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Growth hormone isoform responses to GABA ingestion at rest and after exercise.

Powers ME, Yarrow JF, McCoy SC, Borst SE.

Division of Athletic Training, Shenendoah University, Winchester, VA 22601, USA. mpowers@su.edu

Abstract

Oral administration of the amino acid/inhibitory neurotransmitter gamma aminobutyric acid (GABA) reportedly elevates resting serum growth hormone (GH) concentrations. PURPOSE: To test the hypothesis that GABA ingestion stimulates immunoreactive GH (irGH) and immunofunctional GH (ifGH) release at rest and that GABA augments the resistance exercise-induced irGH/ifGH responses. METHODS: Eleven resistance-trained men (18-30 yr) participated in this randomized, double-blind, placebo-controlled, crossover study. During each experimental bout, participants ingested either 3 g of GABA or sucrose placebo (P), followed either by resting or resistance exercise sessions. Fasting venous blood samples were acquired immediately before and at 15, 30, 45, 60, 75, and 90 min after GABA or P ingestion and were assayed for irGH and ifGH. RESULTS: At rest, GABA ingestion elevated both irGH and ifGH compared with placebo. Specifically, peak concentrations of both hormones were elevated by about 400%, and the area under the curve (AUC) was elevated by about 375% (P

PMID: 18091016 [PubMed – indexed for MEDLINE]