The function of the pineal gland is not well understood, and it is generally believed that the human pineal gland synthesizes and secretes a variety of bioglycans and peptides, mainly to regulate the secretion of nerves and the function of the reproductive system. And this regulation has a strong biological rhythm and is related to the intensity of light. Pineal cells secrete melatonin and 5-hydroxytryptamine alternately, with a clear circadian rhythm, secreting 5-hydroxytryptamine during the day and melatonin during the night. Melatonin may inhibit the synthesis and secretion of gonadotropins and their releasing hormones, which has an inhibitory effect on reproduction. In addition, in recent years, it has been found that pineal cells also secrete 8-sperm oxytocin, luteinizing hormone-releasing hormone and antigonadotropic factor, the significance of which is still unclear.