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, and over half of adolescent boys develop transient pubertal gynaecomastia. There are three physiological peaks – neonatal, pubertal and senescent (older age).
The primary-care task is threefold: confirm it is true gynaecomastia (not pseudogynaecomastia or a discrete breast lump); identify a reversible cause, above all a drug; and exclude the rare but serious mimics – male breast cancer and a testicular or hCG-secreting tumour – some of which need an urgent two-week-wait (2WW) suspected-cancer referral.
| 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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