Long hair on the chest may be caused by physiological factors, which are related to heredity; it may also be caused by pathological factors, such as polycystic ovary syndrome, Cushing’s syndrome and other common diseases. 1. Physiological factors: If both parents have hairy chests, the phenomenon of hairy chests in children is higher than in the general population, which is a normal physiological phenomenon. 2. Pathologic factors: common diseases such as polycystic ovary syndrome, Cushing’s syndrome and so on. (1) Polycystic Ovary Syndrome: Polycystic Ovary Syndrome is a reproductive endocrine metabolic disease, and genetic, environmental and other factors related to the patient’s body androgen levels rise, which will lead to chest hair growth. (2) Cushing’s syndrome: Cushing’s syndrome is mainly caused by abnormal regulation of the hypothalamus-pituitary-adrenal axis, the body’s glucocorticoid secretion is higher, and one of the side effects of glucocorticoid is hirsutism, which results in chest hair growth. There are more reasons for chest hair growth, after excluding physiological factors, it is recommended to go to the regular hospital to clarify the cause of the disease and avoid excessive anxiety.