GABA, Gamma Aminobutyric Acid, is an amino acid classified as a neurotransmitter (A neurotransmitter is a substance that transmits nerve impulses across a synapse. A synapse is a region where nerve impulses are transmitted across axon terminals.) GABA's high concentration in the hypothalamus suggests this amino acid plays a significant role in hypothalamic-pituitary function. The hypothalamus is a region of the posterior section of the brain and is the regulating center for visceral (instinctive) functions such as sleep cycles, body temperature, and the activity of the pituitary gland. The pituitary gland is the master endocrine gland affecting all hormonal functions of the body. One primary hormone of concern to the athlete is growth hormone (GH) and its various hormonal constituents.
The amino acid GABA has been shown in numerous studies to promote significant increases in plasma growth hormone levels.
There have been literally hundreds of clinical studies on GABA and numerous studies on GABA's ability to elevate growth hormone levels. As with most nutritional studies, GABA research has come directly from the medical community. One noted study from the First Medical Clinic at the University of Milan in Milan, Italy titled, "Effect of acute and repeated administration of gamma aminobutyric acid (GABA) on growth hormone and prolactin secretion in man", shows just how effective GABA is.
Quoted results from this study showed "In all of the 19 subjects studied, compared with 18 controls, plasma growth hormone levels were significantly increased (above 5 ng/ml) by acute oral administration of 5 g of GABA."
This study showed over a 5 1/2 fold increase in plasma growth hormone levels 90 minutes after GABA administration. That is a significant increase unmatched by any other nutritional means.
Most cited studies on amino acids and growth hormone elevation utilize intravenous delivery means. This is unrealistic and doesn't reflect real world results. Studies on GABA have been performed with both oral and intravenous administration with the oral route showing remarkable effectiveness.
GABA's growth hormone elevating effects rival that of potent pharmaceutical compounds.
References:
1. Involvement of growth hormone-releasing factor in growth hormone secretion induced by gamma-aminobutyric acid in conscious rats. Murakami Y, 1985 Endocrinology 117(2), 787-789 (1985)
2. Evidence for a GABAergic control of the exercise-induced rise in GH in man. Steardo L, Iovino M, Monteleone P, Agrusta M, Orio F Eur J Clin Pharmacol 28 (5): 607-609 (1985)
3. Growth hormone secretion of the neonatal rat pituitaries is stimulated by gamma-aminobutyric acid in vitro. Acs Z, Makara GB, Stark E Life Sci 34 (16): 1505-1511 (Apr 1984)
4. Gamma aminobutyric acid (GABA), a modulator of anterior pituitary hormone secretion by hypothalamic and pituitary action. McCann SM, Vijayan E, Negro-Vilar A, Mizunuma H, Mangat H Psychoneuroendocrinology 9 (2): 97-106 (1984)
5. Effect of gamma-aminobutyric acid on growth hormone and prolactin secretion in man: influence of pimozide and domperidone. Cavagnini F, Benetti G, Invitti C, Ramella G, Pinto M, Lazza M, Dubini A, Marelli A, Muller EE J Clin Endocrinol Metab 51 (4): 789-792 (Oct 1980)
6. Effects of some gamma-aminobutyric acid (GABA)-ergic drugs on the dopaminergic control of human growth hormone secretion. Koulu M, Lammintausta R, Dahlstrom S J Clin Endocrinol Metab 51 (1): 124-129 (Jul 1980)
7. 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 Acta Endocrinol (Copenh) 93 (2): 149-154 (Feb 1980)
"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."
8. Growth hormone release by gamma-aminobutyric acid (GABA) and gamma-amino-beta-hydroxybutyric acid (GABOB) in the rat. Abe H, Kato Y, Chihara K, Ohgo S, Iwasaki YEndocrinol Jpn 24 (2): 229-231 (Apr 1977)
9. Regulation of growth hormone secretion Kato Y, Chihara K, Daigo S, Iwasaki Y, Abe H Horumon To Rinsho 25 (2): 131-141 (Feb 1977)
10. Pharmacological evidence for a dual GABAergic regulation of growth hormone release in humans. Steardo L, Iovino M, Monteleone P, Agrusta M, Orio F Life Sci 39 (11): 979-985 (Sep 1986)
11. Involvement of alpha-adrenergic and GABAergic mechanisms in growth hormone secretion induced by central somatostatin in rats. Murakami Y, Kato Y, Koshiyama H, Inoue T, Ishikawa Y, Imura H Brain Res 407 (2): 405-408 (Mar 1987)
12. Evidence for a sex difference in the basal growth hormone response to GABAergic stimulation in humans. Monteleone P, Maj M, Iovino M, Steardo L Acta Endocrinol (Copenh) 119 (3): 353-357 (Nov 1988)
13. Role of hypothalamic factors (growth-hormone-releasing hormone and gamma-aminobutyric acid) in the regulation of growth hormone secretion in the neonatal and adult rat. Acs Z, Lonart G, Makara GB Neuroendocrinology 52 (2): 156-160 (Aug 1990)
14. Possible mediation of GABA induced growth hormone secretion by increased calcium-flux in neonatal pituitaries. Acs Z, Zsom L, Makara GB Life Sci 50 (4): 273-279 (1992)
15. Potent agonists of growth hormone-releasing hormone. II. Zarandi M, Serfozo P, Zsigo J, Deutch AH, Janaky T, Olsen DB, Bajusz S, Schally AV Pept Res 5 (4): 190-193 (Jul 1992)
16. New Gaba-containing analogues of human growth hormone-releasing hormone (1-30)-amide: I. Synthesis and in vitro biological activity. Mezo I, Kovacs M, Szoke B, Szabo EZ, Horvath J, Makara GB, Rappay G, Tamas J, Teplan I J Endocrinol Invest 16 (10): 793-798 (Nov 1993)
17. Neuroendocrine regulation of growth hormone secretion in sheep. VII. Effects of GABA. Spencer GS, Berry CJ, Bass JJ Regul Pept 52 (3): 181-186 (Aug 1994)
18. Growth hormone secretion and activation of cyclic AMP by growth hormone releasing hormone and gamma-aminobutyric acid in the neonatal rat pituitary. Mergl Z, Acs Z, Makara GB Life Sci 56 (8): 579-585 (1995)