If menstruation is always early, the menstrual cycle will be shortened, often due to the following reasons: The first is due to endocrine disorders, such as luteal insufficiency, which leads to early menstruation and shortened cycles. The second is due to submucosal fibroids, which grow into the uterine cavity and increase the size of the endometrium, thus affecting the contraction of the uterus and leading to a shorter menstrual cycle, longer periods, irregular vaginal bleeding or increased menstrual flow, which can lead to anemia in severe cases. Thirdly, inflammation of the endometrium, endometrial polyps, or pelvic tumors may cause early menstruation.