Decreased testosterone production or action

Reduced testosterone production or action is often associated with increased plasma gonadotrophin levels but not necessarily, with increased plasma oestrogen.

Congenital causes include:

• Klinefelter's syndrome - seen in about 80% of Klinefelter patients, these patients clearly carries an increase risk (10-fold to 20-fold greater than normal) of breast cancer (1)
• testicular feminisation and Reifenstein syndrome
• congenital anorchia - rare - individuals are 46, XY males with normal male phenotype but missing testes. The testes are thought to have been present originally but then to have regressed late in embryonic life
• biochemical defects in testosterone synthesis

Secondary testicular failure may also occur in:

• viral orchitis - the most common cause of testicular failure after puberty; especially, mumps
• trauma - the second most common acquired cause in adults
• castration
• renal failure - gynaecomastia is found in half of the men undergoing haemodialysis for renal failure
• neurological diseases such as myotonic dystrophy - gynaecomastia occuring in three quarters of cases - and spinal cord lesions
• granulomatous disease such as leprosy

Reference:

• (1) Bembo SA, Carlson HE. Gynecomastia: its features, and when and how to treat it. Cleve Clin J Med. 2004;71(6):511-7.