Amenorrhea is the absence of a menstrual period not due to pregnancy, breastfeeding, or menopause. Primary amenorrhea is diagnosed when girls have not had their first menstrual period by age 16. It may be caused by an endocrine, genetic, or developmental disorder. Secondary amenorrhea is diagnosed in previously menstruating women who have not had a menstrual period for six months or more. It may be caused by physical or emotional stress, including excessive weight loss, anorexia nervosa, depression, or grief. Many female athletes have secondary amenorrhea due to decreased levels of body fat.