GPAtlas🧭 When to suspect
Gynaecomastia is the benign proliferation of true glandular breast tissue in males, driven by a shift in the oestrogen-to-testosterone ratio (relative oestrogen excess or androgen deficiency).
It is felt as a firm, rubbery, concentric disc of tissue, classically ≥ 2 cm beneath the nipple–areolar complex, and may be unilateral or bilateral. It is distinct from pseudogynaecomastia – soft, fatty chest enlargement seen in obesity, with no glandular disc.
It is common:
• Around a third of adult men are affected at some point, with peak prevalence between 50 and 69 years.
• Over half of adolescent boys develop transient pubertal gynaecomastia.
• There are three physiological peaks – neonatal, pubertal and senescent (older age).
In practice:
• Confirm it is true gynaecomastia (not pseudogynaecomastia or a discrete breast lump)
• Identify a reversible cause, above all a drug
• Exclude the rare but serious mimics – male breast cancer and a testicular or hCG-secreting tumour – some of which need an urgent suspected cancer pathway referral (previously the two-week wait)
| Category | Typical causes |
|---|---|
| Physiological | • Neonatal (maternal oestrogen) • Pubertal (resolves in > 90% within ~3 years) • Senescent (falling testosterone with age) |
| Drug-induced | Spironolactone, digoxin, finasteride/dutasteride, anti-androgens (e.g. bicalutamide), cimetidine, proton pump inhibitors (PPIs), antipsychotics, anabolic steroids, cannabis, alcohol, opioids |
| Pathological | Hypogonadism (including Klinefelter's syndrome), testicular or hCG-secreting tumours, chronic liver disease, hyperthyroidism, chronic kidney disease |
| Idiopathic | No cause found after assessment – around a quarter of adult cases |
Source: NICE NG12 · Association of Breast Surgery
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