Gynaecomastia — the benign enlargement of glandular breast tissue in males — is more common than many people realise, affecting adolescent boys, middle-aged men, and older adults alike. Caused by an imbalance between oestrogen and testosterone, it can arise from hormonal changes, certain medications, or underlying health conditions. Although almost always non-cancerous, it can cause significant psychological distress and warrants proper clinical assessment. This article explains how gynaecomastia develops, its common causes, how it is diagnosed, what treatment options are available on the NHS, and what to expect in the long term.

What Is Gynaecomastia and How Does It Develop

Gynaecomastia is the benign enlargement of glandular breast tissue in males, caused by an imbalance between oestrogen and testosterone. It affects newborns, adolescents, and older men, and is distinct from pseudogynaecomastia, which involves excess fatty rather than glandular tissue.

Gynaecomastia is the benign (non-cancerous) enlargement of glandular breast tissue in males. It occurs when the glandular tissue beneath one or both nipples grows beyond its normal size, resulting in a firm or rubbery lump that can sometimes be tender to the touch. It is important to distinguish gynaecomastia from pseudogynaecomastia, which refers to an increase in breast size caused by excess fatty tissue rather than glandular growth. This distinction has practical implications: pseudogynaecomastia is closely linked to excess body weight and may improve with weight management, whereas true gynaecomastia requires a different clinical approach.

The condition develops as a result of an imbalance between the hormones oestrogen and testosterone. Although testosterone is the dominant sex hormone in males, small amounts of oestrogen are also produced. When the ratio shifts — either due to a relative increase in oestrogen or a decrease in testosterone — the breast glandular tissue can be stimulated to grow. This hormonal imbalance can arise from a wide range of physiological, pathological, or pharmacological causes.

Gynaecomastia is common across different life stages. It affects:

• Approximately 40–65% of adolescent boys during puberty, typically resolving within six months to two years in most cases

• Middle-aged and older men, in whom declining testosterone levels play a significant role

• Newborn males, due to transient exposure to maternal oestrogens — this usually resolves within a few weeks to months

While the condition is almost always benign, it can cause considerable psychological distress, particularly in younger males. Understanding its underlying mechanisms is the first step towards appropriate assessment and reassurance.

Sources: NICE CKS: Gynaecomastia; NHS: Gynaecomastia (enlarged male breasts)

Common Causes and Risk Factors in Males

Gynaecomastia is most commonly caused by physiological hormonal changes, medications (including spironolactone, finasteride, and anti-androgens), or pathological conditions such as hypogonadism, liver cirrhosis, or testicular tumours. A thorough medication and lifestyle history is essential in clinical assessment.

Gynaecomastia has a broad range of potential causes, and in many cases more than one contributing factor may be present. Identifying the underlying cause is essential for guiding appropriate management.

Physiological causes account for the majority of cases and include the hormonal fluctuations of puberty, ageing-related testosterone decline, and neonatal oestrogen exposure. These forms typically resolve without intervention.

Medications are among the most frequently identified causes of gynaecomastia in adults. The strength of evidence varies between agents; some associations are well established, while others are based on case reports or limited data. Drugs with a recognised association include:

• Spironolactone (an aldosterone antagonist used in heart failure and hypertension) — well established

• Anti-androgens such as bicalutamide and cyproterone acetate (used in prostate cancer) — well established

• 5-alpha-reductase inhibitors such as finasteride and dutasteride (used for benign prostatic hyperplasia and male-pattern hair loss) — well established

• GnRH analogues (e.g., goserelin, leuprorelin) used in prostate cancer — well established

• Anabolic steroids and exogenous testosterone or oestrogens

• Cimetidine and other H2-receptor antagonists

• Certain antiretrovirals (e.g., efavirenz) — recognised association

• Ketoconazole (systemic use)

• Digoxin and certain chemotherapy agents

• Some antipsychotics (via hyperprolactinaemia), and calcium channel blockers — evidence is weaker for some agents in these classes

Important: Do not stop or change any prescribed medicine without first speaking to your GP or specialist. If you suspect a medicine may be causing gynaecomastia, report it to the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk).

Pathological causes that must be excluded include:

• Hypogonadism (primary or secondary), including Klinefelter syndrome (47,XXY), which is an important underlying cause particularly in men with small testes or fertility concerns

• Hyperthyroidism

• Liver cirrhosis, which impairs oestrogen metabolism

• Chronic kidney disease

• Testicular tumours, which may secrete oestrogen or human chorionic gonadotrophin (hCG)

• Adrenal tumours

Recreational substances — including alcohol and anabolic steroids used for bodybuilding — are also recognised risk factors. The association with cannabis is based on mixed and limited evidence. A thorough medication and lifestyle history is therefore a critical component of any clinical assessment.

Sources: NICE CKS: Gynaecomastia; NHS: Gynaecomastia — causes; BNF monographs (spironolactone, finasteride, dutasteride, bicalutamide, cyproterone); MHRA/EMC SmPCs for relevant medicines

Symptoms, Diagnosis and When to See a GP

Gynaecomastia typically presents as a firm or rubbery disc of tissue beneath the nipple, which may be tender. See a GP promptly if you notice a hard or irregular lump, nipple discharge, skin changes, or rapidly progressive enlargement, as male breast cancer must be excluded.

The most common presenting symptom of gynaecomastia is a palpable, firm or rubbery disc of tissue beneath the nipple-areolar complex, which may be unilateral or bilateral. The area is often mildly tender, particularly in the early or active phase of growth. Some men also notice visible breast enlargement or swelling, which can cause embarrassment or self-consciousness.

It is important to be aware of symptoms that may suggest a more serious underlying condition and warrant prompt medical review. See a GP promptly if you notice:

• A hard, irregular, or fixed lump — particularly if unilateral

• Nipple discharge (especially if bloodstained)

• Skin changes over the breast, such as dimpling or puckering

• Rapidly progressive enlargement

• Associated symptoms such as unexplained weight loss, fatigue, or testicular changes

Although male breast cancer is rare (accounting for less than 1% of all breast cancers in the UK), it must be excluded in any atypical presentation. In line with NICE NG12 (Suspected Cancer: Recognition and Referral), GPs should consider an urgent suspected cancer referral (within two weeks) to a breast clinic for men aged 50 or over with a unilateral, hard subareolar mass with or without nipple discharge or skin changes, and should consider urgent referral for other clinically suspicious features at any age. An urgent urology referral is also warranted where a testicular mass is identified or where hCG is raised, given the possibility of an underlying germ-cell tumour.

Diagnosis is primarily clinical, based on history and physical examination. In typical pubertal gynaecomastia without red flags, examination and follow-up alone are often sufficient, with no further investigation required. Where investigation is indicated, a GP may arrange:

• Blood tests: testosterone, luteinising hormone (LH), follicle-stimulating hormone (FSH), oestradiol, prolactin, thyroid function, liver and renal function, and hCG — targeted according to age, duration, and clinical findings

• Testicular ultrasound if a testicular cause is suspected

• Breast clinic referral for triple assessment (clinical examination, imaging, and where appropriate tissue sampling) if malignancy cannot be excluded; ultrasound is generally the first-line imaging modality in men

NICE CKS guidance supports a structured approach to investigation, with onward referral to endocrinology, urology, or a breast clinic depending on the suspected underlying cause.

Sources: NICE NG12: Suspected cancer — recognition and referral; NICE CKS: Gynaecomastia — assessment and referral; NHS: Breast cancer in men

Treatment Options Available on the NHS

Treatment depends on the underlying cause; watchful waiting is appropriate for physiological cases, while causative medications should be reviewed under medical supervision. Off-label pharmacological options such as tamoxifen require specialist initiation, and NHS surgical funding varies by integrated care board.

The management of gynaecomastia depends on its underlying cause, duration, severity, and the degree of distress it causes the individual. In many cases, particularly in adolescents with physiological gynaecomastia, watchful waiting is the most appropriate initial approach, as the condition frequently resolves spontaneously within six months to two years.

For pseudogynaecomastia, weight management through a balanced diet and regular physical activity is the primary approach, as the breast enlargement is related to excess adipose tissue rather than glandular growth.

Where a causative medication has been identified, the first step is to review — under medical supervision — whether it can be discontinued or substituted. Similarly, addressing underlying conditions such as hypogonadism, hyperthyroidism, or liver disease may lead to gradual improvement in breast tissue.

Simple analgesia (e.g., paracetamol or ibuprofen, if not contraindicated) may help manage breast tenderness during the active phase.

Pharmacological treatment options are not licensed specifically for gynaecomastia in the UK and should only be initiated by a specialist. Their use and availability vary by local integrated care board (ICB) policy. Options that have been used off-label include:

• Tamoxifen (a selective oestrogen receptor modulator, SERM) — this has the best available evidence for reducing breast volume and tenderness, particularly during the early active phase (typically within the first 12 months)

• Raloxifene, another SERM occasionally used off-label — evidence is more limited

• Aromatase inhibitors such as anastrozole — evidence is limited and these are not routinely recommended

None of these medicines hold a UK marketing authorisation for this indication; prescribing is off-label and should be guided by a specialist with reference to current BNF guidance and relevant MHRA/EMC SmPCs.

Surgical treatment — specifically subcutaneous mastectomy or liposuction — may be considered for men with longstanding, fibrotic gynaecomastia that has not responded to other measures and is causing significant psychological or functional impact. NHS funding for surgery varies by ICB and is subject to local clinical commissioning criteria; many ICBs classify it as a procedure of low clinical priority. Patients may need to submit an Individual Funding Request (IFR) demonstrating substantial functional or psychological impairment. The risks of surgery (including scarring, altered sensation, and recurrence) should be discussed fully before any decision is made.

Sources: NICE CKS: Gynaecomastia — management; NHS: Gynaecomastia — treatment; BNF: Tamoxifen, Raloxifene, Anastrozole; MHRA/EMC SmPCs: Tamoxifen, Raloxifene, Anastrozole

Living With Gynaecomastia and Long-Term Outlook

The long-term outlook is generally reassuring, with physiological cases often resolving spontaneously. Gynaecomastia does not typically increase breast cancer risk, though men with Klinefelter syndrome or on long-term oestrogen therapy should remain vigilant and report any new breast symptoms to their GP.

For the majority of men and boys, the long-term outlook for gynaecomastia is reassuring. Physiological gynaecomastia in adolescents typically resolves without treatment, and even in adults, addressing an underlying cause or withdrawing an offending medication can lead to meaningful improvement over time. However, in cases where the condition has been present for more than 12 months, the breast tissue may become increasingly fibrotic, making spontaneous resolution less likely.

The psychological impact of gynaecomastia should not be underestimated. Research consistently shows that the condition can affect body image, self-esteem, and quality of life — particularly in younger males. Feelings of embarrassment, social withdrawal, and avoidance of activities such as swimming or sport are commonly reported. Healthcare professionals should approach these concerns with sensitivity and, where appropriate, refer patients to NHS Talking Therapies (previously IAPT), counselling services, or other local psychological support. Peer support resources may also be helpful.

Practical strategies that some men find helpful include:

• Well-fitted, supportive clothing to minimise the appearance of breast tissue

• Regular physical activity and a balanced diet to support overall body composition and mental wellbeing

• Open discussion with a GP or specialist to ensure all reversible causes have been addressed

Gynaecomastia itself does not generally increase the risk of male breast cancer in the overall population. However, certain underlying conditions — notably Klinefelter syndrome and long-term oestrogen therapy — are associated with a higher background risk, and men in these groups should remain vigilant. All men are encouraged to be breast aware: become familiar with what is normal for you and report any new or changing breast symptoms to your GP promptly. There is no formal breast screening programme for men in the UK.

In summary, gynaecomastia is a common, usually benign condition with a range of identifiable causes and effective management options. Early assessment, accurate diagnosis, and a supportive clinical approach are key to achieving the best possible outcome for those affected.

Sources: NICE CKS: Gynaecomastia — follow-up and patient advice; NHS: Gynaecomastia (enlarged male breasts)

Frequently Asked Questions