ABSTRACT
INTRODUCTION: Anorexia nervosa (AN) is a disorder associated with many medical complications. Regarding phosphorus metabolism, the only recognized alteration is hypophosphatemia associated with refeeding syndrome. However, in our clinical practice, we have observed a high frequency of hyperphosphatemia in late phases of nutrition therapy in severely undernourished AN patients, which has barely been described. MATERIALS AND METHODS: We carried out a retrospective study of patients with AN hospitalized for severe decompensation of the disease. RESULTS: Eleven patients were included, all women, with a median age of 23 years [20-46] and a body mass index at admission of 12.2â¯kg/m2 [11.7-13.1]. Hyperphosphatemia was noted in 9 of the 11 cases (81.8%) with a median time to onset of 53 days [30-75]. The median peak serum phosphorus (P) level was 5.1â¯mg/dl [4.9-5.4]. An inverse relationship was found between the increase in P levels and phosphorus supplementation at the onset of admission. The magnitude of the P increase was associated with the body weight gain achieved during nutrition therapy. CONCLUSION: Late hyperphosphatemia during nutrition therapy in severely undernourished AN patients affects more than 80% of cases. Body weight gain throughout nutrition therapy is a predictor of increased P levels.