Impaired osmoregulation in anorexia nervosa: a case-control study.
BACKGROUND
Anorexia nervosa (AN) has been associated with abnormal osmoregulation and impaired urinary concentrating capacity. Conflicting results suggest that the disorder may be related to hypothalamic dysfunction and/or a primary renal defect. The role of antidepressants, which are increasingly prescribed in AN patients, has not been evaluated.


METHODS
We analysed renal function as well as electrolyte disturbances and osmoregulation parameters at baseline and following a water deprivation test in 12 well-defined AN patients (all females, 10 taking antidepressants) vs 12 age-matched controls and 11 young female patients taking antidepressants.


RESULTS
In comparison with matched controls, patients with AN were characterized by a significant alteration of osmoregulation both at baseline [lower plasma sodium and osmolality, abnormally high levels of antidiuretic hormone (ADH) and tendency towards more concentrated urine] and after water deprivation (impaired ADH reaction and lower urinary concentrating ability). The AN patients had no electrolyte abnormalities. The two patients with the shortest duration of AN showed a normal urinary concentrating ability. Patients taking antidepressants showed similar but less marked changes than AN patients, including a lower urinary concentrating ability.


CONCLUSIONS
These results show that AN patients are characterized by abnormal osmoregulation at baseline and a lack of reactivity of ADH with a significant urinary concentrating defect after water deprivation. The origin of these defects in AN patients is probably multifactorial, but the duration of the disease and the prescription of antidepressants could play a role.
Division of Internal Medicine, Saint-Luc Academic Hospital, Université Catholique de Louvain Medical School, B-1200 Brussels, Belgium.
Frédéric
F
Evrard
Mariana Pinto
MP
da Cunha
Michel
M
Lambert
Olivier
O
Devuyst
D000328:Adult; D000856:Anorexia Nervosa / Q000097:blood / Q000503:physiopathology*; D000928:Antidepressive Agents / Q000627:therapeutic use; D001827:Body Height; D015992:Body Mass Index; D001835:Body Weight; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D014667:Vasopressins / Q000097:blood; D014882:Water-Electrolyte Balance
D000928:Antidepressive Agents; D014667:Vasopressins