Overview
Gynaecomastia describes an increase in male breast volume which most commonly occurs during times of significant hormonal changes, such as adolescence and old age. it occurs due to an increased oestrogen:androgen ratio The majority of cases of gynaecomastia are idiopathic.
Causes
Physiological causes
- Newborns – due to maternal oestrogen. Resolves in a few weeks.
- Adolescence – generally resolves within 1-2 years
- Increasing age – due to testosterone decline
Pathological causes
- Increased oestrogen levels/activity:
- Obesity – due to increased aromatase activity (converts testosterone into oestrogen)
- Anabolic steroid use/excess androgen replacement – extra testosterone is converted into oestrogen
- Testicular cancers (e.g. seminoma) – secrete hCG which stimulates oestrogen production
- Decreased testosterone levels/activity:
- Gonadal disorders (e.g. Kallmann’s syndrome)
- Hyperprolactinaemia (e.g. pituitary tumours)
- Testicular failure (e.g. infection such as mumps, haemochromatosis, Klinefelter’s syndrome)
- Drug causes:
- Drugs stimulating oestrogen receptors:
- Digoxin
- Phenytoin
- Drugs reducing testosterone levels/activity:
- Spironolactone – most common
- Gonadotropin-releasing hormone agonists (GnRH)
- Androgen receptor blockers (e.g. bicalutamide)
- 5-alpha reductase inhibitors (e.g. finasteride)
- Cimetidine
- Ketoconazole
- Metronidazole
