The time of gynecomastia, including: neonatal period, puberty and old age. 1, neonatal period, the incidence of 60%-90%, manifested as breast nodule enlargement, which is due to maternal or placental estrogen, into the fetal circulation, the role of the breast tissue, caused by the general 1-3 weeks can be subsided. 2, puberty, puberty, males will have a transitory breast enlargement, the incidence of which is about 30%-60%. It usually starts at the age of 10-12 and reaches its peak at the age of 13-14, and lasts for a short period of time, from a few months to 2 years. Most of the pubertal male breast development can return to normal state within 1 year, which is mainly related to the imbalance of male estrogen and male hormone secretion.3. Geriatric gynecomastia, which is common at the age of 50-80 years old, is mostly accompanied by different degrees of testicular function decline, and the metabolism of estrogen and male hormone has changed, including the decline of serum total testosterone level, plasma free testosterone level has been reduced. The plasma free testosterone level has been reduced. In addition, the increase of fat content in the body tissues of the elderly, so that the aromatase action of the peripheral tissues is enhanced, which can cause an increase in the ratio of estrogen to androgen in the plasma and breast tissues, so that the breast tissues appear to be hyperplasia.