Few organ systems are spared the progressive deterioration seen in critically ill patients with anorexia nervosa. Most of the endocrine disturbances discussed are due to starvation and represent appropriate metabolic adaptation of the body to food restriction and negative energy balance. In a starving patient, a lowered metabolic rate, increased cortisol and growth hormone level and reduced fertility are all appropriate adaptations to an abnormal and highly stressful state. Most metabolic abnormalities can be reversed with a well-planned refeeding program and nutritional recovery.