GHRP-2 vs Tesamorelin

GHRP-2

GHRP-2, also known by the non-proprietary name pralmorelin, is a synthetic hexapeptide that activates the ghrelin receptor, GHS-R1a. Three of its six residues are D-amino acids, including the non-natural D-2-naphthylalanine, a design feature shared with other synthetic growth hormone-releasing peptides. These compounds were developed by screening for growth hormone release before their receptor had been identified; ghrelin, the receptor's natural ligand, was discovered afterwards. GHRP-2 has been examined in receptor and pituitary cell assays, in animal studies, and in short human endocrine studies that measured hormone secretion. Longer-term human data are sparse, and it is not selective for growth hormone, since rises in other pituitary and adrenal hormones have also been recorded.

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-2 acts

GHRP-2 has been reported to act as an agonist at GHS-R1a, a G protein-coupled receptor present on somatotroph cells of the anterior pituitary and on neurons in the hypothalamus. In somatotrophs the receptor couples mainly to Gq and phospholipase C, and the rise in intracellular calcium that follows triggers growth hormone secretion. This route is separate from that of growth hormone-releasing hormone (GHRH), which acts through its own receptor and cyclic AMP. Part of the response is thought to be hypothalamic, through effects on GHRH neurons and on somatostatin signalling. In human studies, modest increases in ACTH, cortisol and prolactin have been reported alongside growth hormone.

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-2, Growth hormone secretagogue (GHRP); Tesamorelin, GHRH analog (growth hormone secretagogue)
• Length: GHRP-2, 6 amino acids; Tesamorelin, 44 amino acids
• Molecular weight: GHRP-2, 818.0 g/mol; Tesamorelin, 5136 g/mol
• Molecular formula: GHRP-2, C45H55N9O6; Tesamorelin, C221H366N72O67S
• Half-life: GHRP-2, 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.