What are the causes of postmenopausal hirsutism in women after menopause?

Causes of Postmenopausal Hirsutism

Postmenopausal hirsutism results from either relative androgen excess due to declining estrogen levels during menopause, or absolute androgen excess from ovarian/adrenal pathology, with polycystic ovary syndrome being the most common cause, though androgen-secreting tumors must be urgently excluded when testosterone exceeds 5 nmol/L or virilization is present. 1

Primary Etiologies

Benign Causes (Most Common)

• Polycystic ovary syndrome (PCOS) is the most common cause of postmenopausal hyperandrogenism, manifesting as mild to moderate hirsutism 1
• Relative androgen excess occurs during menopausal transition when estrogen levels decline but androgen production continues, creating an unfavorable androgen-to-estrogen ratio 1, 2
• Idiopathic hirsutism presents with normal androgen levels but increased hair growth in androgen-dependent areas 3
• Idiopathic hyperandrogenemia shows elevated androgens without identifiable pathology 3
• Ovarian hyperthecosis causes virilizing symptoms through diffuse ovarian stromal androgen production 1, 2

Iatrogenic Causes

• Endocrine therapy-induced hirsutism can occur in postmenopausal women receiving aromatase inhibitors for breast cancer, causing excessive hair growth in androgen-dependent body areas 4
• Drug-induced hirsutism from medications including androgens, anabolic steroids, danazol, and certain progestins 3

Adrenal Disorders

• Congenital adrenal hyperplasia due to 21-hydroxylase deficiency can present or worsen postmenopausally 3
• Cushing syndrome causes androgen excess along with characteristic cushingoid features 3
• Androgen-secreting adrenal tumors (potentially malignant) require urgent evaluation when suspected 1, 2

Ovarian Tumors (Critical to Exclude)

• Androgen-secreting ovarian tumors including Sertoli-Leydig cell tumors, granulosa cell tumors, and hilus cell tumors are rare but potentially malignant 3, 1, 5
• Benign ovarian tumors such as serous cystadenofibroma can rarely cause androgen excess and hirsutism 5
• Ovarian tumors account for approximately 1% of hirsutism cases but carry significant morbidity/mortality risk if malignant 5

Other Endocrinopathies

• Acromegaly from growth hormone excess 3
• Hyperprolactinemia disrupting the hypothalamic-pituitary-gonadal axis 3
• Thyroid dysfunction (both hypothyroidism and hyperthyroidism) 3

Critical Red Flags Requiring Urgent Evaluation

Testosterone >5 nmol/L is associated with virilization and mandates prompt investigation to rule out androgen-producing tumors as the first priority. 1

• Rapid onset of symptoms suggests tumor rather than benign etiology 2
• Virilization signs including clitoromegaly, deepening voice, increased muscle mass, or male-pattern baldness indicate severe androgen excess 1, 2
• Severe degree of androgen elevation on laboratory testing 2

Diagnostic Approach

Initial Laboratory Evaluation

• Serum testosterone measurement by tandem mass spectrometry is the first step, providing critical information on degree of androgen excess 1
• Measure DHEA-sulfate to assess adrenal contribution 1, 5
• Check sex hormone-binding globulin (SHBG), as low levels increase free androgen bioavailability 5
• Evaluate thyroid function (TSH, free T4) to exclude thyroid disorders 4

Imaging Studies

• Transvaginal ultrasound or MRI for ovarian evaluation when ovarian source suspected 1, 5
• Computed tomography or MRI of adrenals when adrenal tumor suspected based on elevated DHEA-sulfate 1
• Imaging is essential when testosterone exceeds 5 nmol/L to localize tumor source 1

Associated Metabolic Consequences

• Postmenopausal hyperandrogenism associates with abdominal obesity, insulin resistance, and type 2 diabetes 1
• Long-term cardiovascular morbidity and mortality risks remain incompletely defined but warrant monitoring 2
• Androgen excess may have negative long-term health consequences requiring detection and treatment 6

Common Pitfalls

• Failing to measure testosterone by mass spectrometry rather than immunoassay, which lacks accuracy at postmenopausal ranges 1
• Dismissing mild hirsutism as "normal aging" without excluding underlying pathology 6
• Delaying imaging when testosterone is significantly elevated, risking delayed cancer diagnosis 1, 2
• Not recognizing that benign ovarian tumors can cause androgen excess and associated conditions like endometrial cancer 5