🚨 Male breast masses in older men must be considered malignant until proven otherwise → urgent referral to a breast clinic according to NICE suspected cancer referral guidance. Gynaecomastia is the benign proliferation of glandular breast tissue in males and may be physiological, drug-induced, or secondary to systemic disease.

📖 Overview

Gynaecomastia: benign enlargement of male glandular breast tissue (distinct from fat deposition in obesity).
Common causes include physiological hormonal imbalance, medications, endocrine disease, or systemic illness.
Important to distinguish from male breast cancer, which is typically unilateral, firm, and eccentric from the nipple.

🩺 Clinical Features

Breast swelling, usually tender and rubbery, centred beneath the areola.
Often bilateral and symmetrical in physiological or drug-induced cases.
Look for endocrine features:
- Hypogonadism – testicular atrophy, infertility, low libido.
- Pituitary disease – galactorrhoea, headaches, visual disturbance.
- Systemic disease – jaundice (liver disease), weight loss (thyrotoxicosis), oedema (renal disease).

📊 Common Causes

Cause	Clinical Clues	Key Tests	Management
👦 Pubertal	Bilateral, adolescence, self-limiting	Clinical assessment	Reassurance
💊 Drug-induced	Spironolactone, cimetidine, anti-androgens	Medication review	Stop or substitute drug
🧬 Hypogonadism	Testicular atrophy, infertility	↓ Testosterone, ↑ LH/FSH	Treat cause ± testosterone therapy
🍺 Liver disease	Signs of chronic liver disease	LFTs, imaging	Manage liver disease
🔥 Hyperthyroidism	Weight loss, tremor, tachycardia	TSH suppressed, ↑ T4	Treat thyrotoxicosis
🎱 Testicular tumour	Testicular mass	Scrotal ultrasound, tumour markers	Urgent urology referral

💊 Drug Causes of Gynaecomastia

🧠 Key idea: gynaecomastia occurs when there is increased oestrogen effect relative to androgen effect at breast tissue. Drugs may cause this by reducing testosterone, blocking androgen receptors, increasing prolactin, increasing oestrogen, or impairing liver metabolism of hormones.

Drug / Class	Examples	Mechanism / Notes
🧪 Anti-androgens	Finasteride, dutasteride, bicalutamide, flutamide, cyproterone	Reduce androgen action or testosterone conversion. Common in prostate disease treatment.
💧 Spironolactone	Spironolactone	Classic cause. Anti-androgen effect and altered testosterone/oestrogen balance. Eplerenone is less likely.
❤️ Cardiovascular drugs	Digoxin, amiodarone, calcium-channel blockers, ACE inhibitors	Digoxin has oestrogen-like activity. Others are less common but reported.
🔥 Acid-suppressing drugs	Cimetidine, omeprazole, other PPIs	Cimetidine is classic due to anti-androgen effects. PPIs are less common but reported.
🧠 Antipsychotics	Risperidone, amisulpride, haloperidol, phenothiazines	Increase prolactin by dopamine blockade → hypogonadism and breast tissue stimulation.
🧠 Antidepressants	SSRIs, TCAs, venlafaxine	Uncommon; may be linked to prolactin changes or altered sexual hormone balance.
⚡ Antiepileptics	Phenytoin, carbamazepine, valproate	May alter hepatic metabolism of sex hormones. Not a common cause, but recognised.
🦠 Antiretrovirals	Efavirenz, protease inhibitors	Efavirenz is a recognised cause; may alter oestrogen/androgen signalling.
🧫 Antifungals	Ketoconazole	Inhibits steroid synthesis → reduced testosterone production.
💉 Hormones / anabolic agents	Oestrogens, anabolic steroids, testosterone misuse	Anabolic steroids can aromatise to oestrogen and suppress endogenous testosterone.
🧪 Chemotherapy / cancer drugs	Alkylating agents, imatinib, methotrexate	May cause testicular dysfunction or alter hormone balance.
🧴 Recreational drugs	Cannabis, alcohol, heroin, amphetamines	Associations reported. Alcohol also contributes through liver disease and hypogonadism.
💊 Other reported drugs	Isoniazid, metronidazole, theophylline, diazepam	Less common; consider if timing fits and other causes have been excluded.

🎓 Exam Tips

💧 Spironolactone is the classic exam drug cause.
🔥 Cimetidine is another classic cause due to anti-androgen activity.
🧠 Risperidone and amisulpride cause hyperprolactinaemia and can lead to gynaecomastia.
🧪 Finasteride, dutasteride and bicalutamide are important prostate-related causes.
🍺 Always ask about alcohol, anabolic steroids and cannabis.

🧠 Memory aid: “SACRED” causes gynaecomastia:
💧 Spironolactone
🧪 Anti-androgens / anabolic steroids
🔥 Cimetidine
🧠 Risperidone
🦠 Efavirenz
❤️ Digoxin

🧪 Investigations

Blood tests: testosterone, LH, FSH, prolactin, oestradiol, hCG.
Thyroid function tests.
Liver function tests and renal profile.
Scrotal ultrasound if testicular tumour suspected.
Breast ultrasound ± mammography if malignancy suspected.
Biopsy if the mass is unilateral, firm, fixed, or associated with nipple discharge or skin changes.

⚕️ Management

Treat the underlying cause.
Stop or substitute causative medications.
Hormonal therapy if hypogonadism is present.
Reassurance for physiological pubertal gynaecomastia.
Surgical management (subcutaneous mastectomy) for persistent symptomatic cases.
Urgent referral for suspected malignancy.

💡 Exam Tip: Tender bilateral breast enlargement in adolescents → usually physiological. A firm unilateral breast lump in an older man → consider breast cancer until proven otherwise.

📚 References (NICE)

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Gynaecomastia ✅