GHRP peptides compared

The short answer

Four compounds, one receptor, and one distinction that matters more than the rest.

GHRP-6, GHRP-2, hexarelin and ipamorelin are all growth hormone-releasing peptides: short synthetic chains that act as agonists at the ghrelin receptor, GHSR-1a. What separates them is not potency so much as selectivity, meaning how much else they do besides acting on growth hormone release. On that axis ipamorelin sits at one end and GHRP-6 at the other.

If you are choosing between them for a research design, selectivity is almost always the deciding property.

One receptor, four different instruments

It is tempting to treat compounds sharing a receptor as variations on a theme, differing only in strength. That is not how this family behaves.

GHRP-6 is the early reference compound and the one with the longest literature behind it. It is particularly associated with effects on appetite signalling, which made it a useful tool for studying that relationship and simultaneously makes it a blunt instrument if appetite is not what you are investigating. Breadth of activity is an asset when it is the thing you are studying and a confounder when it is not.

GHRP-2 is described as more potent at the receptor than GHRP-6, and is also reported to affect other pituitary outputs. Greater potency is sometimes read as straightforwardly better; in an experiment it mostly means the useful concentration range sits lower, and it does nothing to address the attribution problem.

Hexarelin is a hexapeptide studied in comparable contexts at the same receptor. The honest thing to say about it is that it appears less frequently in the published literature than the two numbered GHRPs, so conclusions rest on a thinner base of independent work.

Ipamorelin is the outlier, and deliberately so. It was developed through structural refinement within this family, and the published preclinical work reports growth hormone stimulation at concentrations that did not trigger ACTH or cortisol secretion in the models examined. That is the selectivity the family is otherwise short of. It is also the one member of the four that we supply, and it has its own guide and product page.

Why selectivity decides the experiment

Consider what a non-selective agonist does to your ability to interpret a result. You add the compound, you measure something downstream, and you observe a change. If the compound engages the growth hormone axis and affects the hypothalamic-pituitary-adrenal axis, then the change you measured has at least two candidate explanations and your experiment cannot distinguish between them without additional controls.

A selective compound removes that ambiguity by construction. This is why ipamorelin became the standard tool compound for GHSR-1a work: not because it does more, but because it does less, and what it does is attributable.

The corollary is that selectivity is not universally preferable. If the research question concerns appetite signalling, GHRP-6's breadth is the feature rather than the bug, and the better-characterised compound in that specific context is the right choice. The useful question is never which compound is best but which one isolates the variable you care about.

The GHRH comparison, because it is always confused

A persistent source of confusion is the assumption that GHRPs and GHRH analogues are alternatives. They are not; they act at different receptors.

GHRPs act at the ghrelin receptor, GHSR-1a. GHRH analogues such as CJC-1295 act at the growth hormone-releasing hormone receptor. Both classes are described in the literature as influencing growth hormone release, but they arrive there by separate routes, and the published work describes their combined application as producing a greater response than either class alone in the systems studied. That complementarity, not equivalence, is why the two are studied together, and our guide on CJC-1295 and ipamorelin goes through the pairing.

Reading one class as a substitute for the other is the single most common misconception in this area.

What none of this establishes

Everything above describes observations in defined laboratory and preclinical systems, and depends on the model, the concentration, the exposure time and the method. None of these compounds is an approved medicine in the UK, and none of this constitutes evidence of effects in humans.

Supplying an unlicensed product for human medicinal use is unlawful under the Human Medicines Regulations 2012 regardless of how a listing is worded; our guide on whether peptides are legal in the UK sets out the framework.

Where MY PEPTIDES stands

We stock ipamorelin. We do not stock GHRP-6, GHRP-2 or hexarelin, there are no Certificates of Analysis for them in our library, and this guide is not an offer to supply them.

It is worth being explicit about that mix, because a page covering four compounds from a supplier that sells one of them could easily read as a funnel. The intent here is the opposite: if your protocol calls for GHRP-6, ipamorelin is not a substitute for it and we would rather say so than imply otherwise. Selectivity differences are exactly the sort of thing that makes two compounds in one family non-interchangeable.

The bottom line

GHRP-6, GHRP-2, hexarelin and ipamorelin share a receptor and differ in how much else they do. GHRP-6 carries the broadest documented activity and the longest literature, GHRP-2 is described as more potent, hexarelin has the thinnest evidence base, and ipamorelin is the selective one. Choose on which variable you need isolated, not on potency. We supply ipamorelin and none of the others.

All compounds referenced on this site are discussed strictly in the context of in-vitro laboratory research. Nothing here is a medicine, a supplement or a therapeutic product, nothing here describes administration to humans or animals, and this guide is general information rather than medical, legal or research advice.