REDUCTION IN THE ARGININE-VASOPRESSIN RESPONSES TO METOCLOPRAMIDE ANDINSULIN-INDUCED HYPOGLYCEMIA IN NORMAL-WEIGHT BULIMIC WOMEN

A low plasma arginine vasopressin (AVP) responsiveness to hypertonic s aline 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 thes e 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 hypogl ycemia were tested in normal weight bulimic women and in weight- and a ge-matched normal women. Basal AVP concentrations were similar in norm al 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 grou p, 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 correlatio n between AVP peak responses to MCP and hypoglycemia in the bulimic gr oup. These data show an impaired AVP response to different releasing s timuli in bulimia, suggesting that a more general disorder than a simp le change in the sensitivity to osmotic stimulation affects the AVP se cretory system in bulimic patients. It is likely that bulimic subjects are affected by a neuroendocrine alteration in the control of AVP sec retion, whose mechanisms are still unknown.