Growth hormone response to sodium valproate in chronic schizophrenia

The hypothesis of a gamma-aminobutyric acid (GABA) involvement in the pathophysiology of schizophrenia has been recently proposed but not confirmed. As GABA has been shown to affect basal growth hormone (GH) secretion in humans, the assessment of plasma GH response to a GABAergic drug, such as sodium valproate (SV), in schizophrenic subjects might be a tool with which to investigate central GABA activity in this illness. For this purpose, we administered orally 800 mg of SV or placebo to 13 chronic schizophrenics and to 10 normal controls, and measured plasma GH levels before and after the drug administration. SV enhanced basal GH secretion in healthy male volunteers, but not in chronic schizophrenics. These results suggest a defect of the endogenous GABA system in chronic schizophrenia. Whether the reduced responsiveness observed represents a primary defect or a secondary alteration of the GABA system in schizophrenia is as yet unknown.