GHRP-6 vs Tesamorelin

GHRP-6

GHRP-6 is a synthetic hexapeptide, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2, and one of the earliest growth hormone-releasing peptides to be described. It came out of structure-activity work on small synthetic peptides, carried out before anyone knew which receptor they acted on. That receptor, GHS-R1a, was later shown to respond to ghrelin, a hormone made mainly in the stomach, so GHRP-6 is now classed as a ghrelin receptor agonist. It has been used in pituitary cell and receptor assays, in a large body of animal work, and in human endocrine studies of hormone secretion. Because the same receptor takes part in the control of feeding, it has also served as a tool in appetite research.

Tesamorelin

Tesamorelin is a modified form of human growth hormone-releasing hormone (GHRH), keeping all 44 residues but altering the N-terminus. A trans-3-hexenoyl group is attached to the first residue, tyrosine, a change reported to shield the peptide from dipeptidyl peptidase-4, the enzyme that inactivates native GHRH within minutes. That distinguishes it from sermorelin, which keeps only the first 29 residues and carries no protecting group. Human clinical research has concentrated on HIV-associated lipodystrophy, a condition involving abnormal fat distribution, with smaller studies in other areas. Animal and cell work on the growth hormone axis sits alongside this, but outside the lipodystrophy setting, human data are limited.

How GHRP-6 acts

GHRP-6 is reported to bind and activate GHS-R1a, a G protein-coupled receptor that signals mainly through Gq, phospholipase C and intracellular calcium. On pituitary somatotrophs this signalling triggers growth hormone release. The receptor is also expressed in the hypothalamus, including on neuropeptide Y and agouti-related peptide neurons of the arcuate nucleus, which rodent studies have linked to the control of food intake; that distribution is the basis for the peptide's use in feeding research. Small increases in ACTH, cortisol and prolactin have been reported with it in addition to growth hormone. Interactions with somatostatin signalling have been proposed but are less clearly defined.

How Tesamorelin acts

Tesamorelin binds the GHRH receptor on somatotroph cells of the anterior pituitary, the class B G-protein-coupled receptor also targeted by native GHRH and sermorelin. Receptor activation raises cyclic AMP and has been reported to increase both synthesis and release of growth hormone, which keeps a pulsatile pattern because somatostatin and IGF-1 feedback still operate. Circulating growth hormone in turn drives IGF-1 production, mostly in the liver. Studies of adipose tissue have examined the lipolytic action of growth hormone as one link in this pathway, though the separate roles of growth hormone and IGF-1 are not fully resolved.

The records side by side

• Type: GHRP-6, Growth hormone secretagogue (GHRP); Tesamorelin, GHRH analog (growth hormone secretagogue)
• Length: GHRP-6, 6 amino acids; Tesamorelin, 44 amino acids
• Molecular weight: GHRP-6, 873.0 g/mol; Tesamorelin, 5136 g/mol
• Molecular formula: GHRP-6, C46H56N12O6; Tesamorelin, C221H366N72O67S
• Half-life: GHRP-6, not recorded; Tesamorelin, Mean elimination half-life (T1/2) of tesamorelin was 26 and 38 minutes in healthy subjects and HIV-infected patients, respectively, after subcutaneous administration for 14 consecutive days." (original EGRIFTA label, 2010). By contrast t…

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A comparison places two records side by side; it does not merge them. Each description above is drawn from that compound's own record, and the two were not necessarily characterised by the same methods, at the same time, or to the same level of detail. Before comparing any attribute, it is worth establishing that both records describe the substance you think they describe — names are not identifiers, and two entries sharing a name can differ in salt form, stereochemistry or the convention used to state a mass. Where a figure carries no method beside it, the comparison is between two reported numbers rather than between two measurements.