Anorexia nervosa: hypogonadotrophic hypogonadism and bone mineral density.

Anorexia nervosa is a chronic illness that involves a reduction in caloric intake, loss of weight and amenorrhoea, either primary or secondary. In addition to prolonged amenorrhoea, osteopenia and osteoporosis are the most frequent complications. Patients exhibit an alteration in the hypothalamic-pituitary-gonadal axis, which is responsible for the menstrual disorders. The increase in gonadotrophin secretion that can be observed after ponderal recuperation suggests that malnutrition could be the most important mechanism involved in the decrease in gonadotrophin secretion. The loss of fat tissue, as a consequence of the restriction of nutrients, has been associated with hypoleptinaemia, abnormal secretion of peptides implicated in food control (neuropeptide Y, melanocortins and corticotrophin-releasing hormone, among others) and diminution of the amount of total body fat. Despite oestrogen therapy, the severe loss of bone mass may progress. Other factors such as weight loss, duration of amenorrhoea and low insulin-like growth factor-I (IGF-I) levels could contribute to the loss of bone mass in women with anorexia nervosa. The recuperation of weight and, in particular, the amount of total body fat could lead to the spontaneous recuperation of menstruation.