Gynaecomastia refers to the enlargement of the glandular breast tissue in males. Male breast enlargement is relatively common, particularly in adolescents and older men (aged over 50 years). It may also be present in newborns due to circulating maternal hormones, resolving as the maternal hormones are cleared.



Gynaecomastia is generally caused by a hormonal imbalance between oestrogen and androgens (e.g., testosterone), with higher oestrogen and lower androgen levels. Raised oestrogen stimulates breast development, whilst androgens have an inhibitory effect on breast development.

Prolactin is a hormone that also stimulates glandular breast tissue development (as well as breast milk production). Therefore, raised prolactin (hyperprolactinaemia) can cause gynaecomastia.  It is worth remembering that dopamine has an inhibitory effect on prolactin. Dopamine antagonists (e.g., antipsychotic medications) block dopamine production, which can allow prolactin levels to rise and cause gynaecomastia and galactorrhea (breast milk production). 

Gynaecomastia is idiopathic in many cases, meaning no cause is found.

Gynaecomastia may be physiological in adolescents, where there can be proportionally higher oestrogen levels around puberty. This resolves after a few years, as the hormone levels balance.

Gynaecomastia can be caused by conditions that increase oestrogen:

  • Obesity (aromatase is an enzyme found in adipose tissue that converts androgens to oestrogen)
  • Testicular cancer (oestrogen secretion from a Leydig cell tumour)
  • Liver cirrhosis and liver failure
  • Hyperthyroidism
  • Human chorionic gonadotrophin (hCG) secreting tumour, notably small cell lung cancer


TOM TIP: It is worth remembering the link between gynaecomastia and Leydig cell testicular tumours. About 2% of patients presenting with gynaecomastia have a testicular tumour. An examination question might describe a patient presenting with gynaecomastia and ask what additional examination should be performed. The answer will be a testicular examination. Also, examine for signs of liver failure and hyperthyroidism.


Gynaecomastia can be caused by conditions that reduce testosterone:

  • Testosterone deficiency in older age
  • Hypothalamus or pituitary conditions that reduce LH and FSH levels (e.g., tumours, radiotherapy or surgery)
  • Klinefelter syndrome (XXY sex chromosomes)
  • Orchitis (inflammation of the testicles, e.g., infection with mumps)
  • Testicular damage (e.g., secondary to trauma or torsion)


There is a long list of medications and drugs that can cause gynaecomastia:

  • Anabolic steroids (raise oestrogen levels)
  • Antipsychotics (increase prolactin levels)
  • Digoxin (stimulates oestrogen receptors)
  • Spironolactone (inhibits testosterone production and blocks testosterone receptors)
  • Gonadotrophin-releasing hormone (GnRH) agonists (e.g., goserelin used to treat prostate cancer)
  • Opiates (e.g., illicit heroin use)
  • Marijuana
  • Alcohol


TOM TIP: It is worth remembering spironolactone as a cause for gynaecomastia, as this seems to come up in exams. It is also worth remembering to ask about anabolic steroid use, as this is the most common cause I have seen in young men in clinical practice. A large proportion cases of gynaecomastia will be idiopathic.



It is important to distinguish between gynaecomastia and breast enlargement due to obesity (pseudogynaecomastia). On palpation, there will be firm tissue behind the areolas in gynaecomastia, representing growth of the gland and duct tissue. This is different to simple adipose (fat) tissue, which is soft and more evenly distributed.

The next step is to try and establish the cause.


The key points to cover in the history are:

  • Age of onset, duration and change over time
  • Associated sexual dysfunction (indicating low testosterone)
  • Any palpable breast lumps or skin changes (exclude breast cancer)
  • Associated symptoms that may indicate the cause (e.g., testicular lumps or symptoms of hyperthyroidism)
  • Prescription medication (e.g., antipsychotics, spironolactone or GnRH agonists)
  • Use of anabolic steroids, illicit drugs or alcohol


The key points to cover in the examination are:

  • True gynaecomastia versus simple adipose tissue
  • Unilateral or bilateral
  • Any palpable lumps, skin changes or lymphadenopathy (exclude breast cancer)
  • Body mass index (BMI)
  • Testicular examination (e.g., lumps, atrophy or absence)
  • Signs of testosterone deficiency (e.g., reduced body and pubic hair)
  • Signs of liver disease (e.g., jaundice, hepatomegaly, spider naevi and ascites)
  • Signs of hyperthyroidism (e.g., sweating, tachycardia and weight loss)



Investigations will be determined by history and examination findings. Simple gynaecomastia in an otherwise healthy adolescent may be managed with watchful waiting. Unexplained rapid-onset gynaecomastia in a 30 year old male with no apparent cause may require in-depth investigations. 


Blood tests:

  • Renal profile (U&Es)
  • Liver function tests (LFTs)
  • Thyroid function tests (TFTs)
  • Testosterone
  • Sex hormone-binding globulin (SHBG)
  • Oestrogen
  • Prolactin (hyperprolactinaemia)
  • Luteinising hormone (LH) and follicle-stimulating hormone (FSH)
  • Alpha-fetoprotein and beta-hCG (testicular cancer)
  • Genetic karyotyping (if Klinefelter’s syndrome is suspected)



  • Breast ultrasound (may help assess the extent of gynaecomastia)
  • Mammogram (if cancer is suspected)
  • Biopsy (if cancer is suspected)
  • Testicular ultrasound (if cancer is suspected)
  • Chest x-ray (if lung cancer is suspected)



Management depends on the underlying cause. Gynaecomastia almost always resolves with time in adolescents. Stopping a causative drug (e.g., anabolic steroids or spironolactone) will usually resolve the symptoms. Patients may be referred to the specialist breast clinic where the cause is unclear or cancer is suspected.

Treatment options in problematic cases (e.g., pain or psychological distress) include:

  • Tamoxifen (a selective oestrogen receptor modulator that reduces the effect of oestrogen on the breast tissue)
  • Surgery


Last updated June 2021