What are the causes of gynaecomastia?

Gynaecomastia

It is found in the following conditions: 

Physiological: gynaecomastia typically occurs at 3 distinct periods of life

• Neonatal: due to crossing of maternal and placental estrogens into newborn’s circulation
• Puberty:  In whom estradiol concentrations reach adult levels before testosterone
• Adult life: Occurs in 50-80 years of age due to decreasing testosterone concentrations

Drug-induced

• Spironolactone
• Cimetidine
• Digoxin
• Finasteride
• Anti-androgens (cyproterone acetate, spironolactone)
• Some exogenous anabolic steroids (diethylstilbestrol)
• Cannabis

Hypogonadism

Androgen resistance syndromes

Oestrogen excess

• Liver failure (impaired steroid metabolism)
• An oestrogen-secreting tumour (e.g. of testis)
• A human chorionic gonadotropin-secreting tumour (e.g. of testis or lung)

Syndromes with androgen deficiency: Kallman's, Klinefelter's

Testicular failure: e.g. mumps

Testicular cancer:  e.g. seminoma (secreting hCG), teratoma

Source:

• Davidsons Principles and Practice of Medicine 23th edition; 657
• Kumar & Clark’s Clinical Medicine 9^th edition: 1218