Tumors
Tumor cells may have a secretory potential. Cases where they produce hormones or other proteins that interfere with the testosterone to estrogen ratio, may cause enlarged breasts in men. These include:
- Estrogen or estrogen-like substance producing tumors: The Leydig cell tumors of the testis, and the tumors of adrenal gland cause gynecomastia by releasing estrogen-like substance in the blood. In men, this presents as proliferation of breast tissue.
- Human chorionic gonadotropin-secreting tumors: small cell tumors of the lungs, gastric carcinomas or tumors in the liver may secrete hCG. This hormone drives the testosterone-estrogen ratio out of proportion.