Prepubescent unilateral gynecomastia secondary to excessive soy consumption

We present a case of an unusual cause of prepubertal gynecomastia.

Enlargement of breast tissue in males, or gynecomastia, is a rare condition in prepubescent boys. We describe an 8-year-old male who developed unilateral gynecomastia secondary to marked dietary soy consumption. While the majority of cases are idiopathic, soy products, particularly those consumed by our patient, can contain high levels of phytoestrogens, which have been documented in limited case studies to contribute to abnormal development of breast tissue in adolescent and adult males. To our knowledge, this is the first documented case of gynecomastia occurring in a prepubescent patient resulting from excessive intake of dietary soy. Importantly, we also report a complete resolution of gynecomastia upon exclusion of dietary products containing significant amounts of soy.

While soybeans and soy-derived products can be an important source of nutrition for some, those with abnormal sensitivity to phytoestrogens may benefit from limiting dietary soy consumption to avoid potential adverse effects, including gynecomastia.