Ipamorelin vs ibutamoren (MK-677) side by side: mechanism, half-life, GH pulse pattern, oral vs injectable, and typical cycle length.
Ipamorelin (peptide, injectable) and MK-677 (small molecule, oral) both agonize the ghrelin/GHS-R1a receptor. The choice between them usually comes down to pulse vs sustained elevation, and injection vs oral.
| Ipamorelin | MK-677 | |
|---|---|---|
| Class | Pentapeptide (GHRP) | Non-peptide ghrelin mimetic |
| Route | Injection (SC) | Oral |
| Half-life | ~2 hours | ~24 hours |
| GH pattern | Pulsatile | Sustained 24-hour elevation |
| Cortisol / prolactin | Minimal | Minimal at typical doses |
| Best paired with | GHRH (CJC-1295) | Standalone in most protocols |
Ipamorelin is a pentapeptide growth hormone secretagogue. It is valued in research for its selectivity — stimulating GH release with minimal effect on cortisol or prolactin in published studies.
Selective ghrelin/GHS-R1a receptor agonist that triggers GH release from the anterior pituitary.
MK-677 is technically a small molecule (not a peptide) that mimics ghrelin at the GHS-R1a receptor. Its oral availability and long duration of action have made it a research staple for sustained GH elevation studies.
Non-peptide ghrelin mimetic — selective agonist at GHS-R1a, producing sustained GH and IGF-1 elevation across the dosing interval.
Ipamorelin is the choice when natural pulsatility matters. MK-677 is the choice when oral convenience and round-the-clock IGF-1 elevation matter more.
The table above compares published characteristics, not outcomes for any individual. Mechanism, half-life, and dosing cadence are properties of the molecule; response, tolerability, and suitability are properties of the person. Trial averages describe populations and say nothing definitive about a single case.
All peptide products referenced are intended solely for research, investigational, or licensed professional use. They are not FDA-approved and are not intended to diagnose, treat, cure, or prevent any disease. Consult a licensed medical practitioner before any personal or clinical use.
No. Ipamorelin is a peptide secretagogue that supports endogenous GH release; it is not an anabolic steroid.
Published research shows Ipamorelin is unusually clean on cortisol and prolactin compared to older GHRPs — a major reason it's preferred in modern protocols.
Technically no — it is a small-molecule ghrelin mimetic, but it is commonly grouped with peptides because it targets the same GH pathway.
Yes. Oral availability is one of its main research distinctions versus injectable secretagogues like Ipamorelin.