Nipple discharge is mostly related to the high level of prolactin secreted by pituitary gland, so nipple discharge is a "barometer" of prolactin level in vivo. There are two main cases of prolactin increase: one is that the pituitary gland itself has a tumor, and the other is that the nerve center dysfunction makes prolactin inhibitory factor produce too little or stop secreting. For example, mental patients who commonly use chlorpromazine, hypertensive patients who take reserpine, patients who often take motilium stomach disease, insomnia patients who often take diazepam, oral contraceptives and anti-tuberculosis drugs. Their blood prolactin levels increased significantly, leading to nipple discharge. In addition, hypothyroidism, hemophilia, thrombocytopenic purpura, renal insufficiency, bronchial cancer, diabetes, breast trauma, breast inflammation and so on. It can also cause nipple discharge.