Noncancerous enlargement of one or both breasts in males

  • Most common in newborn babies and adolescents
  • Alcohol abuse and being overweight are risk factors in adults
  • Genetics is not a significant factor

All males produce small amounts of the female sex hormone oestrogen. If too much oestrogen is produced, breast enlargement, called gynaecomastia, occurs. One or both breasts may be affected. The condition is common in newborn boys and affects 1 in 2 male adolescents. It is usually temporary in both of these age groups. Older men can also be affected.


An excess of the female sex hormone oestrogen in the blood may cause one or both male breasts to enlarge, as seen here.

What are the causes?

Gynaecomastia in the newborn occurs when the fetus has been exposed to the mother’s oestrogen within the uterus. Increased levels of oestrogen, resulting in breast enlargement, are also common during puberty. In adults, alcohol abuse and being overweight are the most common causes of gynaecomastia.

Drugs that affect levels of female sex hormones, such as spironolactone (see Diuretic drugs) and corticosteroids, may lead to enlargement of the breasts. Some drugs for prostate cancer (see Drugs for prostate disorders) may have the same effect.

What are the symptoms?

The symptoms of gynaecomastia may include the following:

  • Tender and swollen breast or breasts.

  • Firm or rubbery button of tissue that can be felt underneath the nipple.

  • Discharge from the nipple.

One breast may enlarge more than the other. The symptoms listed here should always be investigated so that breast cancer can be excluded.

What might be done?

Newborn boys do not need treatment, and gynaecomastia usually disappears within a few weeks. In most adolescents, the condition disappears in less than 18 months without any treatment. In older men, the doctor will ask about lifestyle factors and carry out a physical examination. He or she may arrange for tests to measure hormone levels and to look for evidence of breast cancer. The treatment and outlook depend on the underlying cause, but, if gynaecomastia persists, the excess tissue may be removed surgically.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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