Normally, male mammary glands do not develop. When there is an imbalance in the sex hormone ratio in the body and the estrogen/androgen ratio rises, then the male mammary glands develop like the female mammary glands. And one of its possible main causes is pituitary tumor. The hypothalamus and pituitary gland are the control centers of human endocrine secretion, and the hypothalamic-pituitary-gonadal axis is a branch that controls the secretion of human sex hormones. Once a tumor grows in the pituitary gland, it may lead to abnormal changes in the hypothalamic-pituitary-gonadal axis, resulting in endocrine disorders. For men, there may be too much estrogen and lactogen and less androgen secretion, which will lead to an imbalance in the ratio of sex hormones in the body and an increase in the estrogen/androgen ratio; breast development also appears, and it may also manifest as no beard, no laryngeal nodes, loss of libido, impotence, overflow of breast, and in severe cases, genital atrophy. In severe cases, genital atrophy, low sperm count, low activity, and infertility can be manifested. In patients with gynecomastia, the symptoms of reduced beard and body hair should not be taken for granted as a result of obesity, but may be related to intracranial tumors, and a pituitary hormone test and head MRI are needed to clarify the diagnosis. If the diagnosis of lactating pituitary tumor is confirmed, early treatment can be done by oral bromocriptine. If oral bromocriptine is not effective and the tumor does not grow under control, surgical treatment should be considered. Today, we treated a patient with a lactating pituitary tumor. The patient was 38 years old, male, and his main symptom was breast development for 7 years, during which the patient had surgery to remove the hyperplastic breast tissue. The patient was admitted to our hospital with pituitary tumor, and today, under general anesthesia, she was given a transnasal pituitary tumor excision; I would like to express my views on what I saw during the operation: 1, most of the lactogenic pituitary adenomas can control the symptoms and tumor growth by taking bromocriptine orally; 2, if the symptoms and tumor growth cannot be controlled within 1 year after taking the medication regularly under the guidance of the doctor, it is recommended to have surgery as soon as possible; in this case, we saw that the tumor center was soft and fragmented, but the periphery of the tumor was tough and tightly adhered. It took a lot of effort to remove the tumor completely, which may be related to long-term medication and ineffective medication.