GHRP-6: Scientific Profile

Publicado el 12 de julio de 2026 · Actualizado el 28 de agosto de 2026

GHRP-6 (CAS 87616-84-0, development code SKF-110679) is a synthetic hexapeptide growth-hormone secretagogue, used in research for its ability to activate the secretagogue receptor (GHS-R1a, the ghrelin receptor) and to induce pulsatile release of GH from the pituitary. It is used as a laboratory tool to study the somatotropic axis, ghrelin signaling, and appetite regulation.

GHRP-6 (Growth Hormone Releasing Peptide-6) is a synthetic six-amino-acid peptide with the sequence His-D-Trp-Ala-Trp-D-Phe-Lys-NH2, also identified by its development code SKF-110679 and by CAS number 87616-84-0. Its molecular formula is C46H56N12O6 and its molecular weight is approximately 873.03 g/mol. It belongs to the class of growth hormone secretagogues (GH secretagogues), a group of molecules capable of stimulating GH secretion through a mechanism distinct from that of growth hormone-releasing hormone (GHRH). It is one of the earliest and most studied representatives of this family, and its characterization was key to the pioneering work on GH-releasing peptides carried out largely by Cyril Bowers' group, whose research helped delineate the signaling pathway that years later would lead to the discovery of the secretagogue receptor and its endogenous ligand, ghrelin.

Structurally, GHRP-6 is a hexapeptide that incorporates two residues in the D configuration (D-tryptophan and D-phenylalanine), which confers greater resistance to degradation by peptidases compared with peptides formed exclusively of L-amino acids. The C-terminus is amidated (Lys-NH2), a feature that also contributes to its stability and its affinity for the receptor. These non-natural modifications make GHRP-6 a useful tool in research models where sustained and reproducible activation of the secretagogue pathway is sought.

From the standpoint of the mechanism of action, GHRP-6 acts as an agonist of the growth hormone secretagogue receptor type 1a (GHS-R1a), the same G protein-coupled receptor that is endogenously activated by ghrelin. Activation of GHS-R1a in the somatotropic cells of the anterior pituitary and in the hypothalamus triggers the phospholipase C pathway, with generation of inositol trisphosphate (IP3) and diacylglycerol, mobilization of intracellular calcium, and pulsatile release of stored GH. GHRP-6 acts synergistically and complementarily with GHRH: while GHRH operates mainly through the cyclic AMP pathway, GHRP-6 does so through the calcium-dependent pathway, so that the combination of both stimuli produces in experimental models a GH response greater than the sum of their separate effects. Additionally, in preclinical models GHRP-6 modulates somatostatin signaling, the main physiological brake on GH secretion, attenuating its inhibitory effect. Because GHS-R1a also participates in hypothalamic circuits of appetite regulation, GHRP-6 is notably orexigenic in animal models: its administration is characteristically associated with a marked increase in feeding behavior, a trait that distinguishes it from other secretagogues such as ipamorelin, which is more selective for GH.

The documented research applications of GHRP-6 are concentrated along several axes. First, it has served as a pharmacological tool to characterize the somatotropic axis and to test pituitary GH reserve in stimulation protocols in experimental models, both alone and in combination with GHRH. Second, it has been fundamental in dissecting the biology of the ghrelin receptor: much of what is understood today about GHS-R1a comes from studies that used GHRP-6 as a reference agonist both before and after the identification of ghrelin as the natural ligand. Third, it has been explored in preclinical models as a probe to study appetite regulation, energy balance, and the hypothalamic circuits of food intake. An additional line of research, developed above all by groups studying the cytoprotective effects of secretagogues, has examined in animal models possible actions of GHRP-6 on tissues such as the myocardium and the gastric mucosa, attributed in part to secretagogue receptors present outside the pituitary; these findings remain exploratory in nature.

As for the level of evidence, it is important to be precise. GHRP-6 has a considerably broader and better-characterized body of literature than many obscure research peptides: there are pharmacology studies in animal models and historical early clinical pharmacology data on its ability to induce GH secretion in humans, generated during the decades when secretagogues were being investigated as possible therapeutic agents. However, GHRP-6 was never approved as a drug and its clinical development was largely superseded by later, more selective or orally administered molecules. Therefore, its current status is fundamentally that of a reference compound for research, not that of a product with established therapeutic use. Most of the evidence supporting its cytoprotective and metabolic effects remains in the preclinical realm.

In summary, GHRP-6 is a GH secretagogue hexapeptide that is well defined at the molecular level, with a dual mechanism synergistic with GHRH mediated by the ghrelin receptor GHS-R1a, a distinctive orexigenic profile, and a central historical role in the discovery of the ghrelin pathway. It is offered exclusively as material for scientific research.