The mechanisms underlying anorexia and its physiological consequences are well understood thanks to scientific studies, but research into its causes—including psychological ones—remains incomplete. The endocrinology team at Saint-Étienne University Hospital presents here the main current clinical, somatic, and psychological aspects of anorexia nervosa. These practitioners conclude that it occurs "in patients with a controlling, perfectionist, and persevering personality," leading to weight loss that is resistant to the effects of appetite-regulating hormones. Prompt multidisciplinary care is recommended.