Causes of Hirsutism
The primary causes of hirsutism include polycystic ovary syndrome (PCOS), idiopathic hirsutism, non-classical congenital adrenal hyperplasia, androgen-secreting tumors, and other endocrine disorders that lead to androgen excess. 1
Common Causes of Hirsutism
Polycystic Ovary Syndrome (PCOS)
PCOS is the most common cause of hirsutism, affecting approximately 10-13% of women globally and accounting for 70-80% of hirsutism cases 1. Key features include:
- Hyperandrogenism (clinical or biochemical)
- Ovulatory dysfunction (oligo- or anovulation)
- Polycystic ovaries on ultrasound
- Insulin resistance and hyperinsulinemia contributing to ovarian theca stromal cell hyperactivity 1
- Prevalence is higher (10-25%) in women with temporal lobe epilepsy 1
Idiopathic Hirsutism
- Accounts for approximately 5-17% of hirsutism cases, depending on ethnicity and geographic area 2
- Defined as hirsutism with normal ovulatory cycles and normal androgen levels
- May be due to increased sensitivity of hair follicles to normal androgen levels 3
Non-Classical Congenital Adrenal Hyperplasia
- Affects approximately 1-8% of women with hirsutism 2
- Most commonly due to 21-hydroxylase deficiency
- Can cause modest elevation of testosterone levels 1
Less Common Causes
Androgen-Secreting Tumors
- Ovarian or adrenal in origin
- Rare but potentially life-threatening 2
- Suspect when:
Cushing's Syndrome
- Presents with:
- Weight gain, proximal muscle weakness
- Hypertension, psychiatric disturbances
- Hirsutism, centripetal obesity
- Purple striae, buffalo hump
- Supraclavicular fat pad enlargement
- Hyperglycemia and hypokalemia 1
Hyperandrogenic-Insulin-Resistant Acanthosis Nigricans Syndrome
- Affects approximately 3% of hyperandrogenic women 2
- Characterized by insulin resistance and dark, velvety skin patches
Other Endocrine Disorders
- Hyperprolactinemia: Can cause hirsutism through indirect effects on androgen metabolism 2, 5
- Acromegaly: Excess growth hormone can lead to hirsutism 2
- Hyperaldosteronism: Rarely causes hirsutism, but can present with hypertension and hypokalemia 1
- Thyroid dysfunction: Can contribute to menstrual irregularities and hair changes 1
Medication-Induced Hirsutism
- Certain medications can cause hirsutism:
- Anabolic steroids
- Danazol
- Valproate (can increase testosterone levels) 1
- Cyclosporine
- Minoxidil
Diagnostic Approach
Key Laboratory Tests
First-line androgen tests 1:
- Total testosterone (TT)
- Free testosterone (FT) - calculated using equilibrium dialysis or FAI
Second-line androgen tests if initial tests are normal:
- Androstenedione (A4)
- Dehydroepiandrosterone sulfate (DHEAS)
Additional testing based on clinical suspicion:
- Fasting glucose/insulin ratio (for insulin resistance)
- Thyroid function tests
- Prolactin levels
- 17-hydroxyprogesterone (for non-classical adrenal hyperplasia)
- Cortisol studies (if Cushing's syndrome suspected)
Imaging
- Pelvic ultrasound: To identify polycystic ovaries or ovarian tumors
- Adrenal imaging: If adrenal pathology suspected based on DHEAS levels
Clinical Pearls and Pitfalls
Diagnostic pitfall: Relying solely on testosterone levels may miss cases of hyperandrogenism. Consider measuring multiple androgens, especially in women with normal testosterone but clinical signs of androgen excess 1.
Laboratory pitfall: Direct immunoassays for androgens are less accurate than liquid chromatography with tandem mass spectrometry (LC-MS/MS), which should be used when available 1.
Clinical pearl: Hirsutism severity doesn't always correlate with androgen levels due to variations in hair follicle sensitivity to androgens 3.
Warning sign: Rapidly progressive hirsutism with virilization strongly suggests an androgen-secreting tumor and requires urgent evaluation 4.
Treatment consideration: For women with hirsutism requiring antiandrogen therapy, ensure safe non-hormonal contraception is in place to prevent fetal male pseudohermaphroditism in case of pregnancy 5.