Etiology
Based on the etiology, hirsutism can be divided into 3 categories: idiopathic, hyperandrogenic, and nonandrogenic.[2]
Idiopathic hirsutism
These women have no identifiable etiology for the excessive hair growth. They have normal androgen levels and regular menstrual cycles. Idiopathic hirsutism accounts for 5% to 15% of all cases. Possible causes include increased androgenic sensitivity in the pilosebaceous unit, increase in conversion of testosterone to dihydrotestosterone, or androgen receptors changing their function.[2]
Hyperandrogenic hirsutism
Hyperandrogenic hirsutism (HH) is the most common category, responsible for over 80% of cases and is usually caused by an overproduction of androgen from the ovaries or adrenal glands. Patients with HH typically have irregular menses, anovulation, infertility, hyperinsulinemia, and have a greater risk of developing endometrial hyperplasia or neoplasia due to the unopposed estrogen.[2] Causes of HH include:
Polycystic ovary syndrome (PCOS): accounts for 72% to 82% of all hirsutism cases
Nonclassic congenital adrenal hyperplasia
Androgen-secreting ovarian tumors
Sertoli-Leydig cell tumors (androblastoma, arrhenoblastoma)
Granulosa-theca cell tumors
Hilus-cell tumors
Ovarian hyperthecosis (a condition with features similar to PCOS, but with more severe androgenization). May occur postmenopausally; the cause is luteinized theca cells, which become hormonally active.
Nonandrogenic hirsutism
Women may develop hirsutism due to certain drugs, such as:[2]
Danazol
Performance-enhancing anabolic steroids
Cyclosporine
Diazoxide
Penicillamine
Interferon
Phenytoin
Cetuximab
Corticosteroids
Androgen creams or patches
Progestins
Estrogen antagonists (e.g., tamoxifen).
Endocrinopathies, such as hypo- or hyperthyroidism, hyperprolactinemia, or Cushing syndrome may also cause hirsutism, though this is uncommon and usually associated with other signs and symptoms of these conditions.
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