Anorexia nervosa (AN) is a chronic childhood psychiatric illness that involves a reduction in caloric intake, loss of weight and amenorrhea, either primary or secondary. The diagnostic criteria for AN have been established by the American Psychiatric Association. The prevalence of this disease amongst adolescents and young adults is between 0.5 and 1% and the incidence of new cases per year is approximately 5-10/100,000 between 15 and 19 years of age.A number of endocrine and metabolic disturbances have been described in patients with AN including amenorrhea-oligomenorrhea, delayed puberty, hypothyroidism, hypercortisolism, IGF-I deficiency, electrolyte abnormalities, hypoglycemia and hypophosphatemia, among others. In addition to prolonged amenorrhea, osteopenia and osteoporosis are the most frequent complications leading to clinically relevant fractures and increased fracture risk throughout life. Patients exhibit an alteration in the hypothalamic-pituitary-gonadal axis, which is responsible for the menstrual disorders. The increase in gonadotropin secretion that can be observed after ponderal recuperation suggests that malnutrition could be the most important mechanism involved in the decrease in gonadotropin secretion.The loss of fat tissue as a consequence of nutrient restriction has been associated with hypoleptinemia and abnormal secretion of peptides implicated in food control (neuropeptide Y, melanocortins and corticotropin-releasing factor, among others).A review of the endocrine abnormalities, disturbances in neurotransmitters, as well as a detailed analysis of bone markers and bone mineral density in patients with AN is described.