Anorexia nervosa is a potentially life-threatening eating disorder characterized by the inability to maintain a minimally normal weight, a devastating fear of weight gain, relentless dietary habits that prevent weight gain, and a disturbance in the way in which body weight and shape are perceived. A typical case of anorexia nervosa involves a young person (teenager or young adult) who is mildly overweight or of normal weight and who begins a diet and exercise plan to lose weight. As he or she loses weight and receives initial positive reinforcement for this behavior (eg, compliments by peers on his or her appearance), the reward is high and causes an inability to stop this behavior once an ideal weight is achieved. Foremost in the gamut of endocrinologic complications is amenorrhea, although, as previously mentioned, the DSM-5 no longer includes this condition as part of the diagnostic criteria of anorexia nervosa. Osteopenia is a serious complication. Cortical and trabecular bone are affected, and osteopenia persists despite estrogen therapy. Cerebral atrophy and loss of brain volume may be observed in patients with anorexia nervosa. Generalized muscle weakness is the most common neurologic symptom.