What laboratory tests are recommended for women presenting with hirsutism?

Laboratory Workup for Hirsutism in Women

Measure total testosterone and free testosterone as first-line tests using LC-MS/MS methodology, followed by TSH and prolactin to exclude thyroid disease and hyperprolactinemia. 1

First-Line Androgen Testing

• Total testosterone (TT) and free testosterone (FT) are the essential first-line tests, with TT showing pooled sensitivity of 0.74 and specificity of 0.86, while FT demonstrates superior sensitivity of 0.89 for detecting biochemical hyperandrogenism. 1

• LC-MS/MS methodology is strongly preferred over immunoassays for measuring testosterone due to superior specificity and accuracy. 1, 2

• Calculated free testosterone (cFT) or free androgen index (FAI) should be used when direct FT measurement is unavailable, with FAI showing good diagnostic accuracy (sensitivity 0.78, specificity 0.85). 1

• Blood samples for testosterone must be drawn on cycle days 3-6 in the early follicular phase for accurate interpretation. 1

Essential Screening Tests to Exclude Other Causes

• TSH should be measured to rule out thyroid disease as a cause of hirsutism. 3, 1, 2

• Prolactin levels should be checked to exclude hyperprolactinemia, with abnormal levels defined as >20 μg/L. 3, 1, 2

• LH and FSH should be measured between cycle days 3-6, with an LH/FSH ratio >2 suggesting polycystic ovary syndrome. 1

• Mid-luteal progesterone should be assessed to evaluate ovulation status, with levels <6 nmol/L indicating anovulation. 1

Second-Line Androgen Testing (If Initial Tests Normal)

• Androstenedione (A4) should be measured if TT or FT are not elevated, with sensitivity of 0.75 and specificity of 0.71, and abnormal levels >10.0 nmol/L suggesting adrenal or ovarian tumors. 1

• DHEAS should be measured to identify adrenal androgen production, using age-specific cutoffs (>3800 ng/mL for ages 20-29, >2700 ng/mL for ages 30-39), with markedly elevated levels warranting evaluation for non-classical congenital adrenal hyperplasia or adrenal pathology. 1, 2

Metabolic Screening (Essential for PCOS Evaluation)

• Fasting glucose followed by 2-hour oral glucose tolerance test with 75-gram glucose load should be performed to screen for diabetes and insulin resistance, with abnormal fasting glucose defined as >7.8 mmol/L. 3, 1, 2

• Fasting lipid panel including total cholesterol, LDL, HDL, and triglycerides should be assessed to evaluate cardiovascular risk. 3, 1, 2

• Glucose/insulin ratio should be calculated, with a ratio >4 suggesting reduced insulin sensitivity. 1

Imaging Studies

• Pelvic ultrasound (transvaginal preferred) should be performed if hormonal tests suggest PCOS or to rule out ovarian pathology, looking for >10 peripheral cysts of 2-8 mm diameter with thickened ovarian stroma. 1

Critical Red Flags Requiring Urgent Investigation

• Very high testosterone levels (>2.5 nmol/L) or rapidly developing symptoms should prompt immediate investigation for androgen-secreting tumors of the ovary or adrenal gland. 1, 2

• Coexisting signs of Cushing's syndrome (buffalo hump, moon facies, hypertension, abdominal striae, centripetal fat distribution, easy bruising, or proximal myopathies) should trigger screening for this disorder. 3

• Acanthosis nigricans should raise concern for associated insulinoma or malignancy, particularly gastric adenocarcinoma. 3

Common Pitfalls to Avoid

• Avoid using direct immunoassays for testosterone measurement as they lack the specificity of LC-MS/MS, particularly at the low concentrations seen in women. 1, 2

• Do not rely solely on total testosterone when sex hormone binding globulin is low, as free testosterone may be elevated even when total testosterone appears normal. 1

• Ensure proper timing of blood draws - testosterone on cycle days 3-6 and progesterone in the mid-luteal phase - as improper timing invalidates results. 1