Anorexia nervosa (AN) is a psychiatric diagnosis that describes an eating disorder characterized by low body weight and body image distortion with an obsessive fear of gaining weight. It is clear that there is no single cause of anorexia and that it stems from a mixture of social, psychological, and biological factors. Concerning biological factors, more and more data concerning hormones and neurotransmitters are available. It is well known that the corticotrope axis is disturbed in AN, with an excess of urinary free cortisol but with a maintained nychtemeral cortisol rhythm. This excess of cortisol may explain clinical symptoms like lanugo and osteoporosis and the sensation of well being observed in the disease. Beta-endorphin activity seems to be increased in AN, and induces tolerance to starvation. Catecholamines like dopamine and norepinephrine could be involved in the hyperactivity, reduced food intake, and amenorrhea observed in AN. Today, there are a lot of data about serotonin. High serotonin activity is linked to anxiety, sleep deprivation, excessive physical exercising, true anorexia (loss of appetite), a feeling of high power, and denial of nervous and physical exhaustion. However, treatment with serotonin inhibitors has failed to show a beneficial effect in AN patients. Thus, better understanding of the complex biological mechanisms involved in eating disorders is required, but because there is no single cause of AN, there is no evidence of the clinical efficacy of pharmacological treatment for the disease.
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