Ipamorelin vs PEG-MGF
Ipamorelin (Growth-hormone secretagogue (GHRP) / ghrelin receptor agonist) and PEG-MGF (IGF-1 splice variant analog (PEGylated Mechano Growth Factor)) are documented as co-studied in the PeptiDex library. This page puts the two entries side by side on class, molecular weight, half-life, origin, mechanism and studied research areas — every value taken from the entry it belongs to.
Why these two are co-studied
Cross-referenced for research context — not a usage or combination recommendation.
At a glance
| Attribute | Ipamorelin | PEG-MGF |
|---|---|---|
| Compound class | Growth-hormone secretagogue (GHRP) / ghrelin receptor agonist | IGF-1 splice variant analog (PEGylated Mechano Growth Factor) |
| Research category | Growth & GH-Axis | Growth & GH-Axis |
| Length (amino acids) | 5 amino acids | 24 amino acids |
| Molecular weight | 711.9 g/mol | ~2867 Da (peptide core, excluding PEG) |
| Half-life | ~2 hours (reported approximately 120 minutes) | Extended relative to unmodified MGF due to PEGylation (reported on the order of days), though precise values are not well established |
| Origin | Ipamorelin is a synthetic pentapeptide developed in the 1990s (originally by Novo Nordisk) as a selective growth-hormone secretagogue. It was designed to stimulate GH release with minimal off-target hormonal effects. | PEG-MGF is a PEGylated form of Mechano Growth Factor (MGF), a splice variant of insulin-like growth factor 1 (IGF-1Ec in humans) produced in response to mechanical loading and muscle damage. The MGF peptide corresponds to the unique C-terminal E-domain of this IGF-1 splice variant; PEGylation is added to extend its otherwise very short half-life. |
“Not documented” means the PeptiDex entry records no value for that field. Nothing on this page is estimated, and no figure is carried over from one compound to the other.
How Ipamorelin works
Ipamorelin is an agonist of the growth-hormone secretagogue receptor (GHS-R1a, the ghrelin receptor), mimicking ghrelin to stimulate GH release from the anterior pituitary. It acts on the pituitary and hypothalamus to promote a pulsatile release of growth hormone. Unlike some other GHRPs, it is reported to be highly selective, releasing GH without significantly stimulating ACTH, cortisol, or prolactin at effective doses.
How PEG-MGF works
MGF is a splice variant of IGF-1 whose distinctive C-terminal E-domain is implicated in activating muscle satellite (stem) cells and promoting local muscle repair and hypertrophy after mechanical stress, with actions that appear partly independent of the classical IGF-1 receptor. PEGylation (attachment of polyethylene glycol) protects the peptide from rapid degradation and clearance, substantially extending its half-life compared with native MGF. Much of the mechanistic detail remains at the preclinical/research level.
Mechanistic descriptions reflect published research-literature understanding and are quoted from each compound's own entry. Much peptide research is preclinical (in-vitro or animal-model); mechanism in humans may differ and is not established for many compounds.
Where each one appears in the literature
The research contexts each entry documents. Listing a research area is not a claim of efficacy or a therapeutic indication, and the two lists are not scored against each other.
Ipamorelin
PEG-MGF
What sets each apart
Ipamorelin
Among GHRPs, ipamorelin is noted for its selectivity — stimulating GH release without the appetite, cortisol, and prolactin elevations associated with GHRP-6 and hexarelin.
PEG-MGF
PEG-MGF is based on a mechanically induced IGF-1 splice variant (MGF) rather than mature IGF-1, and PEGylation gives it a long half-life while the peptide's focus is local muscle repair via satellite cells.
Frequently asked questions
What is ipamorelin and what class of compound is it?
Ipamorelin is a synthetic pentapeptide growth hormone secretagogue (a ghrelin/GHS-R1a receptor agonist). It is studied as one of the most selective GHRPs, stimulating pulsatile GH release from the anterior pituitary with minimal effect on cortisol, prolactin, or ACTH in research models.
How does ipamorelin differ from GHRP-2 and GHRP-6?
All three activate the ghrelin receptor (GHS-R1a), but ipamorelin is the most selective: in the research literature it drives GH release without the appetite stimulation seen with GHRP-6 or the cortisol/prolactin elevation associated with GHRP-2. This selectivity is why it is frequently used as a reference GHRP in study design.
Why is ipamorelin commonly studied alongside a GHRH analog like CJC-1295?
Ipamorelin (a GHS-R agonist) and a GHRH analog such as CJC-1295 or sermorelin act on two different receptor pathways. Research protocols pair them because combined GHRH + GHRP stimulation produces a synergistic, amplified GH pulse greater than either compound alone.
What is PEG-MGF?
PEG-MGF is a pegylated form of Mechano Growth Factor (MGF), itself a 24-amino-acid C-terminal splice variant of IGF-1 (IGF-1Ec) produced in response to mechanical stress. Attaching a polyethylene glycol (PEG) group greatly extends its otherwise very short circulating half-life.
How does PEG-MGF differ from regular MGF?
Native MGF has a half-life of only about 5-7 minutes, limiting it to localized action. PEGylation extends the half-life substantially (reported hours to days), so PEG-MGF is studied for systemic subcutaneous administration rather than the site-specific injection unmodified MGF requires.
How does MGF relate to IGF-1?
MGF is an alternative splice variant of the IGF-1 gene (IGF-1Ec) with a unique C-terminal peptide. It is studied for a distinct role in activating muscle satellite cells and tissue repair, separate from the systemic growth signaling of mature IGF-1.
Answers are the ones published on each compound's own PeptiDex entry. They are educational summaries of research-literature context and are not medical advice.