Drug-induced gynecomastia with the benign enlargement of male breast glandular tissue was reported to cause an imbalance between estrogen and androgen action then lead to an increased estrogen to androgen ratio by drugs. Drugs are estimated to cause about 10%~25% of all cases of gynecomastia. Some commonly used drugs, such as spironolactone, ketoconazole, imatinib, bicalutamide, finasteride, cimetidine can cause gynecomastia. Clinical manifestations of drug-induced gynecomastia cause breast pain, tenderness or galactorrhea. Estradiol and estriol increased, while luteinizing hormone (LH), follicle stimulating hormone (FSH), and testosterone decreased in the laboratory tests. In the patients with drug-induced gynecomastia the causative medications should be withdrawn; if gynecomastia persists, the patients can be treated with tamoxifen. Surgery can be performed if treatment with tamoxifen was not effective or the clinical manifestations persist for one year.

Drug toxicity; Gynecomastia; Gonadal hormones