In recent years, male breast development has been on the rise. Many male patients will touch a lump in the chest, enlarged breasts with some symptoms such as pain and itchiness, and worry if they have breast cancer. So what kind of disease is it? First of all, gynecomastia is a benign disease with very little cancer. The causes are: 1. 2.Changes in the response of breast tissue to hormones: In some cases, the level of sex hormones in the blood circulation is normal, but the response of tissue to hormones has changed, androgen receptors are not sensitive to testosterone, resulting in an imbalance in the ratio of estrogen/androgen in the breast, and the role of estrogen is relatively enhanced, resulting in breast enlargement. 3, sex hormone metabolism disorder: the local aromatase enzyme in the breast increases, resulting in enhanced estrogen aromatization of androgens. Therefore, this is the basis for the use of aromatase inhibitors for gynecomastia. 4.Functional or organic changes in the hypothalamus-pituitary gland and the endocrine axis under its control. 5, medical factors: estradiol transdermal therapy for prostate cancer; treatment of hypertensive spironolactone, etc. may lead to gynecomastia. 6, obesity factors: survey found that the number of male breast development in obese people is much higher than the general population. 7, the cause is unknown: about half or more than half of the male breast development can not find a clear cause, a variety of hormone measurements are normal, the clinical diagnosis is usually idiopathic male breast development, but the latest research that it may be related to environmental pollution. Some of the environmental pollutants are estrogen-like compounds.