Growth hormone response to clonidine stimulation in depressive states — First part of a two-part study —

Abstract

Summary31 patients presenting a Major Depressive Episode were divided into two groups (endogenous versus neurotic depression), in keeping with the Newcastle criteria (Garside and Roth, 1974). 10 patients were allocated to each group for the realization of a test of growth hormone (GH) response to clonidine stimulation.The patients received no psychotropes for 8 days prior to the test. Mean age for the neurotic and endogenous groups was respectively 36.67 ± 3.18 years and 44.71 ± 2.56 years. Severity of depression, assessed with the Hamilton rating scale (21 items), was comparable in the two groups (35.35 ± 4.12 versus 39.8 ± 6.13).The test was carried out in two phases in each patient. During the initial phase, saline was infused over 10 minutes and continuous sampling was realized over a 4-hour period (automatic fraction collector with peristaltic pump), at between 9 AM and 1 PM. 48 hours later, the same procedure was repeated with the addition of 15 µg clonidine. This procedure allowed partial neutralization, for interpretation of results, of the «test apprehension» effect. Assays were carried out by radioimmunoassay (pooled samples), and correspond to real values for 10-minute time intervals (integrated values).Spontaneous GH secretion in the endogenous group was significantly lower (0.57 ± 0.16 ng/ml) than in the neurotic group (5.03 ± 1.08 ng/ml) and the control group (2.47 ± 0.78 ng/ml). After clonidine stimulation, GH response in the neurotic group was identical to that in the control group. No significant response was observed in the endogenous group. These results confirm those of several previous studies (Matussek, Charney, Checkley, Boyer, Corn, Siever) and seem to indicate hyposensitivity of the post-synaptic α2-adrenergic receptors in endogenous depression. Nevertheless, spontaneous GH hyposecretion in the same patients necessarily involves other mechanisms. The hypotheses concerning these mechanisms will be discussed in the second part of this study.