What laboratory tests are recommended for a patient suspected of having Polycystic Ovary Syndrome (PCOS)?

Laboratory Tests for Suspected Polycystic Ovary Syndrome (PCOS)

The comprehensive laboratory evaluation for suspected PCOS should include thyroid-stimulating hormone (TSH), prolactin, total testosterone or free testosterone, a two-hour oral glucose tolerance test with 75g glucose load, and fasting lipid profile to properly diagnose PCOS and assess metabolic complications. 1

Core Diagnostic Tests

• Androgen Assessment: Measure total testosterone or bioavailable/free testosterone levels, preferably using mass spectrometry for highest accuracy 1
• Thyroid Function: TSH level to rule out thyroid disease as a cause of menstrual irregularity 2, 1
• Prolactin Level: Morning resting serum prolactin to exclude hyperprolactinemia 2, 1
• Glucose Metabolism: Two-hour oral glucose tolerance test with 75g glucose load (preferred over hemoglobin A1C or fasting glucose alone) 2, 1, 3
• Lipid Profile: Fasting lipid panel including total cholesterol, LDL cholesterol, HDL cholesterol, and triglyceride measurements 2, 1

Tests to Rule Out Other Conditions

• Cushing's Syndrome Screening: Consider if patient presents with buffalo hump, moon facies, hypertension, abdominal striae, central fat distribution, easy bruising, or proximal myopathies 2, 1
• Androgen-Secreting Tumors: Consider if there is rapid onset of symptoms, severe hirsutism, or very high testosterone levels 2, 1
• Non-classic Congenital Adrenal Hyperplasia: Consider measuring DHEAS (Dehydroepiandrosterone sulfate) levels 2, 1
• Primary Ovarian Failure: Check FSH levels if suspected 1

Additional Tests to Consider

• LH and FSH: Measure between days 3-6 of menstrual cycle when possible; an LH/FSH ratio >2 suggests PCOS, though this has lower sensitivity (41-44%) than previously thought 1, 4
• Androstenedione: Consider if testosterone levels are normal but clinical suspicion remains high 1, 4
• Metabolic Assessment: Calculate BMI and waist-hip ratio to identify central obesity, which is associated with worse metabolic outcomes 2, 1

Important Clinical Considerations

• Despite clear guidelines, metabolic screening in PCOS patients is often underutilized in clinical practice, with only 7% of gynecologists ordering the recommended two-hour oral glucose tolerance test 3
• Total testosterone is the most frequently abnormal biochemical marker for PCOS (abnormal in approximately 70% of cases) 4
• The combination of testosterone, androstenedione, or LH measurements may identify up to 86% of PCOS cases 4
• Anti-Müllerian hormone (AMH) should not yet be used as an alternative for the detection of polycystic ovarian morphology or as a single test for the diagnosis of PCOS 2
• Women with PCOS have substantially higher rates of insulin resistance, impaired glucose tolerance, type 2 diabetes, dyslipidemia, and metabolic syndrome compared to women without the condition, making metabolic screening essential 3, 5

Follow-up Testing

• Patients diagnosed with PCOS should undergo repeat screening for glucose intolerance every 2-5 years and lipid screening every 2 years 3
• Regular monitoring of metabolic parameters is particularly important as PCOS is a lifelong condition with increased cardiovascular and metabolic risks 5

Remember that PCOS is a diagnosis of exclusion, and laboratory testing plays a crucial role in both confirming the diagnosis and ruling out other conditions with similar presentations.