Laboratory Evaluation for PCOS
Order total testosterone (or free/bioavailable testosterone), TSH, prolactin, a 2-hour oral glucose tolerance test with 75g glucose load, and a fasting lipid panel; also obtain a pregnancy test to exclude pregnancy before initiating any treatment. 1
Core Diagnostic Tests
Androgen Assessment
- Measure total testosterone as the primary androgen marker, which has the highest diagnostic sensitivity (70% abnormal in PCOS patients) compared to other hormonal tests 2
- Total testosterone can be measured by direct immunoassay (sensitivity 74%, specificity 78%) or preferably by LC-MS/MS (sensitivity 71%, specificity 92%) for better accuracy 1
- Free or bioavailable testosterone are acceptable alternatives to total testosterone for documenting hyperandrogenism 1
- Calculated free testosterone (cFT) demonstrates excellent diagnostic performance with 89% sensitivity and 83% specificity 1
Exclusion of Other Disorders
- TSH level to exclude thyroid disease, which can mimic PCOS symptoms 1
- Prolactin level to rule out hyperprolactinemia, another cause of menstrual irregularity and androgen excess 1
- Pregnancy test is essential before starting any hormonal treatment or making the diagnosis 3
Metabolic Screening Tests
Glucose Assessment
- Fasting glucose followed by 2-hour glucose level after 75g oral glucose load is recommended by ACOG for all women with PCOS due to increased diabetes risk 1
- This screening is based on consensus and expert opinion recognizing the substantially elevated risk of type 2 diabetes and glucose intolerance in PCOS 1
Lipid Screening
- Fasting lipid panel including total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides should be obtained in all women with PCOS 1
- This recommendation is based on good and consistent scientific evidence showing frequent dyslipidemia in PCOS patients 1
- Women with PCOS commonly have elevated LDL cholesterol, low HDL cholesterol, and elevated triglycerides due to insulin resistance 1
Optional Additional Tests
When to Consider Additional Androgen Testing
- Androstenedione can be added if initial testosterone is normal but clinical suspicion remains high (53% abnormal in PCOS) 2
- The combination of testosterone, androstenedione, or LH (either alone or together) identifies 86% of PCOS cases 2
- DHEAS has limited diagnostic value as it does not differ significantly between PCOS and control groups 2
Tests to Avoid or Use Cautiously
- LH/FSH ratio should NOT be used as a primary diagnostic criterion due to low sensitivity (only 35-44% abnormal in confirmed PCOS cases) 2
- While historically popular, the LH/FSH ratio >2:1 or >3:1 has poor diagnostic performance and should be abandoned as a biochemical criterion 2
- Pelvic ultrasound for polycystic ovarian morphology is not required for diagnosis in adults when clinical and biochemical criteria are met 4
- Anti-Müllerian hormone (AMH) should not be used for diagnosis, though it may have emerging roles as a biomarker 5, 6
Important Caveats
Timing and Interpretation
- All hormone measurements should be obtained in the early follicular phase (days 3-5) in women with any menstrual cycles, or at any time in amenorrheic women 2
- Normal ranges must be precisely defined for each laboratory's specific assay method, as absolute values differ significantly between assay techniques 2
- LC-MS/MS methods for testosterone measurement are more specific than direct immunoassays, though both are acceptable 1
Clinical Context
- The diagnosis of PCOS remains primarily clinical, based on hyperandrogenism and ovulatory dysfunction; laboratory tests support but do not make the diagnosis 3, 7
- Laboratory evaluation serves two purposes: confirming hyperandrogenism and excluding other disorders that mimic PCOS (thyroid disease, hyperprolactinemia, Cushing's syndrome, congenital adrenal hyperplasia, androgen-secreting tumors) 1
- If clinical features suggest Cushing's syndrome (buffalo hump, moon facies, abdominal striae, easy bruising), additional screening for this disorder is warranted 1