In the few human studies that exist, a single oral dose of GABA (3–5 grams) was found to increase circulating growth hormone concentrations at rest[1][2][3] and in response to resistance exercise.[3] An increase in resting growth hormone concentrations has also been found in participants with no health conditions following intravenous injection with baclofen, a drug that activates GABAB receptors,[4] but not alprazolam, a GABAA receptor activator.[5][6] However, the growth hormone-increasing effects of GABA[2] and baclofen[7] attenuate with daily use.
Overall, the effects of GABA on circulating growth hormone concentrations are complex. Although high-dose supplementation with GABA can significantly increase growth hormone levels, the effects attenuate rapidly, within a few days.[2] It is not currently clear whether the effects of GABA on human growth hormone have meaningful effects on health or athletic performance.