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MK-677

Ibutamoren, Ibutamoren mesylate, MK-0677

Tier 3 · Limited Human DataNot a peptide
Class
Orally active growth hormone secretagogue
Molecular target
GHS-R1a (ghrelin receptor)
Sequence / structure
Not applicable — small molecule
Evidence tier
Tier 3 — Limited Human Data
Category
Growth Hormone Axis
This is not a peptideA non-peptide small molecule. It is grouped with peptides commercially and sold by the same vendors, but it is a spiropiperidine, not an amino acid chain.

Biology & mechanism

A small-molecule ghrelin receptor agonist that is orally bioavailable — the reason it is grouped with the injectable GHRPs despite sharing none of their chemistry. It raises GH and IGF-1 in a sustained rather than pulsatile fashion, and its long half-life means the elevation persists around the clock.

What the research actually shows

Better human data than most of this category. Merck developed it through multiple trials, including a two-year study in older adults showing sustained IGF-1 elevation and increased lean mass. Development was ultimately abandoned. A trial in hip-fracture rehabilitation was discontinued after congestive heart failure signals.

Regulatory status

Not FDA-approved. Never approved anywhere. Not a lawful dietary supplement — FDA has issued warning letters to companies marketing it as one. Prohibited in sport (WADA S2).

Safety signals

The signals here are concrete rather than theoretical. Trials reported increased fasting glucose and reduced insulin sensitivity, oedema, arthralgia, and an increase in congestive heart failure in one older-adult population. Sustained appetite stimulation is pronounced. The abandoned development programme reflects these findings, not a lack of interest.

No usage guidance is published here

Forge Bioenergy does not publish dosing, reconstitution, or administration protocols for any peptide. See our editorial policy for why. If you are considering any substance on this page, that conversation belongs with a licensed physician.

References & further reading

Regulatory status changes. This page reflects our reading of public sources as of July 2026 and should be independently verified before it is relied upon.

Important notice Forge Bioenergy publishes scientific reference information only. Nothing on this site is medical advice, a therapeutic claim, or a recommendation to use any substance in humans. Many peptides described here are not approved by the FDA for any use, and several are approved only for narrow indications under prescription. We do not publish dosing, administration, or usage protocols. Consult a licensed physician before making any medical decision.