α2-Adrenergic receptor sensitivity in panic disorder: I : GH response to GHRH and clonidine stimulation in panic disorder

Baseline levels of GH and somatomedin C (SmC) and GH responses to GHRH (1 μg/kg b.w.) and to clonidine (150 μg) were measured in 10 outpatients with panic disorder before and after 30 days of 2–2.5 mg of alprazolam therapy, and in 10 psychophysically healthy controls. Basal levels of GH were normal in the patients and those of SmC significantly elevated, both before and after therapy. Basal GH responses to GHRH stimulation were normal and did not change after alprazolam treatment. Basal GH responses to clonidine stimulation were blunted in the patients and improved after therapy, in parallel with an amelioration of the psychopathology. Our data suggest that adrenoceptor sensitivity, investigated by the clonidine test, is reduced in panic disorder.