Most patients who have a change in menstruation can be evaluated and treated on the basis of a brief history, a physical examination, and a few laboratory tests. Because menstrual dysfunction can cause worry and inconvenience, patients should be promptly treated. Pregnancy must be excluded as a cause of amenorrhea in the initial evaluation. Other possible causes that must be ruled out include hypothalamic or pituitary tumors and severe thyroid disease. Amenorrhea should be treated to avoid possible complications such as osteoporosis, cardiovascular disease, and uterine or endometrial cancer. Treatment methods depend on whether the lack of menstruation is caused by an excessive estrogen level or estrogen deficiency.