Gamma-aminobutyric acid (GABA) is the brain’s principal inhibitory neurotransmitter — the chemical messenger that calms neural activity, reducing anxiety and promoting relaxation and sleep. Some athletes and bodybuilders take GABA supplements in the belief that it stimulates growth hormone release and aids recovery, marketing it as a “secretagogue” that triggers hormone secretion. The pharmacology is doubtful: GABA taken orally crosses the blood-brain barrier poorly, so little reaches the brain, and evidence for meaningful increases in growth hormone or performance is weak. Supplemental GABA is generally considered safe at typical doses, though it can cause tingling, drowsiness, or drops in blood pressure. Its sporting use rests more on marketing than on physiology.