Which electrolyte disturbance is commonly associated with dehydration in anorexia nervosa?

• A. Hyperkalemia
• B. Hypokalemia
• C. Hypernatremia
• D. Hyponatremia

Answer: (B)

Potassium depletion from purging and volume loss is a classic electrolyte disturbance seen with dehydration in anorexia nervosa. Vomiting or laxative abuse causes direct loss of potassium in the GI tract, and the resulting volume depletion activates the renin-angiotensin-aldosterone system, which promotes potassium excretion in the distal nephron. Combined with poor dietary potassium intake, this leads to low serum potassium, or hypokalemia. This matters clinically because hypokalemia can cause muscle weakness and dangerous cardiac arrhythmias. Hyperkalemia would point to renal failure or tissue breakdown, hypernatremia to pure water loss, and hyponatremia to excess free-water intake or other disorders—none as tightly linked to dehydration from anorexia nervosa as hypokalemia.