Elevated response of growth hormone to graded doses of apomorphine in schizophrenic patients

Three different dosages of apomorphine (0.003 mg/kg, 0.006 mg/kg, 0.012 mg/kg) were administered to stimulate the release of growth hormone (GH) in 16 male schizophrenic patients (age: 30.6, SD: 8.1 years) and 12 healthy male controls (age: 29, SD: 3.2 years). Results showed a significantly higher GH response (P < 0.01) after stimulation with 0.006 mg/kg apomorphine (APO). In contrast, stimulation with 0.012 apomorphine was unable to distinguish patients from normal controls. The results support the hypothesis of an increased dopaminergic receptor sensitivity in the hypothalamic-pituitary system of acute schizophrenic patients. This disturbance of dopaminergic neurotransmission could be observed only after a stimulation with low doses of apomorphine.