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5-HTP (a serotonin precursor) has been shown in clinical studies to significantly increase GH release via serotoninergic pathways. A 1977 JCEM study (Lancranjan et al.) found a significant GH increase (p < 0.01) 30–120 minutes after IV 5-HTP infusion in both men and women, with a mean peak of 32.0 ± 8.8 ng/mL. Oral 5-HTP (200 mg) also demonstrated significant GH elevation in a clinical study in healthy adults.

Alpha-ketoglutarate (AKG), a key Krebs cycle intermediate, is a component of OKG and has been studied for its role in amino acid metabolism and anabolic hormone (including GH) secretion. As part of OKG, AKG contributes to the compound's established GH-stimulating properties. AKG's independent role in GH secretion is based partly on its metabolic precursor relationship to arginine and glutamine, which are documented GH secretagogues.

L-arginine is a well-established stimulant of pituitary growth hormone secretion, acting by suppressing endogenous somatostatin. AAKG's arginine moiety shares this property; acute arginine supplementation has been shown in RCTs to modestly increase GH levels. A 2022 systematic review and meta-analysis confirmed significant GH release with arginine supplementation alone.

D-aspartic acid accumulation in the anterior pituitary (adenohypophysis) has been shown in animal studies to stimulate secretion of growth-hormone releasing hormone (GHRH) and consequently growth hormone (GH). In vivo animal injection studies confirm D-Asp induces GH release. This mechanistic link is documented but direct human clinical trials specifically measuring GH endpoints after DAA supplementation are absent.

A clinical study in sprinters and long-distance runners demonstrated that creatine supplementation significantly increased GH levels after 6 weeks. Creatine is proposed to support GH indirectly through enhanced exercise performance and acute metabolic effects that stimulate pituitary GH release. This study and supporting references are cited in authoritative nutrition sources including Healthline and Examine.com.

D-Asp has been observed in animal and in vitro studies to stimulate growth hormone (GH) release from the pituitary gland. This is part of its broader neuroendocrine signaling role, acting upstream via hypothalamic GnRH stimulation and directly at the pituitary. Human clinical data specifically measuring GH responses to DAA supplementation are limited.

Multiple clinical trials have demonstrated that oral GABA supplementation (3 g) significantly elevates resting and post-exercise GH concentrations. A randomized double-blind crossover study (Powers et al., 2008, PMID 18091016) in 11 resistance-trained men found significant increases in immunoreactive and immunofunctional GH at rest and augmented exercise-induced GH. A 12-week RCT (Sakashita et al., JOCMR, 2019) showed elevated resting plasma GH at 4 and 8 weeks and greater fat-free mass gains with GABA plus whey vs. whey alone.

Multiple human clinical studies confirm that glycine infusion (4–12 g IV) produces dose-dependent increases in serum GH in normal subjects. Oral administration also demonstrated stimulatory effects. A 1978 study (Kasai et al., Metabolism) and a 1981 study (Baudry et al.) both showed significant GH elevation, with glycine described as 'one of the stimulatory agents inducing the pituitary gland to secrete hGH.'

GPC reliably stimulates growth hormone (GH) secretion in human studies. The mechanism involves ACh-mediated catecholamine release that amplifies pituitary GH response, particularly to exercise and GHRH. Effects have been demonstrated in both young and older adults.

L-arginine is the most extensively studied nutritional GH secretagogue. It suppresses endogenous somatostatin release from the hypothalamus, disinhibiting pituitary GH output. A 2022 systematic review and meta-analysis (PMC9712012) of randomized clinical trials found a significant mean GH increase (MD = 10.07 µg/L, 95% CI: 7.87–12.28) with arginine alone, with even greater responses when combined with GHRH. Oral doses of ~10 g have produced modest but statistically significant GH elevations in resting adults.

An early clinical study found that a 2 g oral dose of L-glutamine transiently elevated GH levels by up to 78% in healthy subjects. A randomized double-blind trial using a mixture of glycine, glutamine, and niacin increased serum GH by ~70% vs. placebo over 3 weeks in middle-aged adults. L-glutamine is thought to act via hypothalamic and pituitary pathways to stimulate GH secretion.

Oral glycine administration acutely stimulates pituitary growth hormone (GH) secretion in a dose-dependent manner. A bolus of 22.5 g has been reported to cause a ~60% surge in GH levels within minutes. Smaller doses of 4–12 g also raise serum GH in a dose-dependent fashion, per early pharmacological studies.

L-lysine, especially when combined with L-arginine, has been shown in clinical studies to significantly increase GH secretion in resting subjects. One study of 15 healthy males found that the combination of arginine pyroglutamate and L-lysine significantly elevated GH compared to either amino acid alone. Lysine alone at lower doses (1,200 mg) did not reliably raise GH, but synergistic effects with arginine are documented.

L-ornithine is an amino acid that has been shown to augment post-exercise GH levels. A 2010 clinical study found that L-ornithine (100 mg/kg) administered 30 minutes after exercise produced a significantly greater GH peak compared to controls. L-ornithine is also a component of OKG, which has documented GH-stimulating activity in clinical nutritional studies.

Melatonin, the pineal gland hormone, is documented in multiple clinical studies to stimulate GH secretion in humans. A 1993 Clinical Endocrinology RCT (Valcavi et al.) showed oral melatonin (10 mg) approximately doubled GHRH-stimulated GH release and increased basal GH through pathways involving somatostatin suppression. Exogenous oral melatonin at both 0.5 mg and 5.0 mg has been shown to produce significant increases in plasma GH concentrations.

Ornithine alpha-ketoglutarate (OKG), a salt of two ornithine molecules and one alpha-ketoglutarate molecule, has been associated with GH and insulin secretion in enteral and parenteral nutrition studies. When fed enterally to trauma and burn patients, OKG significantly increased both IGF-1 and GH levels. Its anabolic mechanism involves generating glutamine and arginine, both of which are independent GH secretagogues.

Dopamine stimulates growth hormone (GH) secretion from the anterior pituitary via hypothalamic GHRH and dopamine receptors. L-DOPA (the active principle in MP) has been documented in clinical pharmacology studies to stimulate GH secretion in humans, a mechanism used in GH stimulation testing. A blend of MP and Chlorophytum borivilianum in exercise-trained men raised serum GH. However, direct RCTs using MP alone for GH augmentation are limited.

Zinc has documented effects on the GH–IGF-1 axis. Clinical trials in prepubertal children show that zinc supplementation raises serum IGF-1 and IGFBP-3 levels. The effect is most pronounced in zinc-deficient populations and with doses ≤10 mg/day over more than 8 weeks. Zinc appears to act downstream of GH secretion, directly stimulating IGF-1 production rather than altering pituitary GH output.

Anterior pituitary glandular supplements have been traditionally theorized to support growth hormone output, based on the gland's role as the exclusive source of endogenous GH. Early glandular therapy texts and contemporary naturopathic sources cite this application. Human clinical data for the oral supplement form are absent.