SOMATOTROPIC RESEARCH

Ipamorelin: Selective Growth Hormone Secretagogue Research Overview

Velox Peptides Research Team·Published June 2026·6 min read
Sequence
Aib-His-D-2-Nal-D-Phe-Lys-NH2
Peptide Class
GH secretagogue (pentapeptide)
Target
Ghrelin receptor (GHS-R1a)
HPLC Purity
≥99% (batch-verified)
For in vitro research use only. Ipamorelin is supplied solely as a research reagent for in vitro use and is not for human or veterinary consumption.

What is Ipamorelin?

Ipamorelin is a lab-made pentapeptide (a short chain of five amino acids) that acts as a selective growth hormone secretagogue — a molecule that prompts the body to release its own growth hormone. In research it switches on the ghrelin receptor (GHS-R1a), the same target as the natural “hunger hormone” ghrelin. It is sold only as a research chemical for in vitro (lab) use, not for use in people or animals.

Its full sequence is Aib-His-D-2-Nal-D-Phe-Lys-NH2. The unusual residues (Aib and several D-form amino acids) make the molecule more resistant to the enzymes that would normally break a peptide down, so it is more stable than the natural peptides it is modelled on.

The key difference from GHRH analogues like CJC-1295 and Tesamorelin is the receptor: those act on the GHRH receptor, while Ipamorelin acts on the separate ghrelin receptor. Because the two pathways are independent, researchers sometimes study them side by side. These are research observations only, not therapeutic effects.

Mechanism: selective GH release

Ipamorelin’s defining feature in the literature is selectivity. Many earlier growth hormone secretagogues also nudged up other pituitary hormones; Ipamorelin was characterised as releasing growth hormone cleanly.

Ghrelin-receptor agonism

Ipamorelin binds the ghrelin receptor (GHS-R1a) on somatotroph cells in the pituitary — a small gland at the base of the brain that makes growth hormone. Activating that receptor prompts those cells to release stored growth hormone in a burst. Because it works one step before growth hormone (prompting the gland rather than supplying the hormone directly), the gland’s own feedback controls remain in the loop in research models.

The selectivity finding

In the original 1998 characterisation, Ipamorelin released growth hormone with potency comparable to GHRP-6, but — unlike GHRP-6 and GHRP-2 — did not significantly raise ACTH or cortisol (stress-axis hormones) at growth-hormone-releasing doses. This clean profile is the basis for the “first selective growth hormone secretagogue” description. These are research observations only.

Relationship to GHRH analogues

Because Ipamorelin (ghrelin receptor) and GHRH analogues (GHRH receptor) act through different pathways, they are studied as complementary tools for probing how the growth-hormone axis is switched on. Duration figures sometimes quoted for Ipamorelin are not well-documented in the primary peer-reviewed literature, so they should be treated cautiously.

Key research findings

The following peer-reviewed studies are representative of the Ipamorelin literature and are summarised for scientific reference only. The evidence base is predominantly preclinical (in vitro and rodent).

Original characterisation & selectivity
Raun K et al. — “Ipamorelin, the first selective growth hormone secretagogue.” European Journal of Endocrinology, 1998

Defined Ipamorelin as a pentapeptide that releases growth hormone potently in vitro and in vivo without significantly elevating ACTH or cortisol above GHRH-control levels — establishing its selective profile.

PMID: 9849822

Preclinical bone model
Svensson J et al. — “The GH secretagogues ipamorelin and GH-releasing peptide-6 increase bone mineral content in adult female rats.” Journal of Endocrinology, 2000

Twelve weeks of continuous administration increased bone mineral content (measured by DXA) in adult female rats, an animal-model readout of sustained GH-axis stimulation.

PMID: 10828840

Glucocorticoid-bone interaction
Andersen NB et al. — “The growth hormone secretagogue ipamorelin counteracts glucocorticoid-induced decrease in bone formation of adult rats.” Growth Hormone & IGF Research, 2001

In glucocorticoid-treated rats, co-administration of Ipamorelin markedly raised the periosteal bone-formation rate compared with glucocorticoid alone — a preclinical observation only.

PMID: 11735244

Gastrointestinal motility model
Venkova K et al. — “Efficacy of ipamorelin, a novel ghrelin mimetic, in a rodent model of postoperative ileus.” Journal of Pharmacology and Experimental Therapeutics, 2009

In a rat post-operative ileus model, repeated dosing accelerated colonic transit and increased food intake — consistent with ghrelin-receptor agonism affecting gut motility, separate from the GH axis.

PMID: 19289567

Ipamorelin and the GHRH analogues

Ipamorelin is often grouped with the GHRH analogues in the somatotropic research category (“somatotropic” just means “to do with growth hormone”), even though it acts on a different receptor. Researchers comparing the ghrelin-receptor and GHRH-receptor routes frequently study it alongside CJC-1295 and Tesamorelin. For the underlying chemistry of the GHRH side, see the CJC-1295 vs Tesamorelin comparison.

Velox Peptides supply information

Velox Peptides supplies Ipamorelin as a lyophilised (freeze-dried) powder, tested by HPLC (a lab method that checks how pure a sample is) with a batch certificate of analysis available on request. To turn the powder back into a liquid for lab work, see the reconstitution calculator. Common storage conventions (keep the sealed powder cold and dry; refrigerate any reconstituted solution and avoid repeated freeze-thaw) are handling guidance, not study-derived specifications. Sold only as a research chemical for in vitro use.

References & further reading

  1. Raun K et al. “Ipamorelin, the first selective growth hormone secretagogue.” Eur J Endocrinol, 1998. PMID: 9849822
  2. Svensson J et al. “The GH secretagogues ipamorelin and GH-releasing peptide-6 increase bone mineral content in adult female rats.” J Endocrinol, 2000. PMID: 10828840
  3. Andersen NB et al. “The growth hormone secretagogue ipamorelin counteracts glucocorticoid-induced decrease in bone formation of adult rats.” Growth Horm IGF Res, 2001. PMID: 11735244
  4. Venkova K et al. “Efficacy of ipamorelin, a novel ghrelin mimetic, in a rodent model of postoperative ileus.” J Pharmacol Exp Ther, 2009. PMID: 19289567

Summaries are paraphrased from the peer-reviewed literature. For full source citations, email support@veloxpeps.com.

Frequently asked questions

Is Ipamorelin a GHRH analogue or a ghrelin-receptor agonist?
It is a ghrelin-receptor (GHS-R1a) agonist, not a GHRH analogue. It acts on the same receptor as the natural hormone ghrelin, a different target from GHRH analogues such as CJC-1295 and Tesamorelin.
How is Ipamorelin different from CJC-1295?
They act on two different receptors: Ipamorelin on the ghrelin receptor (GHS-R1a) and CJC-1295 on the GHRH receptor. Because the pathways are separate, the two are sometimes studied alongside each other for their complementary signals.
Why is Ipamorelin described as “selective”?
In its original 1998 characterisation, Ipamorelin released growth hormone without significantly raising ACTH, cortisol or prolactin — unlike the earlier secretagogues GHRP-2 and GHRP-6. That clean GH-only profile is why it was called the first selective GH secretagogue.
What is the structure of Ipamorelin?
It is a synthetic pentapeptide with the sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2. The Aib residue and D-amino acids improve its metabolic stability versus natural peptides.
What does the research evidence look like?
The published literature is predominantly preclinical — in vitro and rodent studies covering GH release and selectivity, bone mineral content, glucocorticoid-related bone formation, and gastrointestinal transit. Human clinical data in the reviewed literature are limited.
Is Ipamorelin legal to buy in the UK?
Yes — for in vitro research purposes only. It is not a licensed medicine and not for human or veterinary use. Velox Peptides supplies it solely as a research reagent.
Compliance statement. Velox Peptides supplies research reagents for in vitro use by qualified researchers. Every compound is sold strictly as a research reagent. No product is a medicinal product within the meaning of the Human Medicines Regulations 2012. No product has been evaluated by the MHRA or FDA. No product is intended for human or veterinary consumption, diagnosis, treatment, cure, or prevention of any condition. Any use outside lawful scientific research is outside the scope of sale. See our Research Use Policy and MHRA Statement.

All research summaries on this page are derived from publicly available peer-reviewed literature. Velox Peptides makes no therapeutic claims. For research use only.