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

Rationale: Growth hormone (GH) response to a challenge with a GABA(B) recep tor agonist, baclofen, is considered to provide an in vivo index of hypotha lamic GABA(B) receptor function in humans. Objectives: The purpose of this study was to explore the role of GABA(B) receptors in the pathophysiology o f mania by measuring plasma GH response to baclofen in ten manic patients a nd ten matched healthy controls. Methods: After obtaining blood samples fur baseline GH levels, a single dose of 20 mg baclofen was administered orall y to all the subjects, and further blood samples were obtained at 30-min in tervals for the following 3 h. Results: We found that baclofen administrati on led to a significant increase in GH release both in manic patients and h ealthy controls, but the GH response to baclofen in manic patients was sign ificantly enhanced when compared to healthy controls. Conclusions: Our resu lts 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.