<prompt> Not a cause of gynecomastia :INHspironolactoneDigitalisPyrazinamide  <response>: Gynecomastia refers to enlargement of the male breast. It is caused by excess estrogen action and is usually the result of an increased estrogenandrogen ratio. Drugs can cause gynecomastia by acting directly as estrogenic substances e.g., oral contraceptives,isoniazid INH,phytoestrogens, digitalis, inhibiting androgen synthesis e.g., ketoconazole, or action e.g., spironolactone. Ref :Bhasin S., Jameson J.L. 2012. Chapter 346. Disorders of the Testes and Male Reproductive System. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo Eds, Harrisons Principles of Internal Medicine, 18e. 