There are many reasons why a 17-year-old may not have a period for five months and should be treated promptly by a doctor. Common ones include menstrual disorders, polycystic ovary syndrome, and other endocrine disorders. If pregnancy occurs at this age due to unprotected sex, it can also occur for several months without a period. Common causes and treatments 1, menstrual disorders: excessive dieting, staying up late, stress, etc. can cause symptoms such as prolonged periods and reduced menstrual flow, accompanied by abdominal pain, dizziness, etc. Hormone and ultrasound examinations are feasible to confirm the diagnosis, such as ultrasound examination of endometrial thickening, progesterone treatment is available; 2, polycystic ovary syndrome: often have scanty menstruation with symptoms such as hirsutism and acne, serum hormone level measurement and ultrasound examination should be done to confirm the diagnosis. Ultrasound examination should be done to confirm the diagnosis, and short-acting compound oral contraceptives and progesterone can be applied to regulate the menstrual cycle to promote normal ovulation; 3, other endocrine diseases: such as abnormal thyroid function, hyperprolactinemia, etc., the corresponding hormone examination is feasible to clarify; 4, pregnancy: do not exclude seventeen-year-old women have sex and not contraceptive, this situation may be related to pregnancy or endometrial adhesion after abortion, should The diagnosis should be confirmed by blood HCG and ultrasonography. Precautions adolescent women should avoid emotional excitement caused by work or study stress, learn to self-regulate, through effective ways such as listening to music to relieve stress; avoid excessive consumption of fried, smoked food, to prevent excessive obesity caused by abnormal ovulation, but also not excessive dieting to lose weight, will affect the normal secretion of hormones in the body; pay attention to warmth, avoid cold and cold; ensure sufficient sleep, try not to stay up late. Keep warm and avoid cold.