Gynecomastia By Irvin H Hirsch, MD, Sidney Kimmel Medical College of Thomas Jefferson University Reviewed / Revised Feb 2023 View Patient Education Pathophysiology Etiology Evaluation Treatment Key Points Topic Resources Gynecomastia Some Causes of Gynecomastia Common Drug Causes of Gynecomasti... Interpretation of Some Findings... Gynecomastia is hypertrophy of breast glandular tissue in males.