Gynecomastia (GYN), is a clinical condition in which male breast tissue develops abnormally and the connective tissue of the breast proliferates abnormally. It usually presents as painless, progressive enlargement of one or both breasts or as a painful lump in the subareolar area, sometimes with a milk-like discharge. Gynecomastia is the most common breast disease in men and can occur at any age. 1. Etiology Gynecomastia is mainly related to sex hormones. Possible pathogenic mechanisms include increased estrogen, lack of androgen, and increased ratio of estrogen to androgen. Recent domestic and foreign studies have also proved that local factors such as defective estrogen receptor function and increased sensitivity of breast tissue to estrogen also play a role in its occurrence. Gynecomastia can be classified as physiologic, pathologic, or idiopathic according to its etiology. Physiological gynecomastia mostly occurs during puberty under the age of l8 years, when sex hormone secretion is high and anterior pituitary gonadotropins stimulate the production of testosterone and estrogen, resulting in a decrease in the ratio of androgens to estrogens in the serum and a transient increase in male breast development. Pathological gynecomastia is mostly caused by side effects of medications, but can also be caused by diseases such as tumors. Obesity factors obesity can induce breast development and the two are positively correlated. Bad eating behavior (such as eating high-calorie food, snacking, often drinking sugary drinks, etc.) and bad living habits (such as moving less and sleeping, watching TV, often playing video games, etc.) can easily lead to obesity. Therefore, the role of lifestyle habits and behaviors in the occurrence of GYN is receiving increasing attention. Unknown cause About 5O% or more of GYN can not find a clear cause, a variety of hormone measurements are normal, the clinical diagnosis of this is usually idiopathic GYN. 2, treatment Longer course, hyperplastic glands have been replaced by fibrous tissue and glass-like changes, even after the removal of the cause can not completely recede (2 years without receding), the need to give surgical treatment. The surgical treatment is minimally invasive areolar small incision gland excision + chest fat aspiration (most gynecomastia is accompanied by chest fat accumulation), which is less invasive and quicker to recover, and the surgery is done on an outpatient basis and you can go home afterwards. The post-operative appearance is good and surgical marks are difficult to detect. Insist on wearing an elastic undershirt for 2-3 months after surgery for better results.