Reasoning GP · Algorithm · 1-page summary
Gynaecomastia
For: male breast enlargement at any age — neonatal, pubertal, adult, age-related or drug-induced — in primary care. Not for: breast symptoms in women (use the breast pages). There is no dedicated NICE guideline; follow local breast, urology and endocrine pathways.
Core rule: review the drug chart and feel the testes. A hard, eccentric breast mass or a testicular tumour must not be missed, and a suspected cancer referral is never delayed for blood tests or imaging.
0Stop — emergency now — before reassurance
- Acute severe testicular pain (especially with nausea, high-riding testis or abnormal lie) → emergency torsion assessment 999 / A&E
- Acute liver failure or severe systemic illness (e.g. confusion), acute adrenal crisis, pituitary emergency, severe hypercalcaemia with confusion → 999 / A&E
- Chest pain or sudden breathlessness → emergency assessment whatever the gynaecomastia; consider PE if on tamoxifen or with VTE risk factors 999
1Triage — true gynaecomastia? which pattern?
| Pattern | Action |
|---|---|
| Pseudo | Soft fat, no glandular disc on pinch test → weight management; no tests |
| Neonatal, pubertal | Typical, no red flags → reassure and observe; no tests |
| Drug-induced | Clear link, no atypical features → causality review; no routine tests |
| Adult, unclear | Recent, marked, progressive or atypical → selective tests (block 3) |
Duration: <6 months active, may regress · >12 months likely fibrosis.
2Screen — one row is enough
- Unexplained breast lump aged ≥30, with or without pain (men included) → Suspected cancer pathway (NG12). No tests or imaging first.
- Aged ≥50: unilateral nipple discharge, retraction or other concerning nipple change → Suspected cancer pathway. Any age: hard, fixed or eccentric mass, skin tethering, ulceration, Paget's, spontaneous bloody discharge → Urgent specialist discussion
- Painless testicular mass or change in shape/texture → consider suspected cancer pathway to urology + direct-access USS Urgent. Do not wait for tumour markers.
- Weight loss, drenching sweats, lymphadenopathy → Urgent bloods + CT (lymphoma, lung cancer). Raised β-hCG → Urgent specialist, not 999.
- Jaundice or signs of liver decompensation → Same-day medical
- Galactorrhoea → prolactin; markedly raised, headache or visual field loss; or absent puberty + anosmia → Urgent endocrine
3Assess — history and examination first
☐ Pinch test: subareolar disc vs fat ☐ Breasts, nipples, axillae ☐ Testes, with chaperone (small firm → Klinefelter) ☐ Liver, thyroid signs, BMI ☐ All drugs incl. OTC, anabolic steroids, recreational, herbal
Tests only if cause unclear, recent, marked, progressive or atypical: morning testosterone (repeat if low), LH, FSH, U&E, LFT, TSH; β-hCG if rapid onset or testicular concern; prolactin, oestradiol if indicated. Not routine: mammogram, scrotal USS.
4Classify — only if the screen is negative
- Physiological — neonatal, pubertal (10–17), older adult (>50). Tender, concentric disc.
- Drug-induced — spironolactone, anti-androgens, oestrogens, anabolic steroids, finasteride/dutasteride, cimetidine, ketoconazole, digoxin → causality review.
- Hypogonadism — high LH/FSH + low testosterone = primary (karyotype); low LH/FSH + low testosterone = secondary → endocrinology.
- Systemic — liver, renal disease, hyperthyroidism → treat the cause.
- Tumour — low LH/FSH + high oestradiol, or raised β-hCG → urgent specialist discussion.
- Uncertain / idiopathic — only after selective assessment; review at ~3 months with size in cm.
5Treat today — cause first
- Drug-induced: stop or switch the culprit only where safe, with the prescriber; allow 3–6 months to regress.
- Pubertal: reassure — most resolve within 18–24 months; review 6-monthly.
- Obesity, alcohol, anabolic steroids: NHS Tier 2 weight management; ≤14 units/week over 3+ days; non-judgemental harm reduction. Semaglutide only in a specialist service (TA875).
- Hyperthyroidism: refer endocrinology (NG145). Specialist-only: tamoxifen, testosterone, surgery. Do not stop spironolactone, digoxin, amiodarone or anti-androgens without the prescriber.
6Refer routinely
- Urgent endocrinology (2–4 weeks): confirmed hypogonadism, Klinefelter, low LH + low testosterone, clearly raised oestradiol.
- Routine endocrinology: recent, painful, persistent → specialist tamoxifen; young man with senescent pattern.
- Surgery: longstanding fibrotic, significant pain or distress, persistent deformity; true gynaecomastia only; local ICB funding policy.
- Psychological distress → NHS Talking Therapies.
7Never reassure by
- Male sex — men get breast cancer; a lump at ≥30 goes on the pathway.
- Bilateral, tender tissue — the testes still need examining.
- A known causative drug, when the mass is hard, eccentric or fixed.
- Normal or pending bloods — never delay a cancer referral for tests.
- Normal tumour markers — they do not exclude a testicular tumour.
- "Improved" or "same" without the disc size in cm.
8Safety-net — say it, then document it
999 / A&E “Sudden severe pain in a testicle, chest pain or sudden breathlessness — call 999 or go to A&E now.” Same day: “The lump turns hard, irregular or fixed, new nipple discharge, fast growth, weight loss or night sweats, a new painless lump in a testicle, or yellow skin or eyes — contact us today.”
Review: pubertal at 6 months; drug stopped at 3 months; idiopathic at ~3 months. On tamoxifen: VTE and visual symptoms.
✓Safe to manage in primary care only if — all five, documented
No block 0–2 row applies
True vs pseudo confirmed by pinch test
Testes examined; full drug history taken
Cause or uncertainty stated; size in cm; review date set
Safety-net given and documented
Summary of the full Reasoning GP gynaecomastia algorithm, which holds the detail, drug lists, interpretation and evidence. Sources: NICE NG12 (updated April 2026), NG145, NG131, TA875; Society for Endocrinology / ACB 2023; BSSM 2022. Clinical reference — follow local breast, urology and endocrine pathways and check doses: NICE/SPC, BNF.