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

Laboratory Evaluations for Suspected Polycystic Ovary Syndrome (PCOS)

For patients suspected of having PCOS, comprehensive laboratory testing should include thyroid-stimulating hormone, prolactin, total testosterone or free testosterone, a two-hour oral glucose tolerance test, and fasting lipid profile to properly diagnose the condition and assess metabolic complications. 1

Core Diagnostic Laboratory Tests

• Androgen Assessment: Measure total testosterone or bioavailable/free testosterone levels, preferably using mass spectrometry for highest accuracy. If mass spectrometry is unavailable, free androgen index (FAI) can be used as an alternative 1
• Thyroid Function: Thyroid-stimulating hormone (TSH) to rule out thyroid disease as a cause of menstrual irregularity 1
• Prolactin Level: Morning resting serum levels (not postictal) to exclude hyperprolactinemia 1
• Glucose Metabolism: Two-hour oral glucose tolerance test with 75g glucose load (preferred over hemoglobin A1C or fasting glucose alone) 1, 2
• Lipid Profile: Fasting lipid panel including total cholesterol, LDL, HDL, and triglycerides 1

Additional Tests to Consider

• Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH): Measured between days 3-6 of menstrual cycle; LH/FSH ratio >2 may suggest PCOS 1
• Progesterone: Mid-luteal phase levels to confirm anovulation (levels <6 nmol/L indicate anovulation) 1
• Androstenedione: Consider if testosterone levels are normal but clinical suspicion remains high; levels >10.0 nmol/L may indicate adrenal/ovarian tumor 1
• DHEAS (Dehydroepiandrosterone sulfate): To rule out non-classical congenital adrenal hyperplasia, especially with elevated levels (>3800 ng/ml for ages 20-29, >2700 ng/ml for ages 30-39) 1

Metabolic Screening

• Glucose/Insulin Ratio: Fasting morning levels; ratio >4 suggests reduced insulin sensitivity 1
• Body Mass Index (BMI): Calculate to assess obesity, a common feature of PCOS 1
• Waist-Hip Ratio: Measure to identify central obesity (WHR >0.9 indicates truncal obesity) 1

Timing Considerations

• Androgen Testing: Best performed during days 3-6 of menstrual cycle 1
• Glucose Tolerance Testing: Should be performed in all women with PCOS regardless of BMI due to increased risk of type 2 diabetes 1, 2
• Lipid Screening: Should be performed in all women with PCOS due to increased cardiovascular risk 1

Diagnostic Pitfalls to Avoid

• Relying solely on hemoglobin A1C or fasting glucose: These tests may miss impaired glucose tolerance in PCOS patients; the 2-hour OGTT is superior for detecting metabolic abnormalities 2, 3
• Failing to screen for metabolic complications: Despite guidelines, metabolic screening is underutilized in PCOS patients, potentially missing opportunities for early intervention 2
• Delaying evaluation in adolescents: For adolescents, evaluation should be delayed until two years after menarche, and all three Rotterdam criteria should be met before diagnosis 4
• Missing other causes of hyperandrogenism: Marked virilization or rapid symptom onset requires immediate evaluation for androgen-secreting tumors 4

Exclusion of Other Conditions

• Cushing's Syndrome: Screen if patient has buffalo hump, moon facies, hypertension, abdominal striae, central fat distribution, easy bruising, or proximal myopathies 1
• Androgen-Secreting Tumors: Consider if rapid onset of symptoms, severe hirsutism, or very high testosterone levels 1
• Congenital Adrenal Hyperplasia: Consider if elevated DHEAS levels 1
• Acromegaly: Assess if coarse facial features, enlarged hands/feet present 1
• Primary Ovarian Failure: Check FSH levels 1

By following this comprehensive laboratory evaluation approach, clinicians can accurately diagnose PCOS and identify associated metabolic complications that require management to reduce long-term health risks 5, 6.