Comparison
MK-677 vs ipamorelin
Same receptor, opposite shapes. One is an oral small molecule producing sustained elevation; the other is an injected peptide producing a short pulse. Only one of them has a trial that was stopped early.
Both act on the ghrelin receptor, and that is where the similarity ends. MK-677 is not a peptide at all. It is a small molecule taken by mouth with a roughly 24-hour half-life, so it raises growth hormone and IGF-1 continuously. Ipamorelin is an injected peptide producing a pulse measured in hours.
That difference matters more than it sounds. The argument usually made for secretagogues over injected growth hormone is that they preserve the body's natural pulsatile release. Sustained elevation gives that up, which puts MK-677 closer to the thing the class is supposed to be an alternative to.
MK-677 also has considerably more human data, including a trial in older adults with hip fracture that was discontinued after an excess of congestive heart failure in the treatment group. That is the single most important fact on this page.
| Attribute | MK-677 | Ipamorelin |
|---|---|---|
| What it is | Non-peptide small molecule | Five-amino-acid peptide |
| Route | Oral — nothing to reconstitute | Subcutaneous injection |
| Half-life | About 24 hours | About 2 hours |
| GH profile | Sustained elevation | Short pulse, closer to natural secretion |
| Evidence level | Randomised trials in older adults, including a 12-month study | Early pharmacology, no outcome trials |
| Measured outcomes | Increased lean mass without improved strength or function; raised blood glucose | Hormone levels only |
| Serious safety signal | A hip fracture trial was stopped after excess congestive heart failure | None identified, and none looked for |
| Dosing frequency | Once daily | One to three times daily |
Things worth knowing
- MK-677's heart failure signal is the thing to weigh most heavily. Causality is debated, but it emerged in a studied population. That is the kind of finding that only appears when somebody actually runs a trial.
- Ipamorelin having no comparable signal is not reassurance. Nobody has looked.
- Reduced insulin sensitivity and raised blood glucose were consistent findings with MK-677, not occasional ones. That is a poor combination with any glucose-lowering treatment.
- Both increase appetite substantially, because both act on the hunger receptor. This is inseparable from the mechanism rather than a side effect that might be avoided.
- Combining them stacks one mechanism rather than adding another, and compounds the hunger and water retention.
- Both are prohibited at all times in sport. WADA's S2 category names growth hormone secretagogues regardless of chemical class.
Full profile
MK-677
An orally active ghrelin receptor agonist that raises growth hormone and IGF-1. Not a peptide, and not injected. It is a small molecule taken by mouth.
Full profile
Ipamorelin
A selective growth hormone secretagogue that prompts a short pulse of GH release. Widely used, and supported almost entirely by early pharmacology rather than outcome trials.
Related
This page is educational. It describes what published research reports, not what you should do. Peptides discussed here are largely not approved for human use, and nothing on Bioalmanac is medical advice.