HGH Fragment 176-191 vs Ipamorelin
HGH Fragment 176-191 (Modified GH-fragment peptide) and Ipamorelin (Growth-hormone secretagogue (GHRP) / ghrelin receptor agonist) 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 | HGH Fragment 176-191 | Ipamorelin |
|---|---|---|
| Compound class | Modified GH-fragment peptide | Growth-hormone secretagogue (GHRP) / ghrelin receptor agonist |
| Research category | Metabolic & Mitochondrial | Growth & GH-Axis |
| Length (amino acids) | 15 amino acids | 5 amino acids |
| Molecular weight | ~1817 g/mol | 711.9 g/mol |
| Half-life | ~15-20 minutes (reported) | ~2 hours (reported approximately 120 minutes) |
| Origin | HGH Fragment 176-191 is a synthetic peptide corresponding to the C-terminal region (residues 176-191) of human growth hormone. This portion of the GH molecule was identified as carrying the hormone's lipolytic activity. | 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. |
“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 HGH Fragment 176-191 works
The fragment reproduces the C-terminal, lipolytic-associated region of GH while lacking the domains responsible for GH's growth-promoting and insulin-antagonizing actions. In preclinical models this region has been reported to stimulate fat breakdown (lipolysis) and reduce lipogenesis. It is not intact growth hormone and is not reported to reproduce GH's systemic growth effects.
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.
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.
HGH Fragment 176-191
Ipamorelin
What sets each apart
HGH Fragment 176-191
This is the native GH C-terminal fragment; AOD-9604 is its modified, tyrosine-extended analog. Both isolate lipolytic activity away from full GH signaling.
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.
Frequently asked questions
What is HGH Fragment 176-191?
HGH Fragment 176-191 is a synthetic peptide corresponding to the C-terminal lipolytic region (residues 176-191) of human growth hormone (native sequence LRIVQCRSVEGSCGF). Research identified this segment as carrying the fat-mobilizing activity of GH, while the diabetogenic IGF-1-driving activity resides in a different region (roughly 1-43).
How does HGH Fragment 176-191 differ from AOD-9604?
AOD-9604 is a stabilized analog of HGH Fragment 176-191: it adds an N-terminal tyrosine to the native fragment to improve stability and lipolytic activity. HGH Fragment 176-191 is the unmodified sequence. Both are studied for lipolysis, but the raw fragment is less characterized and has a very short duration.
What does the short half-life imply for research design?
The fragment has a very short half-life (reported ~15-20 minutes), which is why research protocols often describe split dosing (e.g., morning and evening) to maintain exposure. Its rapid clearance is an important consideration when designing pharmacodynamic experiments around lipolysis.
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.
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.