Growth hormone response to apomorphine in panic disorder: comparison with major depression and normal controls

Several lines of evidence suggest that dopamine might be involved in anxiety states. In the present study we assessed the growth hormone (GH) response to 0.5 mg apomorphine (a dopaminergic agonist) in 10 male drug-free inpatients meeting Research Diagnostic Criteria for panic disorder who were compared with 10 male major depressive inpatients and 10 male normal controls. The three groups differed significantly in the GH peak response (mean +/- SD): 27.8 +/- 12.5 ng/ml in panics, 5.4 +/- 4.0 ng/ml in major depressives, and 25.8 +/- 11.3 ng/ml in normal controls (F(2,27) = 15.3; P = 0.00003). Although there were significant differences between panics and major depressives (P = 0.00004), and between major depressives and controls (P = 0.00004), panics did not significantly differ from controls. These results do not support the hypothesis of an overlap between panic and affective disorders, and suggest that the hypothalamo-GH-somatomedin axis could be intact in panic disorder.