Neurohypophyseal dysfunction: implications for the pathophysiology of eating disorders.

Vasopressin (AVP) and oxytocin (OT) are hypothalamic neuropeptides having distinct peripherally and centrally directed cell populations. While principally responsible for the regulation of osmotic equilibrium, AVP also participates in stress-mediated adrenocorticotropic hormone (ACTH) release, and in consolidation and retrieval of aversively conditioned behaviors. OT is principally known for its role in parturition and lactation, but also has effects opposite of AVP, antagonizing stress-mediated ACTH release and impairing the consolidation and retrieval of aversively conditioned behaviors. Our group has demonstrated novel peripheral osmoregulatory defects in underweight anorexics, coupled with hypersecretion of AVP into the cerebrospinal fluid (CSF). Conversely, a relative reduction of CSF OT is seen in underweight anorexics. Speculatively, these reciprocal changes in neurohypophyseal peptides in the underweight anorexic may enhance the observed neuroendocrine and cognitive abnormalities. In addition, the alterations in CSF OT may occur as a consequence of the abnormal gastrointestinal function present during the acute stages of anorexia nervosa.