Rosh Psychiatry Board Practice Exam

What is the hallmark and predominant cause of refeeding syndrome in a patient with anorexia nervosa?

1. Hypokalemia

2. Thiamine deficiency

3. Hypophosphatemia

4. Congestive heart failure

The correct answer is: Hypophosphatemia

Refeeding syndrome is a serious condition that occurs when feeding is restarted in individuals who are malnourished, such as patients with anorexia nervosa. The hallmark of refeeding syndrome is the rapid shift of electrolytes and fluids in the body, particularly involving phosphorus levels. When a patient with anorexia is reintroduced to carbohydrates too quickly, insulin secretion increases, leading to a cellular uptake of electrolytes, especially phosphorus, potassium, and magnesium from the bloodstream into cells to support cellular metabolism. This causes serum levels of phosphorus, which is essential for many vital cellular functions like ATP production, to fall significantly, leading to hypophosphatemia. Hypophosphatemia can result in severe complications including muscle weakness, respiratory failure, and cardiovascular issues. Thus, the predominant cause of refeeding syndrome, particularly in the context of anorexia nervosa, is this drastic drop in phosphate levels due to the metabolic response to refeeding.