Functional uterine bleeding, referred to as “gonorrhea”, refers to irregular vaginal bleeding in women and is a common gynecological disorder among women of childbearing age. It can cause various gynecological diseases and infertility, and frequent and prolonged bleeding can cause anemia in women. So, what is the cause of functional uterine bleeding? 1, systemic factors: This factor mainly includes adverse mental trauma, stress, malnutrition, endocrine and metabolic disorders, such as iron deficiency, anemia, remittent anemia, blood disorders and bleeding disorders, diabetes, thyroid and adrenal disorders. 2. Dysfunction: This etiology mainly includes disorders of reproductive hormone release rhythm, feedback dysfunction, ovulation and luteal dysfunction. 3, medical factors: common steroidal contraceptives, intrauterine devices interfere with the normal hypothalamic-pituitary-gonadal axis function. Certain drugs for systemic diseases, especially the psychiatric and neurological system can affect normal menstrual function through the neuroendocrine mechanism. 4, the uterus and endometrial factors: including small spiral arteries, microcirculatory vascular bed structure and function abnormalities, endothelial steroid receptor and lysosomal dysfunction, local coagulation mechanism abnormalities, and prostaglandin secretion dysregulation.