Gynaecomastia is usually benign but must exclude male breast cancer, testicular malignancy, systemic disease and endocrine emergencies. Act before reassurance.
Male breast cancer is rare but gynaecomastia is a recognised presentation — delay is common because GPs and patients dismiss male breast symptoms. NICE NG12 (updated April 2026) recommends a suspected cancer pathway referral for anyone aged 30 and over with an unexplained breast lump — men included — and for unilateral nipple discharge, retraction or other concerning nipple change at 50 or over. Investigation before referral is not required when breast cancer is suspected.
Testicular tumours (hCG-secreting germ cell tumours, and oestrogen-secreting Leydig or Sertoli cell tumours) and lung carcinomas secrete hCG or oestrogens, causing gynaecomastia before the primary tumour is detected. Missing this means missing a curable cancer.
Hepatic failure, renal failure, hyperthyroidism and pituitary pathology all disrupt sex-hormone binding globulin and peripheral aromatisation — gynaecomastia may be the presenting feature of these serious systemic conditions.
First, establish whether this is true glandular gynaecomastia or adipose tissue (pseudogynaecomastia). Distinguish with the pinch test and focused history.
Many men with apparent gynaecomastia actually have pseudogynaecomastia (lipomastia) — particularly relevant in obesity. The management differs completely: pseudogynaecomastia is addressed through weight management; true gynaecomastia requires cause-finding and targeted treatment.
Duration is critical for prognosis: active-phase gynaecomastia (<6 months) can regress spontaneously or with drug withdrawal. After 12 months, stromal fibrosis means medical treatment is unlikely to work and surgical referral may be the only option if distressing.
Classify by aetiology — drives all subsequent management decisions. Common causes include physiological pubertal or age-related gynaecomastia, medication or anabolic-steroid exposure, obesity/pseudogynaecomastia, hypogonadism, liver or renal disease, and hyperthyroidism. Tumours are uncommon but must be considered when there are red flags or an atypical presentation.
The cause determines management: drug-induced gynaecomastia → stop/switch the drug; hypogonadism → endocrinology/andrology assessment; hyperthyroidism → treatment via the endocrine pathway (NICE NG145); tumour → urgent specialist referral. Getting the aetiology right prevents unnecessary drug treatment with aromatase inhibitors or SERMs.
Klinefelter syndrome is common and frequently undiagnosed into adulthood. Gynaecomastia is a common presenting feature. These patients also have a markedly increased risk of male breast cancer — important cascade of discoveries from one GP consultation.
Full examination is essential to identify systemic causes and exclude malignancy. Always examine genitalia in males with gynaecomastia (with chaperone).
Testicular examination changes management in a significant minority: small testes in a young man with gynaecomastia and infertility strongly suggests Klinefelter syndrome (requires karyotype + endocrinology referral). A painless testicular nodule with gynaecomastia → consider a suspected cancer pathway referral to urology and an urgent direct-access USS (NICE NG12); a painful mass may instead reflect epididymo-orchitis, torsion or trauma.
Signs of liver disease in a man with gynaecomastia should prompt LFTs, clotting, and USS liver — cirrhosis-related gynaecomastia requires hepatology input, not breast treatment. Similarly, thyroid signs should trigger TFTs before any hormonal investigation.
Blood tests are directed by history and examination — there is no universal panel. Many cases need NO tests. Never delay a suspected cancer referral to do tests.
Over-investigation of pubertal gynaecomastia is common and counterproductive — it medicalises a normal physiological process, causes unnecessary anxiety, and rarely changes management. Restrict bloods to adults with unexplained gynaecomastia or when systemic disease is suspected.
The testosterone:LH ratio is the key discriminant: primary hypogonadism (testicular failure) gives high LH + low testosterone; secondary (pituitary/hypothalamic) gives low LH + low testosterone. This distinction determines whether to refer to urology vs endocrinology and whether testosterone replacement is appropriate.
Check β-hCG when onset is rapid, there is a testicular abnormality or a tumour is suspected. A raised or unexpected result needs confirmation and urgent specialist discussion rather than interpretation in isolation. Testicular germ cell tumours are among the commonest cancers in young men and are highly curable if caught early.
Most gynaecomastia is managed in primary care. Refer when investigation reveals systemic cause, malignancy suspected, or treatment is required beyond GP scope.
NICE NG12 (Suspected cancer: recognition and referral, updated April 2026) applies its breast criteria to men as well as women: an unexplained breast lump at 30 or over is a suspected cancer pathway referral, whatever its other features, as is unilateral nipple discharge, retraction or other concerning change at 50 or over. The barrier to a suspected cancer pathway referral in males must be lower than in females given lower baseline suspicion — this is where diagnostic delay occurs.
NHS England data shows median time from symptom to diagnosis for male breast cancer is significantly longer than female breast cancer. GP referral behaviour is the key modifiable factor. When in doubt, refer on the suspected cancer pathway — breast clinics are equipped to discharge rapidly if benign.
Surgical referral for cosmetic subcutaneous mastectomy has a profound impact on quality of life in men with significant gynaecomastia. Document the impact on quality of life, body image, social functioning and expectations, and follow the local ICB surgical-funding policy; a formal psychiatric or psychological assessment is not mandatory in every case.
Treatment is cause-specific. First-line is always cause removal / drug withdrawal. Medical therapy is only appropriate in the active proliferative phase (<6–12 months). GP: cause removal, reassurance, observation and lifestyle. Specialist-initiated only: tamoxifen, testosterone, definitive thyroid treatment and surgery.
Medical therapy for persistent idiopathic/active-phase gynaecomastia — Secondary care initiation only
Next steps: see Breast cancer · Hyperthyroidism
Tamoxifen is an off-label specialist option (licensed in breast cancer treatment), with the best — though limited — evidence in relatively recent, painful gynaecomastia, particularly anti-androgen-associated cases. Aromatase inhibitors have less consistent evidence and are not standard treatment for ordinary idiopathic gynaecomastia.
The critical timing concept: medical treatment only works during active proliferation (ductal epithelial hyperplasia). After fibrosis and hyalinisation (>12 months), no drug reduces breast tissue volume — surgery is the only effective option. This is why accurate assessment of duration is essential at Step 2.
Testosterone replacement in hypogonadal men can paradoxically worsen gynaecomastia initially through peripheral aromatisation of testosterone to oestradiol. Any response to this is specialist-led — adding an aromatase inhibitor is not a routine GP response.
Address obesity, alcohol excess, anabolic-steroid use and recreational-drug use where relevant. Explain that weight loss may improve pseudogynaecomastia and metabolic health, but established glandular tissue may persist.
In obese men, adipose tissue is the primary source of peripheral oestrogen via aromatase activity — a vicious cycle, as oestrogen also promotes further fat deposition. Weight loss may improve pseudogynaecomastia and metabolic health, but established glandular tissue may persist.
Anabolic steroid use is underreported, so ask directly and non-judgementally. Gynaecomastia from AAS is particularly distressing as it occurs in men who are exercising specifically for physique reasons. Post-cycle gynaecomastia is often severe as LH/FSH suppression leads to rebound oestrogen excess.
Psychological impact is often underappreciated by clinicians. Ask about the impact on mood, body image and social functioning, particularly in adolescents.
Gynaecomastia needs structured review: to confirm resolution, detect progression, and maintain vigilance for malignancy. Tailor interval to cause and severity.
Safety-netting is critical because gynaecomastia is a recurring presentation — the GP may be the only clinician reviewing a man whose gynaecomastia is gradually changing character over years. Documenting size in the notes (in cm, not just "improved" or "same") allows objective comparison at follow-up and supports timely escalation.
Men with Klinefelter syndrome have a markedly higher risk of breast cancer than 46,XY males. While absolute risk remains low, this group needs clear long-term monitoring. Many local trusts now have Klinefelter clinics — if available, refer for shared care.
Tamoxifen use carries a small but real VTE risk. If a man is on tamoxifen for gynaecomastia and develops leg swelling or breathlessness, VTE must be excluded. Ensure this is documented in safety-netting advice given to the patient at initiation.