A girl, just half a year old, started to develop larger breasts and darker nipples and areolas at 2 months after birth, and her leucorrhoea increased in the last 2 months and she seemed to start menstruating. She went to the pediatrician’s office and had her endocrinology checked, and the female hormones in her blood had reached adult levels. Ultrasound revealed that the girl’s uterus and ovaries had developed and were almost at adult level. After many consultations and treatments, we finally checked the brain MRI and found a small mass of one centimeter in diameter in the brain called hypothalamus, which was identified as hypothalamic malformation tumor. After careful discussion with the child’s parents, we decided to operate and remove the hypothalamic malformation tumor. The girl recovered well after surgery without sequelae, and the above-mentioned symptoms of precocious puberty gradually subsided after surgery. Blood and ultrasound were repeated at the age of 1 year, and female hormone levels and uterus and ovaries were found to have returned to k-child status. In a boy, at the age of 1 year, his parents noticed paroxysmal unexplained smiling expressions for a few seconds each time, several times a day, and did not pay much attention to them. Later, however, the boy was found to have a small beard, to speak with an adult voice, to have a thickened penis, and to have an erection sometimes. The parents panicked and went to the hospital to check the endocrine system and found that androgens in the blood had reached adult levels. The MRI revealed a hypothalamic malformation, which had to be treated surgically. ………… What is hypothalamic malformation tumor? First, a brief introduction to the hypothalamus. The hypothalamus is located at the base of the brain, in the upper part of the pituitary gland, and is one of the most important vital centers, in charge of consciousness, wake-sleep cycle, thermoregulation and functional activities of water, salt and endocrine in the whole body. The nerve centers for drinking and eating are located in it. Hypothalamic malformation is a rare congenital developmental abnormality. Although it is called a tumor, it is not a tumor, but a mass of nerve cells that should not be present in this part of the hypothalamus due to abnormal displacement of nerve cells during fetal life. Hypothalamic malformations are not composed of tumor cells, but of nerve cells. These nerve cells can discharge and produce substances with endocrine functions like normal nerve cells. This leads to a range of neuroendocrine disorders. The main manifestations of hypothalamic malformation tumors are, as in the previous two cases, precocious puberty and dementia epileptica. In this case, the paroxysmal laughter produced by the child is a manifestation of epilepsy. Of course, other types of seizures can be combined. Magnetic resonance is the primary means of confirming the diagnosis. There is no obvious effective drug treatment for premature sexual development and demented laughter epilepsy caused by hypothalamic malformation tumors, and surgical removal of hypothalamic malformation tumors is the main effective treatment. There are various surgical approaches, depending on the specific growth pattern of the lesion, and some complex cases may require combined surgical approaches, etc.