Effect of clonidine on growth hormone release in psychiatric patients and controls

The stimulation of human growth hormone (HGH) release by clonidine (0.15 mg i.v.) was studied as a test of the postsynaptic alpha-receptor sensitivity of psychiatric patients. In this test, endogenous depressives showed a significantly reduced HGH response to clonidine as compared to normal controls, neurotic-reactive depressives, and schizophrenics. However, no differences were found between the endogenous depressives and a group of schizoaffective patients. HGH response to clonidine was not correlated with plasma levels of noradrenaline, serum cortisol, free fatty acids, or blood glucose. Within the group of normal control subjects, a reduced HGH response was found in most postmenopausal women and in some regular users of alcohol. Our findings suggest that patients with endogenous depression are characterized by a subsensitivity of postsynaptic alpha-receptors or of structures related to them. The clonidine test shows promise as an indicator of vulnerability to endogenous depression.