Overview

Technically a spiropiperidine, not a peptide — but it sits in every peptide catalogue, so it belongs here. It has more human trial data than most peptides on this page, and that data includes the reason it was abandoned.

This is not a peptideIncluded because it is marketed alongside peptides, but is a different class of molecule. Unapproved investigational drug. Not lawful as a dietary supplement in the US. WADA-prohibited.

At a glance

Regulatory status	Not a peptide. Investigational drug; development discontinued. Not approved. Prohibited in sport.
Drug class	Non-peptide, orally active ghrelin receptor agonist — listed here because it is universally marketed alongside peptides
Route	Oral, once daily
Half-life	~4–6 hours (effects persist ~24h)
Evidence rating	3/5 Moderate Evidence rating 3 out of 5: Moderate Small or early-phase human trials, or good controlled topical human data.
Studied in	Multiple phase 2 trials including elderly hip-fracture recovery, sarcopenia, GH deficiency, and a 2-year trial in healthy older adults.

How it works

Orally bioavailable ghrelin receptor agonist producing sustained increases in GH and IGF-1 without injection. The sustained rather than pulsatile elevation is central to both its effects and its problems.

Evidence base

Rated 3 of 5 — Moderate. Small or early-phase human trials, or good controlled topical human data.

Unusually good human evidence for this category — including the negative results that ended development.

Benefits & potential uses

Bars indicate how well each claim is supported: three = strong human evidence, two = moderate, one = preliminary or preclinical.

Reliable IGF-1 elevation, orally Strong evidence

Trials consistently show IGF-1 increases into the young-adult range in older subjects — no injection required.
Increases fat-free mass Strong evidence

A 2-year randomized trial in healthy older adults showed a roughly 1.6 kg increase in fat-free mass versus placebo.
Improved sleep architecture Moderate evidence

Studies show increased slow-wave and REM sleep duration.
Appetite stimulation Moderate evidence

Substantial, and potentially useful in cachexia or during recovery from illness.
Increased bone turnover markers Preliminary

Suggests bone remodelling activity, though fracture-reduction benefit was not demonstrated.

Risks, cons & cautions

Bars indicate seriousness: three = serious or common, two = moderate, one = minor.

Failed its key clinical trial Serious

The hip-fracture recovery program did not meet endpoints, and development was stopped. Fat-free mass gains did not translate into functional benefit.
Congestive heart failure signal Serious

A trial in frail elderly patients was halted after an increase in congestive heart failure cases in the treatment arm. This is the most serious concern with the compound.
Insulin resistance and hyperglycemia Serious

Consistent and dose-dependent; fasting glucose rises and insulin sensitivity falls.
Fluid retention and oedema Moderate evidence

Common, sometimes marked, especially early in use.
Increased appetite and weight gain Moderate evidence

Often unwanted; a substantial fraction of gained weight is not lean tissue.
Lethargy and joint pain Minor

Frequently reported by users at higher doses.
Sold illegally as a supplement Serious

FDA has issued warning letters; it is not a lawful dietary ingredient. Prohibited by WADA.

Who should avoid it

Any heart failure history
Diabetes or prediabetes
Active malignancy
Pregnancy
Tested athletes

If used under medical supervision, monitor

Fasting glucose, HbA1c, insulin
IGF-1
Weight and oedema
Cardiac symptoms

Interactions

Not exhaustive. Always have a pharmacist or physician review your full medication list — including supplements.

Insulin and antidiabetic drugs — MK-677 consistently worsens insulin sensitivity and raises fasting glucose
Corticosteroids — additive metabolic effects
Drugs for heart failure — the compound is associated with a congestive heart failure signal and should be avoided in this population

Regulatory & legal status

Unapproved investigational drug. Not lawful as a dietary supplement in the US. WADA-prohibited.

Infographic

MK-677 (Ibutamoren) — benefits & risks at a glance Download SVG

Where to read further

We link to live literature searches rather than a frozen citation list, so you always see current results — including anything published after our last review.

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Related peptides in Growth Hormone Axis

Terms used on this page

Growth Hormone Secretagogue Receptor (GHS-R1a): GHS-R1a is the G protein-coupled ghrelin receptor mediating growth hormone release and appetite, notable for unusually high constitutive activity in the complete absence of any ligand.
Bioavailability: Bioavailability is the fraction of an administered dose that reaches the systemic circulation chemically unchanged, measured against an intravenous dose of the same drug.
Agonist: An agonist is a ligand that binds a receptor and stabilises its active conformation, producing a biological response rather than merely occupying the binding site.
Insulin-Like Growth Factor 1 (IGF-1): IGF-1 is a 70-amino-acid, proinsulin-like peptide produced mainly by the liver under growth hormone control, and it mediates most of the anabolic effects attributed to growth hormone.
Randomised Controlled Trial (RCT): A randomised controlled trial assigns participants to intervention or control by chance and follows them prospectively, which is what allows an outcome difference to be attributed to the treatment itself.
Lean Mass Loss: Lean mass loss is the fat-free component of weight lost during an energy deficit, encompassing muscle, organ tissue, glycogen and water rather than muscle alone.

This page is educational information, not medical advice. It cannot account for your medical history, medications, or risk factors. Do not start, stop or change any treatment based on it. Speak to a qualified healthcare professional who knows your case.