both conditions.
  • Difficulty conceiving: Both can affect fertility, though in different ways. Endometriosis may impact the pelvic organs, while PCOS can interfere with regular ovulation.
  • Pelvic discomfort or abdominal bloating: Some women experience pain or a sensation of fullness in the abdomen, although the type and severity can differ between conditions.
  • Overlap with other symptoms: While not identical, there can be some overlap in general discomfort. Endometriosis is more often linked to severe menstrual pain, whereas PCOS is more commonly associated with hormonal symptoms such as acne or excess hair growth.

What Are the Key Differences Between Endometriosis and PCOS?

While endometriosis and PCOS can share some symptoms, they affect the body in different ways. Understanding these differences can help women recognise which condition may be more consistent with their symptoms and why proper medical evaluation is important.

Underlying Cause

Endometriosis occurs when tissue similar to the lining of the uterus grows outside the uterus, often leading to inflammation and pelvic pain. In contrast, PCOS is a hormonal condition that affects how the ovaries function and can disrupt ovulation.

Certain Symptoms

Endometriosis is more commonly associated with severe menstrual cramps, chronic pelvic pain and pain during intercourse. PCOS, on the other hand, is often linked to hormonal symptoms such as acne, excess facial or body hair and difficulty with ovulation.

Menstrual Patterns

Women with endometriosis may still have regular menstrual cycles, although their periods can be particularly painful or heavy. Women with PCOS are more likely to experience irregular or missed periods due to inconsistent ovulation.

Diagnosis

Diagnosing endometriosis may involve imaging tests and, in some cases, minimally invasive surgery such as laparoscopy to confirm the presence of endometrial-like tissue outside the uterus. PCOS is typically diagnosed based on a combination of symptoms, blood tests to assess hormone levels and ultrasound findings.

While the two conditions are distinct, it is possible for some women to have both endometriosis and PCOS. Consulting a gynaecologist can help ensure an accurate diagnosis and an appropriate management plan.

When Should You See a Gynaecologist?

Because endometriosis and PCOS can share similar symptoms, it may not always be easy to identify the underlying cause without a proper medical evaluation. If certain symptoms persist or begin to affect your daily life, it may be helpful to consult a gynaecologist. You may wish to seek medical advice if you experience:

  • Severe or worsening menstrual pain that interferes with daily activities.
  • Irregular or missed periods.
  • Heavy menstrual bleeding or periods that last longer than usual.
  • Persistent pelvic pain or discomfort.
  • Acne or excess facial or body hair, linked to hormonal changes.
  • Difficulty conceiving after trying for some time.

Specialist Care for Both Endometriosis and PCOS

Although endometriosis and PCOS can present with similar symptoms, understanding how they differ is key to receiving the right care. Paying attention to changes in your menstrual cycle, pelvic health or fertility can help you identify when it may be time to seek medical advice.
Health & Fertility Centre for Women provides comprehensive, patient-centred care for women’s gynaecological and fertility health. Patients are carefully assessed in the trusted hands of Dr Kelly Loi, an Oxford-trained doctor and Fellow of the Royal College of Obstetricians and Gynaecologists (UK) as well as the Academy of Medicine (Singapore). If you are experiencing symptoms or have questions about your gynaecological health, arranging a consultation can help you receive a detailed evaluation and discuss suitable treatment options.

FAQs About Endometriosis and PCOS

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