What laboratory tests should be ordered for a 20-year-old patient presenting with symptoms of Polycystic Ovary Syndrome (PCOS)?

Laboratory Tests for a 20-Year-Old with PCOS Symptoms

For a 20-year-old patient presenting with symptoms of Polycystic Ovary Syndrome (PCOS), a comprehensive laboratory evaluation should include hormonal, metabolic, and other relevant tests to confirm diagnosis and assess metabolic risks.

Essential Hormonal Tests

• Total testosterone or bioavailable/free testosterone levels - The most frequently abnormal biochemical marker for PCOS (70% of cases) and best single hormonal indicator 1, 2
• Sex hormone-binding globulin (SHBG) - Often decreased in PCOS, especially with insulin resistance 3
• Luteinizing hormone (LH) and Follicle-stimulating hormone (FSH) - Calculate LH/FSH ratio; ratio >2 suggests PCOS, though sensitivity is only about 41-44% 1, 2
• Prolactin level - To rule out hyperprolactinemia, which can present with similar symptoms 1, 3
• Thyroid-stimulating hormone (TSH) - To exclude thyroid dysfunction 1

Metabolic Evaluation

• Two-hour oral glucose tolerance test with 75g glucose load - Essential for screening for glucose intolerance and diabetes, as recommended by ACOG 1, 3
• Fasting lipid profile - Including total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides to assess cardiovascular risk 1
• Fasting insulin levels - To evaluate insulin resistance; calculate glucose/insulin ratio (ratio >4 suggests insulin resistance) 1, 4

Additional Tests to Consider for Differential Diagnosis

• Androstenedione - Elevated in approximately 53% of PCOS cases; levels >10.0 nmol/L may suggest adrenal/ovarian tumor 1, 2
• Dehydroepiandrosterone sulfate (DHEAS) - To rule out adrenal causes of hyperandrogenism; levels >3800 ng/ml in a 20-year-old suggest non-classical congenital adrenal hyperplasia 1, 3
• 17-hydroxyprogesterone - If non-classical congenital adrenal hyperplasia is suspected 1

Imaging Studies

• Transvaginal ultrasound (if sexually active and acceptable to patient) - Looking for ≥20 follicles per ovary and/or ovarian volume ≥10ml 1, 3
• Transabdominal ultrasound (alternative) - Focus on ovarian volume with threshold of ≥10ml 1, 3

Clinical Considerations and Pitfalls

• Timing of hormonal tests is important - ideally performed between days 3-6 of the menstrual cycle for accuracy 1, 3
• Ultrasound findings alone are insufficient for diagnosis, as polycystic ovarian morphology may be present in up to one-third of reproductive-aged women 3
• Laboratory values should be interpreted in conjunction with clinical signs of hyperandrogenism (hirsutism, acne, alopecia) and menstrual irregularity 1, 3
• Rapid onset of symptoms or marked virilization warrants immediate evaluation for androgen-secreting tumors 3, 5

Interpretation of Results

• PCOS diagnosis requires two of three Rotterdam criteria: hyperandrogenism, ovulatory dysfunction, and polycystic ovaries, after excluding other disorders 3, 5
• Metabolic abnormalities are common - approximately 50-70% of women with PCOS have some degree of insulin resistance 4
• Consider the combined presentation of laboratory findings rather than relying on a single test, as 86% of women with PCOS have elevations in testosterone, androstenedione, or LH, either alone or in combination 2