Quick answer: Ipamorelin (often shortened to “ipa”) is a synthetic pentapeptide, Aib-His-D-2-Nal-D-Phe-Lys-NH2, studied as a growth hormone secretagogue that acts on the ghrelin receptor GHS-R1a. It was described by Novo Nordisk researchers in the late 1990s and is known in the preclinical literature for its selectivity profile. It is a laboratory research compound only. This explainer covers the name, structure, research themes, how it differs from sermorelin and CJC-1295, and what to check on a certificate of analysis.
Where the name Ipamorelin comes from
Ipamorelin is an international nonproprietary-style name rather than a sequence code, and in catalogs it is shortened to “ipa” or written “ipamorelin acetate.” The compound was described by researchers at Novo Nordisk in the late 1990s during work on small synthetic molecules that engage the ghrelin receptor. The “-relin” ending is a family marker: it signals a compound studied for its ability to release growth hormone (GH) in assays, and it places ipamorelin alongside names such as sermorelin and hexarelin.
Structurally it is a pentapeptide, five residues long, with the sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2 and a molecular weight of roughly 712 g/mol. Two features set it apart from natural peptides. First, it contains non-standard building blocks: aminoisobutyric acid (Aib) at the start, and two D-configured aromatic residues. Second, the C-terminus is amidated. Those choices were made to resist peptidases and to keep the molecule compact enough to bind a receptor pocket. The chemistry is summarized in the Ipamorelin research overview.
A growth hormone secretagogue, not a growth hormone
A frequent point of confusion is that ipamorelin is not growth hormone and not a fragment of it. It belongs to the class called growth hormone secretagogues (GHS), meaning compounds that act on the growth hormone secretagogue receptor 1a (GHS-R1a), the same receptor that the natural hormone ghrelin was later shown to activate. Ghrelin was identified in 1999, after synthetic secretagogues had already been studied for years, which is why the early literature talks about an “orphan receptor” before the natural ligand was known.
Ipamorelin is often described as a selective secretagogue. In the original pharmacology paper, cell and animal experiments showed GH release with comparatively little effect on other pituitary axes, namely ACTH and cortisol, when compared with older compounds such as GHRP-6. That selectivity profile is the main reason the name keeps appearing in discussions of the class. It is a statement about assay results in animals and in vitro systems, not a claim about any outcome in people.
It also helps to separate two different families that often share a sentence. GHS-R1a agonists such as ipamorelin act on the ghrelin receptor. Growth hormone-releasing hormone (GHRH) analogs such as sermorelin and CJC-1295 act on a different receptor, the GHRH receptor. The two routes are studied separately and sometimes together. See Sermorelin vs. Ipamorelin and CJC-1295 vs. Ipamorelin for a side-by-side view.
What the preclinical literature examines
Everything in this section is preclinical or mechanistic, drawn from cell, tissue and animal work. None of it is a statement about use in people, and nothing here describes a benefit.
Receptor pharmacology. The foundational paper characterized ipamorelin in rat pituitary cell cultures and in anesthetized and conscious rats and swine, reporting dose-related GH release in those systems and a potency comparable to GHRP-6 with a narrower footprint on ACTH and cortisol readouts.
Skeletal growth models. A follow-up study in young rats examined longitudinal bone growth over several weeks of exposure and measured bone length and related markers. As with most animal endocrine work, the design says more about how the receptor system behaves than about any use outside the laboratory.
Combination questions. Researchers who study the GHRH and ghrelin-receptor routes together have asked whether signaling through both is additive or synergistic in vitro. That question is why the pairing sold as a blend exists as a topic at all; it is discussed in the CJC-1295 and ipamorelin blend explainer.
A caution on interpretation: the primary ipamorelin literature is relatively small, much of it dates from the late 1990s and early 2000s, and many online summaries repeat claims that the original papers never made. Read the primary sources, and be skeptical of any summary that moves from a rat experiment to a statement about people.
Ipamorelin and related compounds at a glance
The table lists descriptors only. It does not rank compounds or imply performance.
| Compound | Class | Length | Receptor |
|---|---|---|---|
| Ipamorelin | Ghrelin-receptor agonist (GHS) | 5 residues | GHS-R1a |
| Hexarelin | Ghrelin-receptor agonist (GHS) | 6 residues | GHS-R1a (also reported at CD36) |
| GHRP-6 | Ghrelin-receptor agonist (GHS) | 6 residues | GHS-R1a |
| Sermorelin | GHRH analog | 29 residues | GHRH receptor |
| CJC-1295 | GHRH analog | 30 residues | GHRH receptor |
The closest sibling in the V8 library is covered in Hexarelin vs. Ipamorelin.
Handling the lyophilized powder
Ipamorelin is supplied as a freeze-dried powder. The general rules for lyophilized peptides apply: keep sealed vials cold, dry and out of light, avoid repeated warming and cooling, and write down the date a vial is first opened. Let a cold vial reach room temperature before the stopper is pierced so that condensation does not form on the cake. The molecule contains histidine and lysine side chains but no cysteine or methionine, so it is not especially prone to the oxidation problems seen with some other peptides; moisture and temperature cycling are the main concerns for long storage.
Because the vial label and the reconstitution record are separate pieces of paper, many labs keep a simple log: lot number, date opened, storage location. General notes on the topic are in the Ipamorelin overview and the broader guide to choosing a peptide supplier.
What to check on an Ipamorelin certificate of analysis
Short synthetic peptides with unnatural residues can carry deletion or racemization by-products, so documentation matters more than a headline percentage.
HPLC purity with the chromatogram. Look for the full trace, not just a single number, and see whether minor peaks are integrated. Understanding HPLC purity explains how to read it.
Identity confirmation. As general buying guidance, ask which method confirms a molecular weight near 712 g/mol and read the result in the report. A method that only repeats the HPLC retention time tells you less than one that reads mass directly.
Lot reference and date that match the vial you are holding, plus the name of the testing laboratory.
Fill amount and whether it describes total powder or net peptide content.
Walk through each section with how to read a COA and Ipamorelin purity testing. For sourcing questions see where to buy Ipamorelin, and for our listing see the Ipamorelin 10 mg product page. Available certificates are published on the COA page.
Common misunderstandings
“Ipamorelin is growth hormone.” It is a small synthetic secretagogue that acts on a receptor. It contains no part of the growth hormone sequence.
“Ipamorelin and CJC-1295 are the same.” They act on different receptors and have separate literatures. The blend on the shop combines two distinct compounds.
“Selective means free of side effects.” Selectivity in an assay describes receptor and hormone readouts in a model. It is not a safety conclusion.
“Animal data predicts human outcomes.” It does not, and this article makes no such claim.
Frequently asked questions
What is Ipamorelin?
A synthetic pentapeptide, Aib-His-D-2-Nal-D-Phe-Lys-NH2, studied as a growth hormone secretagogue that acts on the ghrelin receptor GHS-R1a.
What does the name Ipamorelin mean?
It is a nonproprietary-style name. The “-relin” ending marks compounds studied for growth hormone release; it is not a sequence code.
What is Ipamorelin’s molecular weight?
Roughly 712 g/mol.
Is Ipamorelin the same as growth hormone?
No. It is a small peptide that acts on a receptor and contains no part of the growth hormone sequence.
How is Ipamorelin different from sermorelin?
Ipamorelin acts on the ghrelin receptor GHS-R1a. Sermorelin is a GHRH analog and acts on the GHRH receptor.
Why is Ipamorelin called selective?
In the original animal and cell studies it released GH with comparatively little change in ACTH and cortisol readouts versus older secretagogues. That is an assay finding only.
Is Ipamorelin approved in the United States?
No. V8 Peptides sells it for laboratory research use only, not for human or animal consumption.
What kind of studies mention Ipamorelin?
Cell-culture and rodent or swine pharmacology, plus skeletal growth models in young rats. All preclinical.
What should I look for on an Ipamorelin COA?
An HPLC chromatogram, an identity method that confirms the expected mass, a lot reference matching your vial, a test date and a named laboratory.
How is lyophilized Ipamorelin stored?
Sealed, cold, dry and protected from light, with temperature cycling avoided and the opening date recorded.
All V8 Peptides products are sold for laboratory research use only. They are not drugs, foods, or cosmetics and are not intended for human or animal consumption.
References
- Raun K, et al. Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology. 1998;139(5):552-561.
- Johansen PB, et al. Ipamorelin, a new growth-hormone-releasing peptide, induces longitudinal bone growth in rats. Growth Hormone & IGF Research. 1999;9(2):106-113.
- Kojima M, et al. Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature. 1999;402:656-660.