PCOS vs Endometriosis — Clinical Trial Comparison
PCOS
Hormonal imbalance with excess androgens
VS
Endometriosis
Oestrogen-driven tissue growth outside the uterus
Polycystic ovary syndrome (PCOS) and endometriosis are two of the most common gynaecological conditions in the UK, affecting millions of women. PCOS is a hormonal disorder characterised by excess androgens and irregular ovulation, while endometriosis involves tissue similar to the uterine lining growing outside the womb, causing inflammation and pain. Both significantly impact fertility and quality of life, and both have been historically under-researched — though that is changing rapidly.
Key Differences at a Glance
| Feature | PCOS | Endometriosis |
|---|---|---|
| Nature | Endocrine/metabolic disorder — excess androgens, insulin resistance, anovulation | Inflammatory condition — endometrial-like tissue outside the uterus |
| UK prevalence | ~8–13% of women of reproductive age | ~10% of women of reproductive age (~1.5 million) |
| Key symptoms | Irregular periods, acne, hirsutism, weight gain, difficulty conceiving | Severe period pain, chronic pelvic pain, pain during sex, fatigue, fertility issues |
| Diagnosis | Rotterdam criteria (2 of 3: irregular ovulation, hyperandrogenism, polycystic ovaries on ultrasound) | Laparoscopy (gold standard); clinical diagnosis + imaging increasingly accepted |
| Hormonal driver | Excess androgens (testosterone, androstenedione) | Oestrogen dependence (tissue responds to menstrual cycle hormones) |
| Fertility impact | Anovulation — can often be treated with ovulation induction | Structural damage, inflammation, egg quality — more complex fertility challenges |
Clinical Trial Availability
| Trial Aspect | PCOS | Endometriosis |
|---|---|---|
| UK trials actively recruiting | 15–25 studies | 20–30 studies |
| Most common trial phase | Phase 2–3 | Phase 2–3 |
| Top interventions tested | GLP-1 agonists, inositol supplements, lifestyle interventions, anti-androgens, ovulation induction | Anti-prolactin agents, novel hormonal therapies, GnRH antagonists, surgical techniques, pain management |
| Hormonal therapy trials | Combined oral contraceptives, anti-androgens (spironolactone) | GnRH agonists/antagonists, progestins, Dienogest, novel anti-oestrogens |
| Fertility trials | Major category (letrozole, clomiphene, IVF protocols) | Significant (surgical vs medical, IVF protocols, endometrioma management) |
| Diagnostic trials | Biomarker panels, genetic testing, ultrasound criteria | Blood biomarkers, MRI techniques, saliva tests, non-invasive alternatives to laparoscopy |
Exciting Emerging Treatments
PCOS Trials
- GLP-1 receptor agonists (semaglutide, tirzepatide) — targeting insulin resistance and weight management in PCOS
- Myo-inositol and D-chiro-inositol combinations — improving ovulation and metabolic parameters
- Novel anti-androgen topical agents — for hirsutism and acne without systemic side effects
- Lifestyle and digital health programmes — AI-guided diet and exercise for PCOS management
- Ovarian stimulation protocol optimisation — improving fertility outcomes while reducing OHSS risk
- Gut microbiome interventions — probiotic and prebiotic therapies targeting the PCOS-microbiome axis
Endometriosis Trials
- Elagolix and relugolix (GnRH antagonists) — oral alternatives to injectable GnRH agonists with fewer side effects
- Dichloroacetate (DCA) — repurposed metabolic drug targeting endometriosis cell metabolism
- Anti-angiogenic agents — starving endometriosis lesions by blocking blood vessel formation
- Immunotherapy approaches — targeting the immune environment that allows endometriosis to thrive
- Non-invasive diagnostic biomarkers — blood and saliva tests to replace laparoscopy for diagnosis
- Robotic and laparoscopic surgical innovations — improving excision outcomes and reducing recurrence
💡 Both conditions take years to diagnose — research is changing that
PCOS takes an average of 2–3 years to diagnose, while endometriosis takes 7–8 years. Both are under the NICE Women's Health Strategy spotlight. UK trials are actively developing faster, non-invasive diagnostic tools — including blood biomarker panels and AI-enhanced imaging. Participating in diagnostic research can help others while potentially accelerating your own diagnosis.
Eligibility Differences
PCOS Trial Criteria
- Rotterdam criteria confirmed (≥ 2 of: oligo/anovulation, hyperandrogenism, polycystic ovaries)
- BMI thresholds common — many metabolic trials target overweight/obese PCOS patients
- Exclusion of other androgen excess disorders (congenital adrenal hyperplasia, androgen-secreting tumours)
- Current medication washout (especially hormonal contraceptives for drug trials)
- Insulin resistance markers may be required for metabolic trials (HOMA-IR, glucose tolerance test)
Endometriosis Trial Criteria
- Diagnosis: laparoscopic confirmation (gold standard) or clinical diagnosis with imaging for some trials
- Endometriosis stage (rASRM I–IV) specified for surgical and drug trials
- Symptom severity: pain scoring (VAS, Biberoglu & Behrman) and quality of life measures
- Hormonal status: some trials require stable or no hormonal treatment
- Fertility intent: some trials separate those trying to conceive from those managing pain
🌸 Endometriosis Trials
Find actively recruiting endometriosis clinical trials across the UK
View Endometriosis Trials