What bloodwork is recommended for the diagnosis and management of Polycystic Ovary Syndrome (PCOS)?

Bloodwork for PCOS

For suspected PCOS, order TSH, prolactin, total or free testosterone (preferably by LC-MS/MS), 2-hour oral glucose tolerance test with 75g glucose load, and fasting lipid panel as your core diagnostic laboratory workup. 1

Core Diagnostic Laboratory Tests

Androgen Assessment

• Measure total testosterone (TT) or free testosterone (FT) as first-line tests using liquid chromatography-tandem mass spectrometry (LC-MS/MS), which shows pooled sensitivity of 74% and specificity of 86% for TT, and superior sensitivity of 89% with specificity of 83% for FT 1
• LC-MS/MS is mandatory as the preferred assay method, demonstrating superior specificity (92%) compared to direct immunoassays (78%), which have higher false-positive rates 1
• If LC-MS/MS is unavailable, calculate Free Androgen Index (FAI) as an alternative 1
• If TT or FT are normal but clinical suspicion remains high, measure androstenedione (A4) and DHEAS as second-line tests, though these have poorer specificity (71% and 67% respectively) 1

Exclusion of Other Endocrine Disorders

• Measure TSH to exclude thyroid disease as a cause of menstrual irregularity 2, 1
• Measure prolactin using morning resting serum levels to exclude hyperprolactinemia 2, 1
• Consider LH and FSH measured between cycle days 3-6, with an LH/FSH ratio >2 suggesting PCOS 1

Metabolic Screening (Critical for Morbidity/Mortality)

• Perform 2-hour oral glucose tolerance test with 75g glucose load to screen for type 2 diabetes and glucose intolerance, as all women with PCOS have demonstrated increased risk 2, 1
• Order fasting lipid panel including total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides to screen for dyslipidemia, which is frequently present in PCOS and contributes to cardiovascular disease risk 2, 1
• Calculate BMI and waist-hip ratio (WHR >0.9 indicates truncal obesity) to assess obesity and central fat distribution 2, 1

Additional Tests When Clinically Indicated

Ovulatory Function Assessment

• Measure mid-luteal phase progesterone (levels <6 nmol/L indicate anovulation) to confirm ovulatory dysfunction 1

Screening for Serious Differential Diagnoses

• Screen for Cushing's syndrome if patient presents with buffalo hump, moon facies, hypertension, abdominal striae, centripetal fat distribution, easy bruising, or proximal myopathies 2, 1
• Consider androgen-secreting tumors if rapid symptom onset, severe hirsutism, or very high testosterone levels (androstenedione >10.0 nmol/L) 2, 1
• Measure DHEAS to rule out non-classical congenital adrenal hyperplasia, especially if elevated 1

Emerging Markers

• Anti-Müllerian Hormone (AMH) ≥35 pmol/L (5 ng/mL) shows high sensitivity (92%) and specificity (97%) for PCOS diagnosis 1

Important Clinical Caveats

The diagnostic accuracy of testosterone varies significantly by which PCOS diagnostic criteria you apply—Rotterdam criteria show higher sensitivity (77%) but lower specificity (83%) compared to NIH criteria (sensitivity 51%, specificity 94%) 1. This means you may get different results depending on your diagnostic framework.

Avoid direct immunoassays for testosterone measurement, as they have substantially lower specificity (78%) compared to LC-MS/MS (92%), leading to false positives that can result in incorrect PCOS diagnoses 1.

The metabolic screening is not optional—women with PCOS have insulin resistance, elevated triglycerides, increased small dense LDL cholesterol, decreased HDL cholesterol, and significantly increased risk for type 2 diabetes and cardiovascular disease 2. These metabolic complications directly impact long-term morbidity and mortality, making glucose tolerance testing and lipid screening essential components of the initial workup 2.