The absence of menstruation for four months may be caused by the following reasons: first, polycystic ovary syndrome, which often causes a decrease in menstrual flow or even amenorrhea, and the patient often has the phenomenon of hirsutism, which is also clinically manifested as infertility. Second, caused by the decline of ovarian function, especially in women who are close to perimenopause and have not had a period for four months, it is most likely that the ovarian function has declined and cannot secrete estrogen and progesterone periodically, so they will not have a period. Third, certain factors, such as hyperprolactinemia, can lead to amenorrhea if there is a pituitary tumor, which raises prolactin. Fourth, if there is a history of previous uterine surgery, it may lead to complete adhesions in the uterine cavity and no menstruation.