A 17-year-old girl is admitted to the hospital due to purging behavior, weight loss, and syncope. Nasogastric feeds are initiated, and her activities are restricted. On the second day of admission, the patient reports severe shortness of breath and has recurrent episodes of nonsustained ventricular tachycardia. Blood pressure is 82/55 mm Hg, pulse is 112/min, and respirations are 22/min. BMI is 14 kg/m². Physical examination shows an emaciated girl with bibasilar crackles and jugular venous distension. Serum chemistry results are as follows: A marked increase in which of the following hormones best explains this patient's deterioration?

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11ec25c8_d3cc_bde5_bc81_39fceb0c4e97_MD0003_00 This patient with anorexia nervosa developed severe electrolyte abnormalities, cardiac arrhythmias, and evidence of congestive heart failure (ie, increased pulse and respiratory rate, jugular venous distension, bibasilar lung crackles) after beginning tube feeding. This presentation is consistent with acute refeeding syndrome, a potentially life-threatening complication of the reintroduction of nutrition in patients with anorexia nervosa. Refeeding syndrome is the constellation of pathologic derangements resulting from increased insulin activity as the body shifts from a state of prolonged catabolism to anabolism. Carbohydrate ingestion, whether enteral or intravenous, causes pancreatic insulin secretion and cellular uptake of phosphorus, potassium, and magnesium, leading to serum electrolyte deficiencies. Phosphorus is the primary deficient electrolyte because it is required for energy (in the form of ATP). Deficiencies in potassium and magnesium potentiate cardiac arrhythmias in a heart that is already atrophic from prolonged malnutrition. Therefore, aggressive initiation of nutrition without adequate electrolyte repletion can rapidly precipitate congestive heart failure (eg, jugular venous distension, pulmonary crackles, tachypnea, as seen in this patient). Other common complications involve the muscular (eg, weakness, rhabdomyolysis), gastrointestinal (eg, diarrhea, elevated transaminases), and neurologic (eg, tremor, seizure) systems. (Choices A and B) Aldosterone and cortisol stimulate water resorption, sodium conservation, and potassium secretion to maintain blood pressure. These steroid hormones are high during starvation but less so during refeeding. In addition, they do not directly impact phosphorus or magnesium uptake. (Choice C) Glucagon activity is elevated during starvation but decreased during refeeding. (Choice E) Patients with anorexia nervosa have euthyroid hypothyroxinemia, which is characterized by normal TSH and normal to decreased serum thyroxine and triiodothyronine. Educational objective: Refeeding syndrome is a potentially fatal complication of nutritional rehabilitation in anorexia nervosa. Carbohydrate intake stimulates insulin activity, which in turn promotes cellular uptake of phosphorus, potassium, and magnesium, leading to electrolyte deficiency. Cardiac manifestations include arrhythmias and congestive heart failure. Other common complications involve the muscular (eg, weakness, rhabdomyolysis), gastrointestinal (eg, diarrhea, elevated transaminases), and neurologic (eg, tremor, seizure) systems. References: Nutritional rehabilitation: practical guidelines for refeeding the anorectic patient. (http://www.ncbi.nlm.nih.gov/pubmed/20798756) Hypophosphatemia during nutritional rehabilitation in anorexia nervosa: implications for refeeding and monitoring. (http://www.ncbi.nlm.nih.gov/pubmed/12507806)

A 17-Year-Old Girl Is Admitted to the Hospital Due to Purging