AVP and Hyponatremia: Goldman et al demonstrated a reduced threshold for AVP secretion and increased sensitivity to its actions in patients with psychosis with primary polydipsia and hyponatraemia.6 The threshold for AVP release has also been shown to be exacerbated by psychosis in patients with schizophrenia with hyponatremia and polydipsia.7 One MRI study in humans showed decreased anterior hippocampal volume in patients with hyponatraemic schizophrenia linking an altered structural anatomy to this clinical feature.8