Objective: To document a case of gynecomastia related to ingestion of soy products and review the literature.

Methods: We present the clinical course of a man with gynecomastia in relation to ingestion of 2 different soy products and review related literature.

Results: A 60-year-old man was referred to the endocrinology clinic for evaluation of bilateral gynecomastia of 6 months' duration. He reported erectile dysfunction and decreased libido. On further review of systems, he reported no changes in testicular size, no history of testicular trauma, no sexually transmitted diseases, no headaches, no visual changes, and no change in muscular mass or strength. Initial laboratory assessment showed estrone and estradiol concentrations to be 4-fold increased above the upper limit of the reference range. Subsequent findings from testicular ultrasonography; computed tomography of the chest, abdomen, and pelvis; and positron emission tomography were normal. Because of the normal findings from the imaging evaluation, the patient was interviewed again, and he described a daily intake of 3 quarts of soy milk. After he discontinued drinking soy milk, his breast tenderness resolved and his estradiol concentration slowly returned to normal.

Conclusions: This is a very unusual case of gynecomastia related to ingestion of soy products. Health care providers should thoroughly review patients' dietary habits to possibly reveal the etiology of medical conditions.