Ipamorelin and Hexarelin are supplied strictly as laboratory research materials. They are not approved, intended or authorised for human consumption or any therapeutic use in this context. This article is written for qualified researchers and is not medical advice.
Two ways to hit the same receptor
Ipamorelin and hexarelin belong to the same family — the growth hormone-releasing peptides, or GHRPs — and both work as synthetic ghrelin-mimetics. Each binds the growth hormone secretagogue receptor type 1a (GHS-R1a) on pituitary somatotrophs, activating phospholipase C, mobilising intracellular calcium and driving a discrete, pulsatile release of growth hormone. On that shared mechanism they are near-identical. Where they part company is what else they do at the dose that releases GH. Ipamorelin is the scalpel: highly selective, quiet on the adrenal axis. Hexarelin is the hammer: one of the most potent secretagogues ever characterised, but far less discriminating. This is the classic selectivity-versus-potency trade-off, and it decides which compound belongs in which research design.
| Ipamorelin | Hexarelin | |
|---|---|---|
| Class / peptide type | GHRP — synthetic pentapeptide (5 aa) | GHRP — synthetic hexapeptide (6 aa) |
| Primary target | GHS-R1a (ghrelin receptor) | GHS-R1a + CD36 (scavenger receptor) |
| Structure / MW | Aib-His-D-2Nal-D-Phe-Lys-NH₂ · ~711.9 g/mol | His-D-2MeTrp-Ala-Trp-D-Phe-Lys-NH₂ |
| Selectivity | Very high — little cortisol / ACTH / prolactin | Lower — cortisol / prolactin rise at higher doses |
| Half-life | ~2 hours (IV) | ~70 minutes |
| Main research focus | Clean GH-axis studies; GI motility | Secretagogue potency; cardiac / CD36 biology |
| Regulatory status | Not approved · WADA S2 | Not approved · WADA S2 |
Ipamorelin: the selective benchmark
Ipamorelin (developer code NNC 26-0161) is a synthetic pentapeptide developed by Novo Nordisk in the late 1990s, and it is widely regarded as the first GHS-receptor agonist with a selectivity for GH release comparable to endogenous GHRH. Its compact Aib-His-D-2Nal-D-Phe-Lys-NH₂ sequence produces robust pituitary GH pulses without meaningfully co-stimulating cortisol, ACTH or prolactin — in the landmark Raun et al. work, those hormones stayed indistinguishable from controls even at doses far above the GH-releasing threshold, with FSH, LH and TSH unaffected across the range tested. It also suppresses somatostatin, GH's own inhibitory signal, sharpening the net pulse per dose.
For a researcher, that clean profile is the whole point. When a protocol needs to isolate the GH axis without adrenocortical confounders, ipamorelin is the natural reference reagent. Its short (~2-hour IV) half-life keeps each pulse discrete rather than smearing GH into a sustained elevation. Beyond endocrinology, its receptor is expressed throughout the gut, and ipamorelin has been examined in GI motility and prokinetic research. The full pharmacology sits on our Ipamorelin knowledgebase profile, and research-grade material is available if you need to buy Ipamorelin UK.
Hexarelin: potency and a second receptor
Hexarelin (also called Examorelin) is a synthetic hexapeptide engineered as a metabolically stable analogue of GHRP-6. On a per-mole basis it ranks among the most potent GH secretagogues ever characterised, with human dose-escalation studies documenting powerful GH pulses via subcutaneous and intranasal routes. It reaches GHS-R1a through the same calcium-mediated mechanism as ipamorelin — but it is not nearly as selective. At higher doses some adrenocortical activation appears, and cortisol and prolactin can rise, which limits its usefulness in clean endocrine designs. Research models of the GHRP class also point to more pronounced receptor desensitisation with repeated potent stimulation, a variable worth controlling for.
Hexarelin's distinctive asset is a second target. It binds CD36, a class B scavenger receptor involved in cardiac fatty-acid uptake, independently of GHS-R1a — and it engages GHS-R1a in the myocardium itself. That dual receptor activity has made it a specialist tool for cardiac biology: preclinical ischaemia-reperfusion models report attenuated left-ventricular dysfunction and reduced infarct area through mechanisms that appear separable from systemic GH effects. If your interest is potency or cardiac signalling rather than a spotless endocrine readout, the Hexarelin knowledgebase profile has the detail, and you can buy Hexarelin UK as a research reagent.
What the differences mean in a research context
The table resolves to a single decision: how much off-target activity can your model tolerate? Ipamorelin's selectivity is not a marketing line — it is a measured property that keeps cortisol, prolactin and the gonadotrophins out of the readout, so any downstream change can be attributed to GH itself. That makes it the cleaner instrument whenever the GH axis has to be studied in isolation.
Hexarelin buys greater GH-releasing potency and a genuinely useful second pathway at CD36, but you pay for both. The adrenal and prolactin co-stimulation at higher doses introduces confounders, and its cardiac and scavenger-receptor activity means "hexarelin" is never only a GH tool — it is doing several things at once. For a study probing myocardial GHS-R1a or CD36-mediated signalling that is exactly what you want; for an isolated somatotroph experiment it is noise. Note too that these compounds' half-lives are short and broadly comparable, so duration is rarely the deciding factor — selectivity and receptor breadth are.
Neither is an approved medicine. Both are supplied only as research reagents for in vitro use, both are unapproved by the MHRA and FDA, and both sit on WADA's Prohibited List under S2 (Peptide Hormones). The choice between them is a choice of research instrument, not of therapy.
The bottom line
Ipamorelin and hexarelin start from the same receptor and diverge on philosophy. Ipamorelin is the selective, low-noise benchmark for clean GH-axis work; hexarelin is the more potent, less selective option that also opens a door onto cardiac and CD36 biology. Pick ipamorelin when the experiment demands a quiet endocrine background, and hexarelin when potency or that second receptor is the point. For research-grade material with a COA, see our pages to buy Ipamorelin UK and buy Hexarelin UK, each ≥99% purity.