What laboratory and imaging studies should be performed to evaluate suspected polycystic ovary syndrome?

Laboratory and Imaging Workup for Suspected PCOS

All women suspected of having PCOS should undergo hormonal testing (total testosterone via LC-MS/MS, TSH, prolactin), metabolic screening (2-hour 75g oral glucose tolerance test and fasting lipid panel), and transvaginal ultrasound with ≥8 MHz transducer to count follicles and measure ovarian volume. 1, 2, 3

Essential Laboratory Tests

Hormonal Evaluation

• Total testosterone measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) is the single best initial biochemical marker, demonstrating 74% sensitivity and 86% specificity for detecting hyperandrogenism. 1
• Calculated free testosterone using the Vermeulen equation shows the highest sensitivity at 89% with 83% specificity when calculated from high-quality total testosterone and SHBG measurements. 1
• TSH measurement is required to exclude thyroid disease as a cause of menstrual irregularities. 1, 2, 3
• Morning fasting prolactin should be obtained to rule out hyperprolactinemia; women with PCOS have a 3.15-fold increased risk of elevated prolactin compared to women without PCOS. 1
• 17-hydroxyprogesterone should be measured to exclude non-classic congenital adrenal hyperplasia. 2

Metabolic Screening (Required Regardless of BMI)

• 2-hour oral glucose tolerance test using 75g glucose load must be performed in all women with suspected PCOS to detect type 2 diabetes or impaired glucose tolerance, because insulin resistance occurs independently of body weight. 1, 2, 3
• Fasting lipid profile (total cholesterol, LDL, HDL, triglycerides) is required to assess cardiovascular risk, as women with PCOS have markedly higher prevalence of dyslipidemia. 1, 2, 3
• Serum 25-hydroxy-vitamin D should be measured, as deficiency is present in 67-85% of women with PCOS. 1

Imaging Studies

Transvaginal Ultrasound (First-Line)

• Transvaginal ultrasound with ≥8 MHz transducer frequency is the optimal imaging approach for sexually active adults. 1, 2, 3
• ≥20 follicles per ovary (2-9mm diameter) is the gold standard ultrasonographic marker with 87.64% sensitivity and 93.74% specificity. 1, 2, 3
• Ovarian volume >10 mL serves as an alternative diagnostic threshold when accurate follicle counting is difficult. 1, 2, 3
• The ultrasound must be performed in the absence of corpus luteum, cysts, or dominant follicles ≥10mm. 2, 3

When Ultrasound Should NOT Be Used

• Do not use ultrasound for diagnosis in adolescents <8 years post-menarche due to poor specificity and high false-positive rates from physiologically normal multifollicular ovaries. 1, 2
• Ultrasound is not mandatory when both irregular cycles AND clinical/biochemical hyperandrogenism are already documented, though it helps define the complete phenotype. 2

Alternative Imaging Options

• Transabdominal ultrasound may be used for non-sexually active patients, focusing on ovarian volume ≥10 mL, as reliable follicle counting is limited with this approach. 2, 3
• MRI pelvis without contrast can be considered in obese patients when ultrasound cannot adequately visualize the ovaries. 2, 3

Tests to Exclude Mimicking Conditions

Essential Exclusion Testing

• Dexamethasone suppression test if clinical features suggest Cushing's syndrome (buffalo hump, moon facies, central obesity, easy bruising, proximal myopathy). 1, 2
• Evaluate for androgen-secreting tumors if rapid onset of severe virilization with marked clitoromegaly or voice deepening is present. 1, 3
• Screen for acromegaly when compatible clinical signs are identified. 1

Physical Examination Findings to Document

• Clinical signs of hyperandrogenism: hirsutism distribution, acne, male-pattern balding, clitoromegaly. 1, 3
• Markers of insulin resistance: BMI, waist-to-hip ratio, acanthosis nigricans on neck, axillae, under breasts, or vulva. 1, 2, 3
• Blood pressure measurement at least annually to screen for hypertension. 1
• Pelvic examination to detect ovarian enlargement. 1, 3

Critical Pitfalls to Avoid

• Do not use anti-Müllerian hormone (AMH) levels as a substitute for ultrasound or as a standalone diagnostic test, as assay standardization and validated cut-offs are lacking. 1, 2, 3
• Do not diagnose PCOS based on ultrasound findings alone, as polycystic ovarian morphology is present in up to one-third of reproductive-aged women without PCOS. 1, 3
• Remove hormonal contraception before testing, as progestin-only implants and oral contraceptives suppress the hypothalamic-pituitary-ovarian axis and make hormone levels unreliable. 1
• Recognize increased endometrial cancer risk due to chronic anovulation, obesity, hyperinsulinemia, and reduced SHBG, requiring appropriate follow-up. 1, 2

Additional Screening Considerations

• Formal screening for anxiety, depression, body-image concerns, and eating disorders should be incorporated into routine care, as these conditions are highly prevalent in PCOS. 1
• Annual blood pressure monitoring is required given elevated cardiovascular risk. 1
• Body weight tracking every 6-12 months, as even 5% weight loss can improve metabolic and reproductive abnormalities. 1