Table 1 Causes of prepubertal gynecomastia[1–4, 10, 12]

Idiopathic

No known cause

Exposure to exogenous estrogens

• Dermal and hair preparations (e.g. lavender and tea tree oils)

• Milk and meat of cows treated with estrogens

Illness

• Liver disease (e.g. cirrhosis)

• Renal failure

• Thyrotoxicosis

• Malnutrition

Neoplasia

• Adrenal

• Testicular

Congenital adrenal hyperplasia

• (Late-onset) 21-hydroxylase deficiency (21-OHD)

• 11-beta-hydroxylase deficiency

• Overexpression of aromatase

Other hormonal aberrations

• Androgen deficiency (e.g. congenital adrenal hyperplasia)

• Androgen insensitivity

• Extraglandular aromatization of androstenedione (e.g. aromatase excess syndrome (AES), obesity)

Medication

• Anti-androgens (e.g. bicalutamide, flutamide, finasteride, spironolactone)

• Antimicrobials (e.g. antiretrovirals, isoniazid, ketoconazole, metronidazole, penicillamine)

• Antineoplastic and immunomodulators (e.g. alkylating agents, bleomycin, cisplatin, cyclosporine, methotrexate, vincristine)

• Gastrointestinal agents (e.g. cimetidine, metoclopramide, omeprazole, ranitidine)

• Cardiovascular (e.g. amiodarone, amlodipine, angiotensin-converting enzyme inhibitors, calcium channel blockers, digitoxin, fibrates, reserpine, spironolactone, statins)

• Hormones (e.g. androgens, chorionic gonadotropin, estrogens, GnRH agonist, GH)

• Neurologic/psychiatric (e.g. haloperidol, methylphenidate, opioids, risperidone, TCAs)

• Drugs of abuse (e.g. alcohol, amphetamines, heroin, marijuana, methadone)