Initial Laboratory Workup for Hirsutism in Women
The initial laboratory workup for hirsutism should include total testosterone (TT) and free testosterone (FT) as first-line tests, preferably measured by liquid chromatography with tandem mass spectrometry (LC-MS/MS), with second-line testing including androstenedione (A4) and DHEAS if initial androgens are not elevated. 1
First-Line Androgen Testing
The 2023 International PCOS Guidelines, informed by a comprehensive meta-analysis of 2,857 participants, established the following hierarchy for androgen measurement 1:
- Total testosterone (TT) should be measured as a primary test, with pooled sensitivity of 0.74 and specificity of 0.86 for detecting biochemical hyperandrogenism 1
- Free testosterone (FT) should be measured, showing superior sensitivity of 0.89 compared to other androgens 1
- Calculated free testosterone (cFT) should be assessed by equilibrium dialysis, ammonium sulfate precipitation, or calculated using the free androgen index (FAI) when direct measurement is unavailable 1
- LC-MS/MS methodology is strongly preferred over immunoassays, demonstrating superior specificity for measuring TT (0.92 vs 0.78), cFT, and FAI 1
The FAI demonstrates good diagnostic accuracy with sensitivity of 0.78 and specificity of 0.85, making it a reasonable alternative when mass spectrometry is unavailable 1
Second-Line Androgen Testing
If TT or FT are not elevated, additional androgens should be measured, though clinicians should recognize their inferior diagnostic performance 1:
- Androstenedione (A4) has sensitivity of 0.75 but notably poor specificity of 0.71, and should be checked to rule out adrenal or ovarian tumors (abnormal if >10.0 nmol/L) 1
- DHEAS demonstrates the poorest performance with sensitivity of 0.75 and specificity of only 0.67, but helps identify adrenal androgen production 1, 2
Essential Screening Tests Beyond Androgens
The workup must exclude other endocrine disorders that can present with hirsutism 1, 2:
- Thyroid-stimulating hormone (TSH) to rule out thyroid disease 2
- Prolactin (morning resting levels, not postictal) to exclude hyperprolactinemia (abnormal if >20 μg/L) 1, 2
- LH and FSH measured between cycle days 3-6 (average of three measurements 20 minutes apart), with LH/FSH ratio >2 suggesting PCOS 1
- Mid-luteal progesterone to assess ovulation, with levels <6 nmol/L indicating anovulation 1
Metabolic Screening
Given the strong association between hyperandrogenism and metabolic dysfunction 2:
- Fasting glucose and 2-hour oral glucose tolerance test to screen for diabetes and insulin resistance (abnormal if fasting glucose >7.8 mmol/L) 1, 2
- Fasting lipid panel to assess cardiovascular risk 2
- Glucose/insulin ratio with ratio >4 suggesting reduced insulin sensitivity 1
Imaging Studies
- Pelvic ultrasound (transvaginal preferred over transabdominal, performed days 3-9 of cycle) 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 Clinical Caveats
Timing matters: Blood samples for testosterone should be drawn on cycle days 3-6, while progesterone requires mid-luteal phase timing 1. The 2023 guidelines emphasize that LC-MS/MS has superior accuracy compared to direct immunoassays across all androgen measurements 1.
Red flags requiring urgent evaluation: Very high testosterone levels (>2.5 nmol/L) or rapidly developing symptoms should prompt immediate investigation for androgen-secreting tumors 1, 2. Markedly elevated DHEAS warrants evaluation for adrenal pathology 1.
Common pitfall: Approximately 5-15% of hirsute women have "idiopathic hirsutism" with normal ovulatory function and androgen levels, so normal laboratory results do not exclude the diagnosis 3, 4. The modified Ferriman-Gallwey score should guide clinical assessment regardless of laboratory findings 4.
Ethnic considerations: Hirsutism prevalence and androgen levels vary by ethnicity, with Asian women potentially showing less hirsutism despite androgen excess 3, 4. PCOS remains the most common cause in 70-80% of cases, followed by idiopathic hirsutism (5-15%) and non-classic adrenal hyperplasia (1-10% depending on ethnicity) 3, 4.