There are primary and secondary amenorrhea. Those who have reached the age of 16 and have not yet had their first menstruation are referred to as primary amenorrhea; those who have stopped menstruating for more than three months after the onset of menstruation are referred to as secondary amenorrhea. The occurrence of amenorrhea accounts for a large proportion of reproductive-related disorders in adolescence. The common causes are as follows: 1. Uterine causes: Also called uterine amenorrhea. It is caused by problems with the uterus, such as congenital absence of the uterus, uterine dysplasia, etc. Such conditions are manifested as primary amenorrhea. The clinical diagnosis is easily confirmed by ultrasound and sex hormone measurements, but one thing should be noted: in cases of congenital absence of the uterus, further chromosomal and genetic measurements are needed to determine whether the condition is hermaphroditic or not, especially to determine the presence of cryptorchidism, so that early surgery can be performed to prevent the occurrence of cancer. In addition, some lesions involving the endometrium during childhood can also lead to primary amenorrhea, such as endometrial tuberculosis, endometrial schistosomiasis, endometrial septicemia, etc. 2. Ovarian causes: Also known as ovarian amenorrhea. Normal menstruation occurs because the reproductive endocrine axis (hypothalamus-pituitary-ovary) secretes normal levels of reproductive hormones that act on the endometrium, causing it to change, then shed, bleed and form. The ovaries secrete hormones such as estrogen, progesterone and androgen, and imbalance in the levels and ratios of these hormones can also lead to menstrual disorders. The common clinical manifestations of this disease include obesity, hirsutism, acne, scanty menstruation and even amenorrhea. With the increasing incidence of the disease in recent years, scholars have to consider whether it is related to food and environmental pollution. Therefore, we need to instruct adolescents suffering from this disease to eat less fried and additive-containing foods and to consume green and natural foods as much as possible. If necessary, a combination of Chinese and Western medicine is given. 3, pituitary causes: called pituitary amenorrhea. The pituitary gland is located underneath the brain and is small in size, but commands the endocrine organs of the body. When the pituitary gland function changes, ovarian function decreases. The common pituitary lesions are tumors and hypopituitarism. The diagnosis can be helped by CT of the cranial pterygoid saddle and sex hormone measurement, and both have corresponding clinical treatment measures. The central nervous system includes the brain and hypothalamus, which command the activities of the pituitary gland and indirectly control ovarian function. When the central nervous system is stimulated, it causes changes in ovarian function and leads to amenorrhea. Sudden amenorrhea can occur when there is excessive mental stress, excessive academic pressure, or a change in geographic environment. For children with a heavy study load at the moment, active physical exercise can make this condition adjustable. 5, other causes: This category includes a wide range of causes, such as: systemic diseases, endocrine diseases, psychotropic drugs, immunosuppressive drugs, rapid elimination of C, etc. For this particular stage of adolescence, excessive weight loss is a more common reason, some statistics show that: below 10% of the standard weight, the menstrual cycle can change, and when below 15% of the standard weight. Then amenorrhea can occur, especially anorexia due to excessive dieting, is a relatively difficult clinical treatment of a disease, and even affect the future reproductive function, so we must guide them, reasonable weight control. It can be seen that amenorrhea is a symptom of many diseases. When amenorrhea occurs, the cause should first be investigated and then treated so as not to delay the detection of important diseases.