Ipamorelin: The Science of a Selective Growth Hormone Secretagogue
Ipamorelin is one of the most selective growth hormone secretagogues ever characterised, and one of the most searched research peptides in the UK right now. This guide covers what it is, how it works at the receptor level in preclinical research, how it compares to CJC-1295, and what to check before sourcing it for laboratory study.
What ipamorelin is
Ipamorelin is a pentapeptide with the sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2 (CAS 170851-70-4, also designated NNC-26-0161). It was first characterised by Raun and colleagues in 1998, in a study published in the European Journal of Endocrinology, as part of a chemistry programme at Novo Nordisk.
The compound was identified within a series derived from growth hormone-releasing peptide (GHRP)-1. Removing the central Ala-Trp dipeptide from that parent structure produced a shorter molecule that retained strong growth hormone-releasing activity in the assays studied, while gaining a much cleaner selectivity profile. That combination is the reason ipamorelin remains a reference compound in growth hormone secretagogue research.
How ipamorelin works in preclinical research
In the studies that characterised it, ipamorelin acts as an agonist at the growth hormone secretagogue receptor (GHS-R1a), the same receptor targeted by the natural hormone ghrelin and by the earlier GHRPs. In these models, binding this receptor on somatotroph cells in the anterior pituitary is associated with the release of growth hormone.
In the original characterisation, ipamorelin released growth hormone from rat pituitary cells in vitro with potency and efficacy comparable to GHRP-6. Pharmacological profiling using GHRP and GHRH antagonists indicated that it acts through the secretagogue receptor rather than the GHRH receptor.
The defining finding was its selectivity. In the swine models studied, ipamorelin did not alter FSH, LH, prolactin or TSH levels. More notably, and unlike GHRP-6 and GHRP-2, it did not raise ACTH or cortisol in those studies, even at doses far above the threshold needed to release growth hormone in the model. This is what led the authors to describe it as the first selective growth hormone secretagogue, and it is the property most often cited in the research that followed.
Ipamorelin and CJC-1295: two receptors, one axis
Ipamorelin and CJC-1295 are frequently studied alongside each other because, in research models, they act on the same target cell through different receptors. Understanding that distinction is central to the research literature.
CJC-1295 is a growth hormone-releasing hormone (GHRH) analogue, and it acts on the GHRH receptor. Ipamorelin acts on the separate ghrelin, or GHS, receptor. Research into growth hormone secretion has long examined these two inputs as distinct and complementary signals reaching the somatotroph: the GHRH pathway and the secretagogue pathway. Because they engage different receptors, the two compounds are studied for their individual and combined effects on growth hormone release in preclinical models.
For researchers comparing the two pathways, we supply both CJC-1295 with DAC and CJC-1295 no DAC, alongside ipamorelin. Related secretagogues such as GHRP-6, the comparison compound used in the original ipamorelin study, are also available.
Why compound quality matters when sourcing ipamorelin
In peptide research, the identity and purity of the material determine whether results mean anything. A mislabelled or impure compound undermines reproducibility before an experiment begins, and in a five-residue peptide, small synthesis impurities are not always obvious without proper analysis.
Every peptide we supply is HPLC tested by a UKAS and ISO 9001 accredited UK laboratory, and each batch ships with its own Certificate of Analysis. If you want to understand what that data actually shows, our guide on how to read an HPLC chromatogram walks through it.
Purity is only half the picture. Peptides are sensitive to heat and handling, so we store ours at -20°C in medical-grade freezers, with controlled transfer between freezer units to avoid thermal shock. Orders are supplied in Type 1 hydrolytic glass vials and shipped under full cold chain logistics, including thermal packaging and tracked couriers. We cover that process in detail in peptide storage and handling behind the scenes.
Frequently asked questions
What is ipamorelin?
Ipamorelin is a synthetic pentapeptide classified as a growth hormone secretagogue. It is studied in laboratory research for its action on the ghrelin receptor and its effect on growth hormone release in preclinical models.
What receptor does ipamorelin act on?
In research models, it acts as an agonist at the growth hormone secretagogue receptor (GHS-R1a), the same receptor that responds to ghrelin.
What makes ipamorelin selective?
In its original characterisation, ipamorelin stimulated growth hormone release in the models studied without raising ACTH, cortisol, prolactin or the gonadotrophins, even at high doses. That clean profile is why it is described as a selective secretagogue.
How does ipamorelin differ from CJC-1295?
They act on different receptors. CJC-1295 is a GHRH analogue acting on the GHRH receptor, while ipamorelin acts on the ghrelin or GHS receptor. The two are studied as distinct, complementary inputs to growth hormone secretion in research models.
Is ipamorelin legal in the UK?
Ipamorelin is sold strictly as a research-use-only compound, not for human or veterinary use. Our guide on the UK research-use framework explains how this works.
Final thoughts
Ipamorelin remains one of the most characterised selective growth hormone secretagogues available for research, with a documented receptor mechanism in preclinical models and a selectivity profile that still sets the benchmark for the class. If your work calls for it, you can view batch-tested ipamorelin with its Certificate of Analysis on the product page.
Reference: Raun K, Hansen BS, Johansen NL, et al. Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology, 1998, 139(5), 552-561. https://doi.org/10.1530/eje.0.1390552
Updated: 23 Jun 2026
Tide Labs supplies materials strictly for laboratory research use only. Not for human consumption.
