Ipamorelin vs MK-677
An evidence-first, side-by-side comparison. We compare what the research supports — not marketing claims.
Last updated
Evidence grade
Animal
Human RCT
What that means
Preclinical evidence from animal models only — not yet shown in humans.
Randomized controlled trials in humans — the strongest evidence we grade.
Status
Research compound
Research compound
Mechanism
Ipamorelin is a synthetic pentapeptide ghrelin mimetic that binds the growth hormone secretagogue receptor (GHSR-1a) and tells the pituitary to release GH. Selectivity is its calling card. Where GHRP-2 and GHRP-6 drag cortisol and ACTH up alongside GH, ipamorelin — in animal studies — lifts GH without significantly moving ACTH or cortisol beyond what GHRH itself does. It also barely touches appetite compared to MK-677, a difference that comes down to how it sits on the receptor. In animal work it usually shares the syringe with a GHRH analog like CJC-1295, the idea being that hitting the GHRH receptor and the GHSR at once amplifies the GH pulse more than either alone.
MK-677 is a non-peptide ghrelin mimetic. It binds the growth hormone secretagogue receptor (GHSR-1a) — the same one the hunger hormone ghrelin hits — and sets off pulsatile GH release from the anterior pituitary, which then raises IGF-1. Where the GHRH analogs (sermorelin, tesamorelin, CJC-1295) act upstream, MK-677 works directly on the GHSR. Two practical consequences follow: it is orally active, so no injections, and it ramps up appetite through that same ghrelin pathway — not what most people chasing body composition are hoping for.
Goals
GH / IGF-1 support, Body composition
Body composition, GH / IGF-1 support
Key risks
- No published human RCTs — all evidence is preclinical; human efficacy and safety are unestablished
- Sold for research use only; purity and dosing accuracy depend entirely on the supplier
- Unknown long-term effects in humans
- Increased fasting glucose and worsened insulin sensitivity — clinically meaningful risk for pre-diabetic or diabetic individuals (Nass 2008 RCT)
- Congestive heart failure safety signal: a phase IIb RCT in hip fracture patients was terminated early due to this finding (Adunsky et al., 2011, PMID 21067829)
- Appetite stimulation via ghrelin pathway; increased body weight reported in RCT (2.7 kg vs. 0.8 kg placebo)
Regulatory
Sold "for research use only" — not approved for human consumption.
Sold "for research use only" — not approved for human consumption.