The absence of menstruation is often due to the following reasons: 1. In women of childbearing age, if menopause occurs without contraception, it is often caused by pregnancy. 2. The absence of menstruation due to endocrine disorders, such as prolonged late nights, irregular life, excessive smoking and drinking, or sudden environmental changes or cold stimulation, may lead to menopause. 3. Menorrhagia can be caused by diseases such as polycystic ovary syndrome, endometrial tuberculosis, or pelvic tumors. 4. Menorrhagia caused by endometrial damage, such as repeated abortions, resulting in endometrial damage and adhesions in the uterine cavity, causing amenorrhea in clinical practice. 5. Menorrhagia caused by premature ovarian failure.