What laboratory tests are recommended for the diagnosis and management of Polycystic Ovary Syndrome (PCOS)?

Laboratory Testing for PCOS

All women with suspected PCOS should undergo a comprehensive laboratory evaluation including androgen testing (total or free testosterone via LC-MS/MS), TSH, prolactin, 2-hour oral glucose tolerance test with 75g glucose load, and fasting lipid panel to establish the diagnosis and screen for metabolic complications. 1

Core Diagnostic Laboratory Tests

Androgen Assessment

• Measure total testosterone (TT) and free testosterone (FT) as first-line tests using liquid chromatography-tandem mass spectrometry (LC-MS/MS), which demonstrates superior specificity (92%) compared to direct immunoassays (78%) 1
• Total testosterone shows pooled sensitivity of 74% and specificity of 86%, while free testosterone demonstrates superior sensitivity of 89% with specificity of 83% 1
• If TT or FT are not elevated but clinical suspicion remains high, measure androstenedione (sensitivity 75%, specificity 71%) and DHEAS (sensitivity 75%, specificity 67%) as second-line tests 1
• Important caveat: Total testosterone is abnormal in only 70% of women with confirmed PCOS, meaning 30% have normal testosterone levels despite having the condition 1

Exclusion of Other Endocrine Disorders

• Measure TSH to exclude thyroid disease as a cause of menstrual irregularity 2, 1
• Measure prolactin level (using morning resting serum levels) to exclude hyperprolactinemia 2, 1
• Measure 17-hydroxyprogesterone to exclude congenital adrenal hyperplasia 3
• Consider dexamethasone suppression test if patient has buffalo hump, moon facies, hypertension, abdominal striae, central fat distribution, easy bruising, or proximal myopathies to screen for Cushing's syndrome 2, 3

Metabolic Screening (Critical for Long-term Outcomes)

Glucose Metabolism

• Perform 2-hour oral glucose tolerance test with 75g glucose load to screen for type 2 diabetes and glucose intolerance in all women with PCOS, regardless of BMI 2, 1, 3
• This recommendation is based on the demonstrated increased risk of diabetes in PCOS patients 2

Lipid Assessment

• Obtain fasting lipid panel including total cholesterol, LDL cholesterol, HDL cholesterol, and triglyceride measurements 2, 1
• Women with PCOS frequently have dyslipidemia, including elevated LDL cholesterol, elevated triglycerides, and decreased HDL cholesterol due to insulin resistance 2

Anthropometric Measurements

• Calculate body mass index (BMI) to assess obesity 2, 1, 3
• Measure waist-hip ratio to identify central obesity, with WHR >0.9 indicating truncal obesity 1, 3

Additional Tests to Consider

Ovulatory Function Assessment

• Measure LH and FSH between days 3-6 of menstrual cycle, with LH/FSH ratio >2 suggesting PCOS (though this is abnormal in only 35-44% of women with PCOS, making it a poor diagnostic marker) 1
• Measure progesterone in mid-luteal phase to confirm anovulation, with levels <6 nmol/L indicating anovulation 1

Insulin Resistance Markers

• Consider measuring fasting glucose/insulin ratio, with a ratio >4 suggesting reduced insulin sensitivity 1

Anti-Müllerian Hormone (AMH)

• AMH should NOT be used as an alternative for detecting polycystic ovarian morphology or as a single test for PCOS diagnosis, though elevated levels (≥35 pmol/L or 5 ng/mL) show high sensitivity (92%) and specificity (97%) 1, 3
• AMH is a potential future surrogate marker but requires additional validation 1

Critical Clinical Pitfalls

The most important pitfall is assuming normal laboratory values exclude PCOS. A woman can be diagnosed with PCOS based solely on clinical hyperandrogenism (hirsutism, acne, or alopecia) plus irregular menstrual cycles, without any abnormal laboratory values, per the Rotterdam criteria 1. Clinical assessment including menstrual pattern, physical signs of hyperandrogenism, and ultrasound morphology remains paramount and can establish the diagnosis even when all laboratory tests return normal 1.

All women with PCOS should be screened for metabolic dysfunction regardless of body weight, as insulin resistance occurs independently of BMI and affects both lean and overweight women 3.