Insulin response in bulimia nervosa as a marker of nutritional depletion.

OBJECTIVE: The aim of this provocation study was to examine insulin, glucose, and cortisol levels in response to a glucose load in bulimia nervosa patients and to relate this to behavior, treatment status, and depressive symptomatology.
METHOD: A 3-hr glucose tolerance test was performed in 15 female patients and in 4 controls. Tests were performed at different stages of treatment and following documented engagement in the patient's usual or previous repertoire of bulimic behaviors in the 24 hr prior to testing. Insulin, glucose, and cortisol levels were assayed at baseline and at 30-min intervals following the glucose load. Presence or absence of significant depressive symptomatology was ascertained.
RESULTS: Three patterns of insulin response were identified: (1) an exaggerated response, (2) a normative response which resembled that of healthy controls, and (3) a blunted pattern. A reciprocal relationship between peak insulin and mean cortisol levels was seen with higher depression scores associated with blunted insulin response. Patients whose response was exaggerated binged and vomited relatively infrequently and were of stable weight. The insulin response of successfully treated patients, abstinent from binging and vomiting for 4 weeks, was similar to that of normal controls. A blunted response occurred in patients who binged and vomited more frequently, whose weight was unstable, and whose baseline eating was chaotic or nonexistent. DISCUSSION: The exaggerated insulin response was seen as a physiological adaptation to intermittent starvation reversible with treatment, while the blunted insulin response associated with higher cortisol levels was seen to result from more constant nutritional deprivation secondary to greater disturbance of behavior.