Pubmed... naturally, duhBald Gorilla said:Where the hell are these "studies" that say it increase GH by 500%???
It made my tongue swell up! A little scary...

EDIT:
Personally I think it's pretty worthless even if the results of studies like this are legit. Lots of things raise GH briefly. Won't make you jacked. Glutamine is another amino that may increase GH so if you are using it just take a teaspoon before bed.Acta Endocrinol (Copenh). 1980 Feb;93(2):149-54.
Effect of acute and repeated administration of gamma aminobutyric acid (GABA) on growth hormone and prolactin secretion in man.
Cavagnini F, Invitti C, Pinto M, Maraschini C, Di Landro A, Dubini A, Marelli A.
A single oral dose of 5 g gamma aminobutyric acid (GABA) was given to 19 subjects and serial venous blood samples were obtained before and 3 h after drug administration. A placebo was administered to 18 subjects who served as controls. GABA caused a significant elevation of plasma growth hormone levels (P less than 0.001), but did not consistently alter plasma prolactin concentration since only 5 out of 15 subjects showed an increase of the hormone. Eight additional subjects were submitted to an insulin tolerance test before and after per os administration of 18 g GABA daily for 4 days. Protracted GABA treatment significantly blunted the response of growth hormone and enhanced that of prolactin to insulin hypoglycaemia (P less than 0.01). These results indicate that pharmacological doses of GABA affect growth hormone and prolactin secretion in man. The precise nature of GABA's effects as well as its mechanism of action remains to be clarified.