Gynaecomastia is the enlargement of glandular tissue of the breast and should be distinguished from an increase in adipose tissue. It is usually bilateral, but may be strikingly asymmetrical, or unilateral. It results from an increase in the effective oestrogen: androgen ratio within the mammary tissue.
Physiological gynaecomastia can occur at the extremes of life, but is most common during puberty, when it usually lasts for only a few months, although may persist into adulthood.
The index of suspicion and therefore the need for endocrine investigation of gynaecomastia will depend on the age of the subject and findings on detailed history and physical examination. Pathological gynaecomastia is likely when sudden enlargement occurs unrelated to puberty particularly in young boys or middle aged men. The most common identifiable cause is drug therapy, but there is no obvious aetiology in up to 50% of cases.
Initial steps should include a detailed drug history. A positive drug history cannot exclude a breast cancer which should always be considered, especially in the elderly. Endocrine investigations should be considered if gynaecomastia is persistent or progressive.
The underlying cause in the majority of cases will be an imbalance in the functional ratio between androgens and oestrogens. Altered breast tissue response may be considered if all other identifiable causes are excluded.
Ismail AAA, Barth JH. The endocrinology of gynaecomastia. Ann Clin Biochem 2001;38:596-607.