What laboratory tests are indicated for a female presenting with hirsutism (excessive facial hair)?

Laboratory Tests for Females with Hirsutism

For females presenting with hirsutism (excessive facial hair), laboratory testing should include free and total testosterone, dehydroepiandrosterone sulfate (DHEA-S), androstenedione, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) to identify the underlying cause. 1, 2

Initial Laboratory Evaluation

The following tests should be ordered for a female with hirsutism:

First-line Testing:

• Free and total testosterone - Most consistent finding in hirsutism is elevated free testosterone 3
• DHEA-S - To evaluate for adrenal hyperandrogenism 1, 2
• Androstenedione - Additional androgen marker 2
• LH and FSH - To assess for polycystic ovary syndrome (PCOS) 2
• TSH and free T4 - To rule out thyroid dysfunction 2
• Prolactin - To rule out hyperprolactinemia 2, 4

Second-line Testing (Based on Clinical Suspicion):

• 17-hydroxyprogesterone - To evaluate for non-classic congenital adrenal hyperplasia 4
• Morning cortisol - If Cushing syndrome is suspected 5

When to Order These Tests

Laboratory testing is indicated in females with:

• Moderate to severe hirsutism
• Any degree of hirsutism with:
  • Rapid onset or progression (within 3-6 months)
  • Menstrual irregularities
  • Infertility
  • Central obesity
  • Acanthosis nigricans
  • Clitoromegaly or other signs of virilization 5, 4

Interpretation of Results

PCOS Pattern:

• LH:FSH ratio >2 2
• Mildly elevated testosterone
• Normal to slightly elevated DHEA-S

Adrenal Hyperandrogenism:

• Elevated DHEA-S
• Elevated 17-hydroxyprogesterone (in congenital adrenal hyperplasia)

Ovarian or Adrenal Tumor (Rare):

• Markedly elevated testosterone (>200 ng/dL) or DHEA-S (>700 μg/dL)
• Rapid onset of symptoms with virilization 5

Idiopathic Hirsutism:

• Normal hormone levels
• Regular ovulatory cycles 6

Clinical Pearls

• Timing matters: Hormonal testing should ideally be performed in the early follicular phase (days 3-6) of the menstrual cycle for accurate results 2
• Free testosterone is more sensitive than total testosterone for detecting hyperandrogenism, as testosterone-estradiol binding globulin levels are often depressed in hirsute women 3
• PCOS and idiopathic hyperandrogenism account for >85% of hirsutism cases 5
• Rapid onset of hirsutism (over a few months) or signs of virilization warrant urgent evaluation for androgen-secreting tumors 5

Common Pitfalls to Avoid

• Relying solely on total testosterone without measuring free testosterone
• Assuming regular menses excludes ovulatory dysfunction (up to 40% of eumenorrheic hirsute women are anovulatory) 6
• Failing to consider non-androgen causes of hirsutism such as medications, thyroid disorders, or Cushing syndrome 5
• Not accounting for the effect of oral contraceptives on hormone levels (may suppress androgen levels)

By following this systematic approach to laboratory testing in females with hirsutism, clinicians can identify the underlying cause and implement appropriate treatment strategies to address both the cosmetic concerns and any associated health issues.