Hypophosphatemia during starvation in anorexia nervosa

Patients with anorexia nervosa frequently complain of somatic distress, usually from multiple causes. Depression, for example, may cause weakness, fatigue, and decreased appetite. Vomiting or diuretic/laxative abuse result in weakness and fatigue, probably by hypokalemia, volume contraction, and other mechanisms. Significant hypophospahatemia should also now be considered as a cause of the weakness and fatigue in anorexia nervosa but has not previously been reported in pure restricting anorexia nervosa. Hypophosphatemia not only may mimic symptoms seen with anorexia nervosa, but if chronic can cause osteomalacia, pertinent for anorexics already at high risk for premature osteoporosis. We report one patient with symptomatic hypophosphatemia during starvation in anorexia nervosa who improved with repletion of phosphate and two others retrospectively noted to be hypophosphatemic. No etiology, other than starvation, was detected. Serum phosphorus should be measured in all patients with anorexia nervosa. Symptoms should not merely be attributed to depression or hypokalemia.