Reduction in the arginine vasopressin responses to metoclopramide and insulin-induced hypoglycemia in normal weight bulimic women.

A low plasma arginine vasopressin (AVP) responsiveness to hypertonic saline infusion has been described in bulimic women. At present, it is unknown whether this phenomenon is peculiar for the osmotic regulation of AVP secretion or whether it represents an aspect of a more general disorder of AVP secretion in bulimia nervosa. In order to answer these questions, in the present study the AVP responses to metoclopramide (MCP) (20 mg in an i.v. bolus) and insulin (0.15 IU/kg)-induced hypoglycemia were tested in normal weight bulimic women and in weight- and age-matched normal women. Basal AVP concentrations were similar in normal and bulimic women. In the normal controls, plasma AVP levels rose 2.6 times after MCP and 2.2 times in response to hypoglycemia. Both AVP increments were significantly lower in bulimic patients. In this group, plasma AVP levels rose 2 times after MCP and 1.8 times in response to hypoglycemia. When data of the MCP and insulin tolerance test were combined, regression analyses showed a significant positive correlation between AVP peak responses to MCP and hypoglycemia in the bulimic group. These data show an impaired AVP response to different releasing stimuli in bulimia, suggesting that a more general disorder than a simple change in the sensitivity to osmotic stimulation affects the AVP secretory system in bulimic patients. It is likely that bulimic subjects are affected by a neuroendocrine alteration in the control of AVP secretion, whose mechanisms are still unknown.