Can steroids cause gynaecomastia? Yes — steroid use, particularly anabolic-androgenic steroids (AAS), is a well-recognised cause of abnormal breast tissue growth in males. This occurs primarily through aromatisation, a process by which androgens are converted into oestrogen, disrupting the hormonal balance in the male body. Prescribed corticosteroids have also been occasionally linked to breast changes, though less commonly. This article explains the mechanisms involved, which steroids carry the highest risk, how to recognise the signs, and what steps to take — including NHS treatment and management options — if you notice breast tissue changes.

How Steroids Can Cause Gynaecomastia

Anabolic-androgenic steroids cause gynaecomastia by aromatising into oestrogen, raising oestrogen levels relative to testosterone and stimulating glandular breast tissue growth in males.

Gynaecomastia — the benign enlargement of glandular breast tissue in males — is a recognised complication of steroid use, both prescribed and non-prescribed. Understanding the underlying mechanism helps explain why this side effect occurs and who may be most vulnerable.

Steroids, particularly anabolic-androgenic steroids (AAS), can disrupt the hormonal balance between oestrogen and testosterone in the male body. When exogenous (externally introduced) androgens are introduced, the body responds by converting a proportion of these androgens into oestrogen through a process called aromatisation, mediated by the enzyme aromatase. Elevated oestrogen levels relative to androgens stimulate the growth of breast glandular tissue, leading to gynaecomastia.

Additionally, when a person stops using anabolic steroids, the body's natural testosterone production — which has been suppressed during the cycle — takes time to recover. During this window, oestrogen levels may temporarily dominate, further increasing the risk. This hormonal imbalance, whether during or after steroid use, is the primary driver of steroid-induced gynaecomastia.

Prescribed corticosteroids (such as prednisolone) have occasionally been associated with gynaecomastia, though this is considered uncommon and the evidence is less well established than for AAS. The proposed mechanisms include indirect effects on the hypothalamic-pituitary-gonadal axis and metabolic changes. Patients taking long-term prescribed corticosteroids who notice breast changes should discuss these with their GP or specialist, rather than assuming a causal link.

If you suspect a medicine is causing a side effect, you can report it via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk or through the Yellow Card app.

Which Types of Steroids Carry the Highest Risk

Highly aromatisable AAS — including testosterone, nandrolone, and methandrostenolone (Dianabol) — carry the greatest risk; stanozolol and oxandrolone are lower risk but not without hormonal consequences.

Not all steroids carry the same risk of causing gynaecomastia. The likelihood depends largely on the specific compound, its tendency to aromatise, and the dose and duration of use.

Anabolic-androgenic steroids (AAS) most commonly associated with gynaecomastia include:

• Testosterone (in all its esterified forms, e.g., testosterone enanthate, cypionate) — highly aromatisable

• Nandrolone (Deca-Durabolin) — aromatises at a lower rate but may contribute to gynaecomastia via progesterone receptor activity

• Methandrostenolone (Dianabol) — a strongly aromatising oral steroid widely misused in bodybuilding

In contrast, steroids such as stanozolol and oxandrolone have low aromatisation potential and are considered lower risk, though they are not entirely without hormonal consequences. It should be noted that many AAS — including boldenone — are not licensed for human use in the UK and are obtained illicitly; their use carries significant health risks beyond gynaecomastia.

Among prescribed corticosteroids, an association with gynaecomastia has been reported, particularly with long-term use at higher doses, though this is considered uncommon. Patients should not stop prescribed corticosteroids without medical advice.

It is also important to recognise that polypharmacy — the concurrent use of multiple substances — can amplify risk. Many individuals misusing AAS also use other compounds, including human chorionic gonadotrophin (hCG), which directly stimulates testicular oestrogen production and is a well-recognised cause of gynaecomastia. Other medicines with established links to gynaecomastia include anti-androgens, spironolactone, and ketoconazole. The higher the dose and the longer the duration of steroid exposure, the greater the cumulative hormonal disruption and associated risk.

For further information on drug-induced gynaecomastia, refer to the NICE CKS: Gynaecomastia topic and the BNF monographs for individual medicines.

Recognising the Signs and Symptoms of Gynaecomastia

Gynaecomastia typically presents as a firm, rubbery lump beneath the nipple, with possible tenderness or asymmetrical breast swelling; red flag features such as a hard lump or nipple discharge require urgent medical review.

Early recognition of gynaecomastia is important, both to distinguish it from other conditions and to seek timely medical advice. The condition can affect one or both breasts and may present differently depending on its stage and cause.

Common signs and symptoms include:

• A firm, rubbery or disc-like lump of tissue felt directly beneath the nipple or areola

• Breast tenderness or sensitivity, particularly when pressure is applied

• Swelling or enlargement of one or both breasts, which may be asymmetrical

• Nipple sensitivity or discharge (less common, but warrants prompt medical review)

It is essential to distinguish true gynaecomastia (involving glandular tissue) from pseudogynecomastia, which refers to fatty tissue accumulation in the chest area without glandular involvement — a distinction that has implications for both diagnosis and treatment. True gynaecomastia typically presents as a palpable, firm mass beneath the nipple, whereas pseudogynecomastia tends to feel softer and more diffuse.

Duration matters: gynaecomastia detected early (within the first six to twelve months) is more likely to respond to medical treatment. Long-standing gynaecomastia (typically beyond twelve months) tends to become fibrotic and is less amenable to pharmacological management, making early presentation important.

While steroid-induced gynaecomastia is generally benign, any new breast lump or change in breast tissue should be assessed by a healthcare professional to rule out other causes, including male breast cancer, which, although rare, accounts for approximately 1% of all breast cancer diagnoses in the UK (Cancer Research UK). Red flag symptoms — such as a hard or irregular lump, skin changes, nipple inversion, or bloody discharge — require urgent medical evaluation and should not be attributed to steroid use without proper clinical assessment.

In line with NICE NG12 (Suspected cancer: recognition and referral), an unexplained breast lump in a male aged 30 or over, or suspicious nipple changes, should prompt urgent referral via the suspected cancer pathway. A testicular examination should also be considered, as testicular tumours can cause gynaecomastia through raised beta-human chorionic gonadotrophin (beta-hCG); any testicular abnormality warrants further assessment.

What to Do If You Notice Breast Tissue Changes

Contact your GP promptly and disclose all steroid use; your GP will take a history, examine you, arrange hormone blood tests, and refer urgently if red flag features are present.

If you notice any changes in your breast tissue — whether you are currently using steroids, have used them in the past, or are taking prescribed corticosteroids — it is important to seek medical advice promptly rather than waiting to see if the changes resolve on their own.

Your first step should be to contact your GP. Be open and honest about any steroid use, including non-prescribed anabolic steroids. Whilst there may be concerns about disclosure, your GP is bound by patient confidentiality and needs an accurate medical history to provide safe and appropriate care. Withholding information about substance use can delay diagnosis and lead to inappropriate management.

During your consultation, your GP will likely:

• Take a detailed history, including medication and substance use

• Perform a clinical breast examination and, where indicated, a testicular examination

• Request blood tests to assess hormone levels, including 9am total testosterone, oestradiol, LH, FSH, prolactin, sex hormone-binding globulin (SHBG), beta-hCG, thyroid function, and liver and renal function (LFTs and U&Es)

• Consider referral for breast ultrasound if the diagnosis is uncertain or if there are any concerning features

• Arrange testicular ultrasound if the testicular examination is abnormal or if beta-hCG is raised

If red flag features are present (see above), your GP should refer you urgently via the suspected cancer pathway in line with NICE NG12.

If you are using non-prescribed anabolic steroids, your GP may also refer you to a drug and alcohol service or a specialist harm reduction service, many of which offer non-judgemental support. In the UK, organisations such as FRANK (talktofrank.com), local needle exchange programmes, and NHS image and performance enhancing drug (IPED) services can provide additional guidance.

If you are taking prescribed corticosteroids and develop breast changes, do not stop your medication abruptly without medical advice, as this can be dangerous. Instead, contact your prescribing clinician to discuss your concerns and explore whether dose adjustment or an alternative treatment is appropriate.

Treatment and Management Options Available on the NHS

Stopping steroid use is the primary treatment step; pharmacological options such as tamoxifen are off-label, and NHS surgery is restricted to cases meeting Integrated Care Board clinical thresholds.

The management of steroid-induced gynaecomastia depends on several factors, including the underlying cause, the duration of the condition, the degree of breast tissue development, and the impact on the individual's quality of life. NICE CKS: Gynaecomastia and NHS clinical pathways support a stepwise approach to treatment.

Addressing the underlying cause is the first and most important step. For those using non-prescribed anabolic steroids, cessation of use is strongly recommended. In many cases — particularly when gynaecomastia is detected early — stopping steroid use and allowing the body's hormonal balance to normalise may lead to partial or complete resolution of breast tissue changes over several months. Medical treatment is most effective within the first six to twelve months of onset; long-standing, fibrotic gynaecomastia is less likely to respond.

Pharmacological options may be considered in some cases, particularly where gynaecomastia is persistent or causing significant distress:

• Tamoxifen (a selective oestrogen receptor modulator, or SERM) is sometimes used off-label to reduce breast tissue in males. There is limited evidence supporting its use in gynaecomastia management, and it should only be used under the supervision of a clinician familiar with its risks and interactions (see BNF and EMC SmPC for tamoxifen). It is not a routine NHS treatment for gynaecomastia caused by non-prescribed steroid misuse.

• Aromatase inhibitors (such as anastrozole) are generally not recommended for gynaecomastia outside specialist settings; evidence for their use is limited and they carry significant risks. They should not be sourced or used without medical supervision.

• Do not attempt to obtain SERMs or aromatase inhibitors online or without a prescription. Unsupervised use carries serious health risks and these medicines are not licensed for this indication.

Surgical intervention — specifically subcutaneous mastectomy or liposuction — may be considered for established, fibrotic gynaecomastia that has not responded to conservative management and is causing significant psychological distress. NHS funding for surgical treatment of gynaecomastia is subject to Integrated Care Board (ICB) policies and NHS England Evidence-Based Interventions (EBI) criteria, which restrict access to surgery to cases meeting specific clinical thresholds. Patients should discuss eligibility with their GP or specialist.

Regardless of the treatment pathway, psychological support should not be overlooked. Body image concerns and the pressures that may have led to steroid use are important considerations. Referral to NHS Talking Therapies (formerly IAPT) may be beneficial alongside physical treatment; ask your GP for a referral or self-refer via the NHS website.

If you believe a medicine has caused or contributed to gynaecomastia, please report this via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk.

Frequently Asked Questions