Abstract

BACKGROUND The growth hormone (GH) response to apomorphine, thought to reflect central dopaminergic receptor sensitivity, has been reported as enhanced in acute schizophrenia. We investigated this response in relation to the psychotic episodes associated with Parkinson's disease (PD).

METHOD The GH response to apomorphine was measured in three groups of patients with Parkinson's disease: those currently psychotic (n = 9), those with a past history of psychosis (n = 7) and those who had never been psychotic (n = 8).

RESULTS Apomorphine-induced GH response was not related to psychosis but was unexpectedly associated with measures of depression.

CONCLUSIONS Visual hallucinations were a prominent feature in the psychotic patients and the atypical nature of these psychoses might explain why we found no evidence of dopaminergic sensitivity. Serotonergic dysfunction would be in keeping with this. Dopaminergic mechanisms may contribute to the minor depressive symptomatology seen in PD.