Ipamorelin

Ipamorelin is a synthetic pentapeptide growth hormone secretagogue that acts as a selective agonist of the ghrelin receptor (GHS-R1a). It is investigational and not approved for any use.

Last reviewed 2026-10-25 by the PeptideWiki editorial team. Editorial policy.

Overview

Ipamorelin is a small synthetic peptide in the growth hormone releasing peptide (GHRP) family. It was developed in the 1990s by Novo Nordisk researchers as part of a search for secretagogues that release growth hormone from the pituitary without the broad hormonal effects seen with earlier compounds. In its original characterization it was described as the first selective growth hormone secretagogue, because in animal studies it released growth hormone without meaningful increases in ACTH or cortisol at the tested doses.

Ipamorelin was later evaluated clinically for postoperative ileus, a disorder of gut motility after abdominal surgery, reflecting the known effects of ghrelin receptor agonists on gastrointestinal transit. It was not advanced to approval. Today it appears mainly in pharmacology research on the ghrelin receptor and the growth hormone axis. Human data are limited to early clinical studies, and most mechanistic findings come from rodent, swine and in-vitro work.

Compare: Ipamorelin vs CJC-1295, Ipamorelin vs MK-677.

Structure

Ipamorelin is a synthetic pentapeptide with the sequence Aib-His-D-2-Nal-D-Phe-Lys-NH₂, where Aib is α-aminoisobutyric acid and D-2-Nal is 3-(2-naphthyl)-D-alanine. It does not correspond to a natural sequence; it was designed from earlier GHRP scaffolds such as GHRP-6. The unnatural and D-amino acids increase resistance to proteolysis, and the C-terminus is amidated. It is typically supplied as an acetate or trifluoroacetate salt depending on the purification route.

Mechanism

Ipamorelin binds and activates the growth hormone secretagogue receptor type 1a (GHS-R1a), the receptor for the endogenous hormone ghrelin. Activation of this G protein-coupled receptor on pituitary somatotrophs increases intracellular calcium signaling and triggers pulsatile growth hormone release. The response is amplified by endogenous growth hormone releasing hormone (GHRH) and opposed by somatostatin.

In the original animal characterization, ipamorelin's growth hormone response was not accompanied by the ACTH and cortisol elevations reported for GHRP-6 and GHRP-2 at comparable potency, which is the basis for describing it as selective. Ghrelin receptors are also expressed in the gut and enteric nervous system, which provides the rationale for its study as a prokinetic agent.

Research

Growth hormone secretion in animal models

Early pharmacology work in rats and swine showed that ipamorelin produced dose-dependent growth hormone release with a potency comparable to GHRP-6. These studies also reported little effect on ACTH and cortisol, distinguishing it from other GHRPs of the time. Follow-up rodent studies examined longitudinal bone growth and bone mineral content during repeated administration. These findings are from animal models and do not establish clinical effects in people.

Postoperative ileus trials

Because ghrelin receptor agonists accelerate gastrointestinal transit in animals, ipamorelin was taken into clinical development for postoperative ileus after bowel resection. Phase 2 studies were conducted in hospitalized surgical patients. The program did not lead to an approved product, and the available results did not establish a clear benefit over placebo. These trials remain the main source of human safety and pharmacokinetic information for the compound.

Receptor pharmacology tool

In laboratory research, ipamorelin is used as a reference agonist when studying GHS-R1a signaling, receptor selectivity and the interaction between ghrelin receptor agonists and GHRH analogues. Its relatively selective profile in animal work makes it useful for separating growth hormone effects from adrenal axis effects. In-vitro and rodent findings should be interpreted cautiously, because receptor expression and downstream responses differ across species and tissues.

Regulatory status

Ipamorelin is not approved by the FDA for any use and has not been approved by other major regulators. It is not an approved drug product and its status for pharmacy compounding should be checked against current FDA guidance. Growth hormone secretagogues, including ghrelin receptor agonists such as ipamorelin, are prohibited at all times under section S2 of the WADA Prohibited List.

Status changes often. See the regulatory tracker for dated updates.

Quality and identity testing

A certificate of analysis should confirm identity by mass spectrometry, with the observed mass matching the expected mass shown on this page, and report purity by reverse-phase HPLC. Because the sequence contains unnatural residues (Aib, D-2-Nal) and D-amino acids, a good COA or supporting data should address stereochemical integrity, since epimerization or L-isomer impurities can co-elute with the main peak on standard methods. The C-terminal amide should be confirmed, as the free acid differs by about one mass unit and is easy to miss at low resolution. Counter-ion (acetate or TFA) and net peptide content should be stated.

For a walkthrough of each section of a certificate, see how to read a COA.

Storage and stability

Store lyophilized ipamorelin sealed at -20 °C, protected from light and moisture, and allow vials to reach room temperature before opening to limit condensation. The short sequence lacks methionine and cysteine, so oxidation risk is lower than for many peptides, although the tryptophan-like naphthylalanine and histidine residues can still degrade under light and heat. Reconstituted laboratory solutions should be kept refrigerated, used promptly, aliquoted to avoid repeated freeze-thaw cycles, and handled with sterile technique.

Download the Ipamorelin data sheet (PDF): sequence, masses, expected MS ions and handling on one printable page.

Latest research

Frequently asked questions

Related compounds

• GHRP-6

  GHRP-6 is a synthetic hexapeptide that stimulates growth hormone release by activating the ghrelin receptor (GHS-R1a). It was one of the first growth hormone secretagogues and is not approved for any use.

• CJC-1295

  CJC-1295 is a synthetic analogue of growth hormone releasing hormone (GHRH). The name properly refers to a version with a drug affinity complex (DAC) that binds albumin, but is also applied to modified GRF(1-29), which lacks DAC.

• Sermorelin

  Sermorelin is a synthetic peptide consisting of the first 29 amino acids of human growth hormone releasing hormone (GHRH). It was previously FDA-approved as Geref but has been discontinued in the US.

• Tesamorelin

  Tesamorelin is a stabilized synthetic analogue of human growth hormone releasing hormone. It is FDA-approved as Egrifta for reducing excess abdominal fat in adults with HIV-associated lipodystrophy.

References

1. Raun K, Hansen BS, Johansen NL, et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998. Find on PubMed
2. PubMed: all indexed literature on Ipamorelin
3. ClinicalTrials.gov: registered studies mentioning Ipamorelin