Overview

The most selective of the growth hormone-releasing peptides — it triggers GH release with minimal effect on cortisol, prolactin or appetite. That selectivity is real and is why it displaced GHRP-6 in clinical practice. Efficacy for the outcomes people actually want it for is not established.

Not approved for human use anywhereNo approval anywhere for human use. Sold under research-use labelling. Not FDA-approved. FDA placed several GH-secretagogue peptides under increased compounding scrutiny.

At a glance

Regulatory status	Investigational; phase 2 trials in postoperative ileus were discontinued. Not approved. Common in compounded wellness protocols.
Drug class	Selective ghrelin receptor (GHS-R1a) agonist — pentapeptide
Route	Subcutaneous (research)
Half-life	~2 hours
Evidence rating	2/5 Limited Evidence rating 2 out of 5: Limited Preclinical work plus scattered human reports, uncontrolled use, or negative trials.
Studied in	Phase 2 trials for postoperative ileus (development stopped); animal studies on bone and GH secretion.

How it works

Agonises the ghrelin receptor on pituitary somatotrophs, amplifying GH pulse amplitude and suppressing somatostatin tone. Unlike earlier GHRPs it has little affinity for the pathways that drive ACTH/cortisol and prolactin release.

Evidence base

Rated 2 of 5 — Limited. Preclinical work plus scattered human reports, uncontrolled use, or negative trials.

Human data limited to discontinued phase 2 work in an unrelated indication.

Benefits & potential uses

Bars indicate how well each claim is supported: three = strong human evidence, two = moderate, one = preliminary or preclinical.

Selective GH release Moderate evidence

Clean pharmacology: GH rises without the cortisol and prolactin spikes seen with hexarelin or GHRP-6.
Minimal appetite stimulation Moderate evidence

Unlike GHRP-6, it does not produce the intense hunger that makes those peptides impractical.
Good short-term tolerability Moderate evidence

Trial safety data in the ileus program were reassuring over short exposures.
Synergy with GHRH analogs Moderate evidence

The two mechanisms combine to produce a larger pulse than either alone.

Risks, cons & cautions

Bars indicate seriousness: three = serious or common, two = moderate, one = minor.

No proven clinical benefit Serious

The trials that were run targeted gut motility and were discontinued. Body-composition and recovery claims are untested.
Unapproved and unregulated Serious

Available only through compounding or grey-market suppliers, with corresponding quality uncertainty.
Glucose and insulin effects Moderate evidence

Raising the GH axis can worsen insulin sensitivity over time.
Receptor desensitisation Moderate evidence

Continuous ghrelin-receptor stimulation blunts the response; effects diminish with sustained use.
Head/injection-site reactions Minor

Headache, flushing and local reactions are reported.
Prohibited in sport Minor

WADA-banned.

Who should avoid it

Active malignancy
Pregnancy
Poorly controlled diabetes

If used under medical supervision, monitor

IGF-1
Fasting glucose
Cortisol only if symptomatic

Commonly confused with

These mix-ups cause real harm — two products sold under one name, or two molecules whose effects run in opposite directions.

GHRP-2 Limited Approval Evidence 3/5

Both ghrelin receptor agonists. Ipamorelin is selective and spares cortisol and prolactin; GHRP-2 is more potent at releasing GH but raises both.

Compare side by side

MK-677 (Ibutamoren) Not a Peptide Evidence 3/5

Same receptor, but MK-677 is an oral non-peptide with sustained rather than pulsatile action — and the only one of the two with a long-term human trial, which found a heart failure signal.

Compare side by side

Regulatory & legal status

Not FDA-approved. FDA placed several GH-secretagogue peptides under increased compounding scrutiny.

Infographic

Ipamorelin — benefits & risks at a glance Download SVG

Where to read further

We link to live literature searches rather than a frozen citation list, so you always see current results — including anything published after our last review.

growth hormoneghrelinGHRPcompounded

Related peptides in Growth Hormone Axis

Terms used on this page

Growth Hormone-Releasing Peptide (GHRP): GHRPs are small synthetic peptides that release growth hormone by activating the ghrelin receptor GHS-R1a on pituitary and hypothalamic cells rather than the GHRH receptor.
Receptor Selectivity: Receptor selectivity is the degree to which a ligand acts on its intended receptor rather than related ones, expressed as the ratio between its potency at the target and at each off-target.
Prolactin: Prolactin is a 199-amino-acid anterior pituitary hormone held under tonic dopamine inhibition, central to lactation and the marker of prolactinomas and drug-induced hyperprolactinaemia.
Cortisol: Cortisol is the principal human glucocorticoid, secreted by the adrenal cortex under ACTH control on a pronounced daily rhythm and carried in plasma largely bound to corticosteroid-binding globulin.
Growth Hormone Secretagogue Receptor (GHS-R1a): GHS-R1a is the G protein-coupled ghrelin receptor mediating growth hormone release and appetite, notable for unusually high constitutive activity in the complete absence of any ligand.
Somatostatin: Somatostatin is a cyclic inhibitory peptide, circulating as 14- and 28-residue forms, that suppresses growth hormone release and broadly inhibits endocrine and exocrine secretion.

This page is educational information, not medical advice. It cannot account for your medical history, medications, or risk factors. Do not start, stop or change any treatment based on it. Speak to a qualified healthcare professional who knows your case.