— Research monograph
Ipamorelin
The pentapeptide secretagogue reported to raise growth hormone without a matching cortisol rise.
- Class
- Synthetic pentapeptide growth hormone secretagogue, Aib-His-D-2-Nal-D-Phe-Lys-NH₂, acting at the ghrelin receptor GHS-R1a
- Half-life (research)
- Reported in the early literature as approximately two hours following intravenous administration in the preclinical work accompanying its characterisation. A validated human figure was not traced to a primary source during preparation of this entry, and none is asserted beyond that. Stated for interpretation of the research literature only.
- Origin
- Described in 1998 by Raun and colleagues at Novo Nordisk, who reported it in the European Journal of Endocrinology under the title that has defined it since: the first selective growth hormone secretagogue.
- Solubility
- Supplied lyophilised, commonly as the acetate salt. Reported as soluble in water and in aqueous buffers. The single lysine and the free imidazole of histidine carry the charge at neutral pH, while the naphthylalanine and phenylalanine contribute substantial local hydrophobicity for a peptide of this length. The C-terminal amide is a structural requirement of the molecule rather than a formality, and the free-acid form is a different compound. No cysteine is present. Physicochemical context only. Merit Sciences publishes no reconstitution or preparation procedures.
What is Ipamorelin?
Ipamorelin is a C-terminally amidated pentapeptide containing two unnatural residues, the α-aminoisobutyric acid at the N-terminus and D-2-naphthylalanine at position three, together with a D-phenylalanine. Those substitutions are what give a five-residue peptide meaningful receptor potency and resistance to rapid proteolysis, and they are the reason it should not be thought of as a fragment of anything endogenous. It is a designed molecule.
The claim to selectivity is the substantive finding and it is worth stating precisely, because it is the property that distinguishes the compound within its class. Raun and colleagues reported that ipamorelin released growth hormone with potency and efficacy comparable to other secretagogues of the period, but did not release adrenocorticotropic hormone or cortisol at levels significantly different from those following growth-hormone-releasing hormone stimulation. Earlier secretagogues in the same class had generally raised cortisol and prolactin alongside growth hormone, and it was that separation, rather than raw potency, that the 1998 paper presented as novel.
The literature on ipamorelin is substantially narrower than for the GHRH analogs it is often co-formulated with, and controlled human trials are limited. Findings described here are from the preclinical and early clinical record and are reported as literature only. Merit Sciences supplies this material strictly for laboratory research use, and publishes no preparation, dosing or administration guidance.
How does Ipamorelin work?
Ipamorelin is described as an agonist at the growth hormone secretagogue receptor 1a, the Gq-coupled receptor for which ghrelin is the endogenous ligand. Receptor activation drives phospholipase C signalling, inositol trisphosphate generation and intracellular calcium mobilisation in pituitary somatotrophs, producing growth hormone release. Because the ghrelin receptor pathway is distinct from the GHRH receptor pathway, the two are frequently studied in combination on the reasoning that they act through separate mechanisms on the same cell, which is the stated rationale for the co-formulations common in research supply. The reported selectivity, releasing growth hormone without a corresponding rise in adrenocorticotropic hormone or cortisol, is attributed in the literature to the specific receptor interaction profile of the pentapeptide rather than to a difference in downstream signalling.
Research applications
- GHS-R1a (ghrelin receptor) pharmacology and agonist selectivity
- Growth hormone secretagogue class comparison studies
- Pituitary somatotroph signalling and calcium mobilisation assays
- Combination studies with GHRH-receptor analogs
- Structure-activity work on unnatural-residue pentapeptides
Form & storage
Ipamorelin ships as a sealed, lyophilized (freeze-dried) powder. Supplied lyophilised, commonly as the acetate salt. Reported as soluble in water and in aqueous buffers. The single lysine and the free imidazole of histidine carry the charge at neutral pH, while the naphthylalanine and phenylalanine contribute substantial local hydrophobicity for a peptide of this length. The C-terminal amide is a structural requirement of the molecule rather than a formality, and the free-acid form is a different compound. No cysteine is present. Physicochemical context only. Merit Sciences publishes no reconstitution or preparation procedures. Store sealed, light-protected, and follow your institution’s handling procedures for research materials.
Frequently asked questions
What is Ipamorelin?
Ipamorelin is a C-terminally amidated pentapeptide containing two unnatural residues, the α-aminoisobutyric acid at the N-terminus and D-2-naphthylalanine at position three, together with a D-phenylalanine. Those substitutions are what give a five-residue peptide meaningful receptor potency and resistance to rapid proteolysis, and they are the reason it should not be thought of as a fragment of anything endogenous. It is a designed molecule. Merit supplies it as a lyophilized research compound for research use only — not for human or veterinary use.
How does Ipamorelin work?
Ipamorelin is described as an agonist at the growth hormone secretagogue receptor 1a, the Gq-coupled receptor for which ghrelin is the endogenous ligand. Receptor activation drives phospholipase C signalling, inositol trisphosphate generation and intracellular calcium mobilisation in pituitary somatotrophs, producing growth hormone release. Because the ghrelin receptor pathway is distinct from the GHRH receptor pathway, the two are frequently studied in combination on the reasoning that they act through separate mechanisms on the same cell, which is the stated rationale for the co-formulations common in research supply. The reported selectivity, releasing growth hormone without a corresponding rise in adrenocorticotropic hormone or cortisol, is attributed in the literature to the specific receptor interaction profile of the pentapeptide rather than to a difference in downstream signalling. Mechanistic descriptions summarize published preclinical findings and are not clinical claims.
What is the half-life of Ipamorelin?
Reported in the early literature as approximately two hours following intravenous administration in the preclinical work accompanying its characterisation. A validated human figure was not traced to a primary source during preparation of this entry, and none is asserted beyond that. Stated for interpretation of the research literature only. Values reflect preclinical or research-context reports, not clinical pharmacokinetics.
Is Merit Ipamorelin for human use?
No. It is sold strictly for research use only — not for human or veterinary use, and not for diagnostic or therapeutic use. Every batch is tested before it is listed, and its certificate of analysis documenting ≥99% HPLC purity is published in the COA library.
References
- Ipamorelin, the first selective growth hormone secretagogue. Raun K, Hansen BS, Johansen NL, Thøgersen H, Madsen K, Ankersen M, Andersen PH. European Journal of Endocrinology, 1998 · PMID 9849822
For research use only. Not for human or veterinary use. Not FDA-approved. Reference information summarized from published literature — not medical or dosing advice.