Gynecomastia can be caused by physiological reasons and diseases such as breast hyperplasia and breast fibroma. 1. Physiological reasons: mainly common in obese male patients, due to the breast tissue contains fat tissue, when the body type of obesity will lead to the accumulation of fat tissue and thus lead to gynecomastia. When men are in puberty, due to the body of estrogen will appear temporary secretion of abnormalities, can also lead to breast enlargement, when the level of estrogen secretion will be reduced when the breast enlargement will be reduced, will not affect the patient. 2. Breast enlargement: Male breast enlargement can also be called male breast development. Due to the different hormonal environments between men and women, the male breast is not developed, but under the inducement of certain factors, the male breast may also be developed. 3. Breast fibroma: the main symptom of male breast fibroma is commonly found in the upper outer quadrant of the breast, most of them are single, a few of them are multiple, and occasionally they are found on both sides of the breast, the lumps are usually round or oval, the surface of the lumps is smooth, and they are well-moved, and they are not usually accompanied by breast pain. Male breast fibroid development can cause pain and symptoms of breast enlargement. When male patients have enlarged breasts, they should also consider extra-mammary diseases such as chest wall diseases and malignant tumors of the breast, etc. They should go to regular hospitals in time and actively cooperate with the treatment.