Growth hormone response to baclofen in patients with mania: a pilot study

Abstract 

Rationale: Growth hormone (GH) response to a challenge with a GABA_B receptor agonist, baclofen, is considered to provide an in vivo index of hypothalamic GABA_B receptor function in humans. Objectives: The purpose of this study was to explore the role of GABA_B receptors in the pathophysiology of mania by measuring plasma GH response to baclofen in ten manic patients and ten matched healthy controls. Methods: After obtaining blood samples for baseline GH levels, a single dose of 20 mg baclofen was administered orally to all the subjects, and further blood samples were obtained at 30-min intervals for the following 3 h. Results: We found that baclofen administration led to a significant increase in GH release both in manic patients and healthy controls, but the GH response to baclofen in manic patients was significantly enhanced when compared to healthy controls. Conclusions: Our results suggest that manic patients may have an up-regulated hypothalamic GABA_B receptor function. However, in light of the limitations including small sample size and absence of placebo control, our results should be viewed as preliminary. Further studies with a larger number of manic patients and a placebo control design are needed to replicate our finding before any firm conclusion can be drawn.