Decreased menstrual flow, which is clinically defined as less than 20 ml, can be diagnosed as menorrhagia, often due to the following reasons: First, hyperandrogenemia can lead to decreased menstrual flow. Secondly, hyperprolactinemia can also lead to decreased menstrual flow. Third, due to tuberculosis in the pelvis, the destruction of the endometrium can also cause a decrease in menstrual flow. Fourthly, in the clinical situation is the case of polycystic ovary syndrome, the menstrual flow will also be reduced. Fifth, because of damage to the endometrium, such as a history of abortion, or a history of curettage, or a history of diagnostic curettage, causing damage to the endometrium and incomplete adhesions in the uterine cavity, the menstrual flow will also be reduced clinically. It is recommended to take blood test for sex hormone six, check thyroid function, combine with clinical history and ultrasound, and then give appropriate treatment.