Gynaecomastia is a condition by which males develop breast tissue due to an imbalanced ratio of oestrogen and androgen activity. It is usually a benign disease but breast cancer can develop in about 1% of cases.

Fig. 1 – Hyperplasia of the breast tissue, as seen in as a case of gynaecomastia

It is a common condition with at least a third of men experiencing gynaecomastia in their lifetime and is usually an entirely reversible condition. The condition can cause embarrassment and can be of concern to the patient for a potential underlying malignancy.


Physiological gynaecomastia occurs in newborns, adolescence, and less commonly in the older population, resulting from the presence of maternal oestrogens, delayed testosterone surge relative to oestrogen at puberty, and decreasing testosterone with increasing age respectively.

Pathological gynaecomastia results from changes in the oestrogen:androgen activity ratio and there are a variety of underlying mechanisms:

  • Lack of testosterone
    • Causes include Klinefelter’s syndrome, androgen insensitivity, testicular trauma, or renal disease
  • Increased oestrogen levels
    • Causes include liver disease, hyperthyroidism, obesity, and extreme stress resulting in increased oestrogen levels, alongside many tumour subtypes (e.g. Leydig’s cell tumours)
  • Medication (25% of all cases, either through an increased oestrogen activity or reduced testosterone activity)
    • Common causative agents include digoxin, metronidazole, spironolactone, chemotherapy, goserelin, antipsychotics, and anabolic steroids
  • Idiopathic

Fig. 2 – The enlarged breast tissue, as seen in a case of gynaecomastia

Clinical Features

Gynaecomastia often has an insidious onset. It is essential to ask about co-morbidities, clinical features of potential underlying causes, and any features of potential malignancy.

On examination, gynaecomastia will present as a rubbery or firm mass (typically >2cm diameter) that starts from underneath the nipple and spreads outwards over the breast region. Ensure to check for features of breast malignancy and underlying causes.

Differential Diagnosis

The main differential is psuedogynaecomastia, adipose tissue in the breast region associated with being overweight.

This can usually be tested on examination by pinching to see if there is an obvious disc of breast tissue present however if not palpable then further imaging and / or histology may be required to definitively exclude.


Tests are only necessary if the cause for gynaecomastia is unknown (especially if physiological or iatrogenic). In cases where malignancy is suspected, further investigations need to be performed, such as CXR for lung malignancy or US testes for testicular masses.

In cases where the causes in unknown, liver and renal function (U&Es and LFTs) should be checked initially, before checking the hormone profile if these are normal; the levels of lutenising hormone (LH) and testosterone can indicate different clinical pictures:

  • LH high and testosterone low = testicular failure
  • LH low and testosterone low = increased oestrogen
  • LH high and testosterone high = androgen resistance or gonadotrophin-secreting malignancy


The management ultimately depends on the causative factors and the phase of gynaecomastia.  If there is an underlying cause such as medication then removing this or giving androgens in cases of low testosterone can help.

In most cases, reassurance may be enough for the patient; Tamoxifen can also be used in cases to help alleviate symptoms, especially tenderness. In patients with later stages of fibrosis, surgery may be the only option if medical treatments have failed.

Key Points

  • Pathological gynaecomastia occurs from changes in the oestrogen:androgen activity ratio
  • It will present as a rubbery or firm mass, starting from underneath the nipple and spreading outwards over the breast region
  • Tests are only necessary if the cause for gynaecomastia is unknown


Question 1 / 3
Which of the following medication is known to cause gynaecomastia?


Question 2 / 3
Which of the following genetic disorders is most associated with gynaecomastia?


Question 3 / 3
A patient presenting with gynaecomastia secondary to testicular failure would present with which of the following blood panels?


Further Reading

Thiruchelvam P at al., The BMJ

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