[Severe hyponatremia associated with anorexia nervosa: role of inappropriate antidiuretic hormone secretion?].

BACKGROUND: Anorexia nervosa may be revealed by hyponatremia or associated with it. This hyponatremia can be due to diuretics or laxatives abuse, potomania or inappropriate secretion of antidiuretic hormone as in the case reported here.

CASE REPORT: A 15 year-old girl was admitted for anorexia nervosa. She had secondary amenorrhea and asthenia and had lost 14 kg during the preceding 4 months. Her natremia ranged from 112 to 130 mEq/l with normal urinary sodium excretion, serum hypoosmolality (252 mosm/kg) and inappropriately elevated urinary osmolality (698 mosm/kg). Renal, adrenal and thyroid functions were normal. After water loading, patient remained euvolemic, with a negative free water clearance and an increased plasma ADH level with concomitant hyposmolality. A diagnosis of inappropriate secretion of antidiuretic hormone was made, after excluding other conditions such as potomania, drug abuse, vomiting, tumor and chronic lung disease.

CONCLUSIONS: Hyponatremia sometimes seen in anorexia nervosa must lead to the search of inappropriate antidiuretic hormone secretion.