Laboratory Testing for PCOS
All women with suspected PCOS require a comprehensive metabolic and hormonal laboratory panel including TSH, prolactin, total or free testosterone, a 2-hour 75-gram oral glucose tolerance test, and a complete fasting lipid profile to establish diagnosis and assess cardiovascular and metabolic risk. 1, 2
Essential Diagnostic Laboratory Tests
Hormonal Assessment for Diagnosis
Thyroid-stimulating hormone (TSH) must be measured to exclude thyroid disease as a cause of menstrual irregularity 1, 2
Prolactin level should be obtained using morning resting serum samples to rule out hyperprolactinemia, which can mimic PCOS 1, 2
Total testosterone or free/bioavailable testosterone is essential for documenting hyperandrogenism, with mass spectrometry preferred for highest accuracy 1, 2
LH and FSH should be measured between cycle days 3-6, with an LH/FSH ratio >2 supporting PCOS diagnosis, though this is no longer required for diagnosis 2, 3
Metabolic Screening (Mandatory for All PCOS Patients)
Because women with PCOS have dramatically increased risk of type 2 diabetes and cardiovascular disease, metabolic screening is not optional but required. 1
2-hour oral glucose tolerance test with 75-gram glucose load is the gold standard for detecting glucose intolerance and type 2 diabetes in PCOS 1, 2
Fasting lipid panel including total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides must be obtained, as dyslipidemia occurs frequently with disproportionately elevated LDL and low HDL 1, 2
Body mass index (BMI) and waist-hip ratio should be calculated to assess obesity and central fat distribution 1, 2
Additional Tests to Exclude Other Diagnoses
When Clinical Suspicion Warrants Further Investigation
DHEAS (dehydroepiandrosterone sulfate) should be measured if non-classical congenital adrenal hyperplasia is suspected, particularly with elevated levels 2
Androstenedione can be measured if testosterone is normal but clinical suspicion remains high, with levels >10.0 nmol/L suggesting adrenal or ovarian tumor 2
Mid-luteal progesterone (measured 7 days before expected menses) confirms anovulation when <6 nmol/L 2
Cushing's syndrome screening is indicated if the patient exhibits buffalo hump, moon facies, hypertension, abdominal striae, central obesity, easy bruising, or proximal muscle weakness 1, 2
Important Caveats and Clinical Pearls
AMH Testing Limitations
Anti-Müllerian hormone (AMH) should NOT be used as a single diagnostic test for PCOS or as an alternative to ultrasound for detecting polycystic ovarian morphology. 1 While AMH levels are elevated in PCOS (threshold ≥35 pmol/L shows 92% sensitivity and 97% specificity), international guidelines explicitly state it should not replace standard diagnostic criteria 1, 2
Timing Considerations
Avoid ultrasound for PCOS diagnosis in women with gynecological age <8 years (within 8 years of menarche) due to high incidence of normal multifollicular ovaries in this population 1
Hormone testing should ideally be performed in the early follicular phase (days 3-6) for LH and FSH 2
Obesity-Specific Recommendations
In women with BMI >30 kg/m², oral glucose tolerance testing is mandatory even if fasting glucose is normal, as 50-70% of PCOS patients have insulin resistance 4, 3
Insulin resistance is associated with elevated triglycerides, increased small dense LDL particles, and decreased HDL cholesterol 1