Drugs causing breast enlargement in a male

Drug-induced gynecomastia is common and may account for 20% to 25% of cases (1) .These may be categorised into:

• oestrogens and oestrogen like drugs, for example –
  • diethylstiboestrol;
  • exposure to partners using oestrogen containing vaginal creams;
  • cosmetics containing oestrogens
  • foods contaminated with oestrogens for example, from oestrogen or diethylstilboestrol injected cows
  • phyotoestrogens
  • digitalis administration, although the pathophysiology is poorly understood
    
    
• drugs which enhance oestrogen formation for example –
  • gonadotrophins such as hCG
  • following withdrawal of clomiphene which may result in increased secretion of LH and consequently, of testicular oestradiol
    
    
• drugs which inhibit
  • testosterone synthesis - ketoconazole, metronidazole, spironolactone, chemotherapy (cytotoxic drugs) (2)
  • testosterone action
    • androgen receptor blockers - bicalutamide
    • 5 α reductase inhibitors - finasteride, dutasteride
    • H2 blockers and proton pump inhibitors
    • marijuana (2)
      
      
• drugs whose mechanism of action is unknown (it is thought that many may act by altering liver function)
  • tricyclic antidepressants-may increase the prolactin levels.(2)
  • angiotensin converting enzyme inhibitors. (2)
  • heroin
  • amiodarone
  • busulfan
  • methyldopa
  • captopril
  • growth hormone
  • highly active antiretroviral therapy
  • calcium channel antagonists - long term use of verapimil
  • isoniazid (2)
    
    
• others situations which can cause or lead to gynaecomastia :
  • increasingly body builders taking anabolic steroids may present with gynaecomastia
  • healing balms, scented soaps, skin lotions, shampoos and styling gels containing lavender oil and tea tree oil

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.
• (2) Niewoehner CB, Schorer AE. Gynaecomastia and breast cancer in men. BMJ. 2008 Mar 29;336(7646):709-13.