Pain or cramps before or during menstruation. In primary dysmenorrhea, caused by endocrine imbalances, severity varies widely. Irritability, fatigue, backache, or nausea may also occur. Long assumed to be psychosomatic, it is now known to be due to excess prostaglandins, which contract the uterus, causing cramps. Pain relievers that block prostaglandin formation can decrease its severity, which may also be eased after childbearing. Secondary dysmenorrhea is caused by other disorders, including genital obstructions, pelvic inflammation, infection, polyps, or tumours. Treatment is directed toward the underlying disorder.