Reduction of GH response to the GABA-B agonist baclofen in patients with major depression.

In order to establish whether alterations in the GABAergic control of GH secretion occur in male patients with major depression, the GH response to the GABAergic-B agonist baclofen (10 mg PO at 0830h) or to placebo was tested in 9 depressed men and in 10 age- and weight-matched male normal controls. The basal concentrations of GH were significantly lower in the depressed patients (0.87 +/- 0.69 ng/ml) than in the normal controls (1.57 +/- 0.33 ng/ml) (p = 0.011) and were not modified by the administration of placebo. The administration of baclofen induced a striking, significant increase in GH concentrations in the normal controls (mean peak at 90 min = 6.4 +/- 1.5 ng/ml). In contrast, a slight, nonsignificant GH increase occurred in the depressed patients after baclofen (mean peak at 90 min = 1.57 +/- 1.45 ng/ml). The GH response was significantly lower in the depressed than in the control subjects (p less than 0.001). These data indicate the presence of reduced GABAergic control of GH secretion in male depressed patients.