20 years old 3 months without menstruation, may be caused by physiological reasons, such as early pregnancy, mental stress, etc., but also may be caused by pathological reasons, such as polycystic ovary syndrome, hypothyroidism, it is recommended to seek medical attention in a timely manner to clarify the causes and give appropriate treatment and treatment. I. Physiological causes: 1. Early pregnancy: If you have had sex recently, you should first observe whether there is a possibility of pregnancy through early pregnancy test paper. If the test paper results suggest pregnancy, you should go to the hospital for pregnancy checkup in time; 2. High mental stress: In modern society, work pressure, life pressure and mental stress are relatively high, which can easily trigger endocrine disorders in 20-year-old women, with amenorrhea or delayed menstruation. Such patients often also have insomnia, hair loss, dreamy and other symptoms performance. It is recommended to do proper exercise every day, communicate with friends, and take a short trip to improve the state of excessive stress; 3, weight: low weight or obesity can affect the normal hormone secretion of the body, resulting in menopause, which needs to be regulated under the guidance of a professional nutritionist, or through traditional Chinese medicine to regulate; 4, drug effects: long-term oral contraceptives or injections of methylhydroxyprogesterone contraceptive injection, or taking Anti-psychotic drugs, chemotherapy drugs for malignant tumors, antidepressants, antihypertensive drugs, anti-allergic drugs, etc., may trigger the phenomenon of menopause, generally 3-6 months after stopping the drug, menstruation can mostly recover naturally. Pathological causes: 1. Polycystic ovary syndrome: the cause is unknown, but it can occur in young women, causing delayed menstruation, low menstrual flow, or even amenorrhea. Patients are often also accompanied by obesity, acne, hair loss and other manifestations. If the above-mentioned symptoms occur at the same time, they can be treated by short-acting compound oral contraceptives, detrofloxacin, micronized progesterone and other drugs after they are clearly identified by ultrasound and hormonal examination. 2. Endometrial damage: Due to previous abortion or curettage, the endometrium is damaged, resulting in uterine cavity adhesions, which affects the normal proliferation and shedding of the endometrium, causing the patient not to have menstruation for three months. Adhesive tissues can be separated under direct hysteroscopy, followed by high doses of estrogen and placement of supports in the uterine cavity to keep it dilated; 3. Hypothyroidism: often caused by thyroiditis, thyroid surgery, iodine deficiency, etc., can lead to endocrine disorders in women, resulting in women not getting their periods for three months. If the absence of menstruation is accompanied by coldness, weakness, unresponsiveness, facial edema, and low sweating, it is recommended to go to the hospital for a thyroid function test. The treatment is mainly by giving levothyroxine to normalize the endocrine system in the patient’s body so that menstruation can be restored to normal; 4. Other diseases: In addition to the above, it can also be caused by various conditions such as hypothalamic tumor, Sheen syndrome, pituitary tumor, head trauma, adrenal cortical tumor, etc. So if you have not had your period for three months, you should go to the hospital for a systematic examination in time to protect your health.