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

Laboratory Evaluations for Suspected PCOS

For patients suspected of having Polycystic Ovary Syndrome (PCOS), a comprehensive laboratory evaluation should include measurements of LH, FSH, total testosterone, free testosterone, prolactin, TSH, fasting glucose/insulin, and lipid profile, with timing of hormone tests between days 3-6 of the menstrual cycle. 1

Core Laboratory Tests

Hormone Panel (Days 3-6 of Menstrual Cycle)

• Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH)

  • LH/FSH ratio >2 suggests PCOS 2
  • Measurement should be based on an average of three estimations taken 20 minutes apart 2

• Androgen Assessment

  • Total Testosterone (sensitivity 74%, specificity 86%) 1
  • Free Testosterone (sensitivity 89%, specificity 83%) 1
  • Free Androgen Index (FAI) (sensitivity 78%, specificity 85%) 1
  • Androstenedione (sensitivity 75%, specificity 71%) 1
  • DHEAS (sensitivity 75%, specificity 67%) 1

• Additional Hormones

  • Prolactin (morning resting levels, not postictal) 2
  • Estradiol 1
  • Progesterone (mid-luteal phase) - levels <6 nmol/l indicate anovulation 2

Metabolic Assessment

• Glucose Metabolism

  • Fasting glucose/insulin ratio (ratio >4 suggests reduced insulin sensitivity) 2
  • 2-hour oral glucose tolerance test with 75g glucose load 1
  • HbA1c 1

• Lipid Profile

  • Total cholesterol, LDL, HDL, triglycerides 1

Tests to Exclude Other Conditions

• Thyroid-stimulating hormone (TSH) - to rule out thyroid dysfunction 1
• 17-hydroxyprogesterone - to rule out non-classical congenital adrenal hyperplasia 1
• Overnight dexamethasone suppression test or 24-hour urinary free cortisol - to rule out Cushing's syndrome 1

Imaging

• Transvaginal ultrasound (preferred method if sexually active and acceptable to patient) 1
  • Diagnostic threshold: ≥20 follicles (2-9mm) per ovary or ovarian volume ≥10ml 1
  • Should be performed between days 3-9 of the cycle 2
  • Not recommended for women <8 years after menarche due to high incidence of multi-follicular ovaries 1

Practical Considerations

Timing of Tests

• Hormone evaluations (FSH, LH, estradiol, testosterone) should be measured between days 3-6 of the menstrual cycle 1
• Progesterone should be measured during mid-luteal phase (approximately day 21 of a 28-day cycle) 1

Test Interpretation Pitfalls

• Age and ethnicity affect normal reference ranges for androgens 1
• Laboratory values must be interpreted in context of clinical presentation 1
• Polycystic ovaries on ultrasound alone is insufficient for diagnosis, particularly in adolescents <8 years post-menarche 1

Common Testing Patterns

• Studies show variable testing patterns in primary care, with endocrine testing (estradiol, LH, FSH, testosterone, SHBG) typically peaking in the weeks before diagnosis 3
• Metabolic testing (glucose, lipids) is often underutilized after diagnosis 3

Clinical Correlation

Laboratory results should be interpreted alongside clinical features:

• Menstrual irregularity (oligomenorrhea or amenorrhea) 2
• Hirsutism, acne, male-pattern hair loss 1
• Acanthosis nigricans (sign of insulin resistance) 1
• Body mass index (BMI) and waist-hip ratio 1

Remember that PCOS is a diagnosis of exclusion requiring at least two of three criteria: chronic anovulation, hyperandrogenism (clinical or biochemical), and polycystic ovaries, after ruling out other relevant disorders 1.