If a woman’s menstruation is less than 20 days, she has a shortened menstrual cycle. There are many reasons for this condition, and it is most common in clinical practice in the following cases: first, endocrine disorders, such as luteinizing insufficiency, hyperthyroidism, hypovarianism, etc. Patients need to check sex hormone six, anti-Mullerian duct antibodies, and thyroid function to make a clear diagnosis; second, benign neoplastic lesions Second, benign neoplastic lesions, such as adenomyosis and uterine fibroids. Fibroids and adenomyosis can lead to an enlarged uterine body and poor contraction of the muscular layer, so the patient will have frequent menstruation and heavy menstruation, and other abnormalities; Fourth, blood system diseases, such as patients with thrombocytopenia, or other hematological tumor diseases.