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 (~400 UK cases/year) but gynaecomastia is a recognised presentation — delay is common because GPs and patients dismiss male breast symptoms. NICE NG12 mandates 2WW referral for any unexplained lump in males.
Testicular germ cell tumours (especially Leydig cell and Sertoli cell) 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.
Up to 65% of 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. Drugs and physiological causes account for ~75% of cases.
The cause determines management: drug-induced gynaecomastia → stop/switch the drug; hypogonadism → testosterone replacement; hyperthyroidism → carbimazole; tumour → urgent surgery. Getting the aetiology right prevents unnecessary drug treatment with aromatase inhibitors or SERMs.
Klinefelter syndrome (1:600 males) is frequently undiagnosed into adulthood. Gynaecomastia is the most common presenting feature. These patients also have 20–50× 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 nodule in a testis with gynaecomastia = germ cell tumour until proven otherwise.
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.
Investigate systematically. Many cases (pubertal, drug-induced) need NO tests. Match investigation intensity to clinical suspicion.
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.
β-hCG must be checked in all adult males with gynaecomastia — a serum level of even 5 IU/L should trigger urgent testicular USS and urology referral. Germ cell tumours are the most common cancer in men aged 20–40 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) is explicit: any unexplained lump in the breast of a male patient should trigger a 2WW referral, regardless of clinical features. The barrier to 2WW 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 2WW — 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. In the NHS, this requires careful documentation of psychological distress and failed medical treatment — start that paper trail early if surgery is being considered.
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). Specialist-initiated only for SERMs and aromatase inhibitors.
Medical therapy for persistent idiopathic/active-phase gynaecomastia — Secondary care initiation only
Tamoxifen has the strongest evidence base for medical treatment of gynaecomastia, with response rates of 60–80% in active-phase disease. It is used off-label (licensed in breast cancer treatment). Aromatase inhibitors have less evidence but are useful when tamoxifen is not tolerated.
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. Endocrinology will often co-prescribe tamoxifen short-term when initiating TRT to mitigate this effect.
Lifestyle modification is first-line treatment in many cases — not an afterthought. Address these at every consultation alongside medical management.
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 is genuinely disease-modifying: in morbidly obese men who achieve >10% weight loss, gynaecomastia regresses in a substantial proportion without any other intervention.
Anabolic steroid use is dramatically underreported — surveys suggest 1 in 20 gym-attending men have used AAS. 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. Studies show adolescent males with gynaecomastia have rates of depression and social anxiety comparable to those with visible skin conditions like acne. Proactive mental health assessment should be routine.
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 20–50× the risk of breast cancer compared to 46,XY males. While absolute risk remains low (~3% lifetime), 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.