The Compound Report is an educational resource. Nothing on this site constitutes medical advice or encourages personal use of any compound. Always consult a qualified healthcare provider.

Educational reference only. Nothing on this page constitutes medical advice or encourages personal use of this compound. Always consult a qualified healthcare provider before any decision involving your health.

MK-677 / Ibutamoren

MK-677 · Ibutamoren · L-163,191 · MK677

C
Animal replicated
Research chemicalGhrelin Receptor AgonistGrowth Hormone SecretagogueNon-Peptide Small Molecule
RouteOralResearch use only
C
Evidence grade: Animal replicated

Effect demonstrated in multiple animal studies; human data sparse or extrapolated. Grades summarize evidence quality, not whether a compound is appropriate, legal, or risk-free.

At a glance
What it is
Oral non-peptide ghrelin receptor agonist / growth hormone secretagogue; classified outside peptide and SARM categories.
Why people use it
Used primarily for muscle and performance and sleep and recovery.
What the evidence supports
The dose used in all major clinical trials; higher doses increase side effects without clear additional benefit
If you only read one thing

MK-677 has one genuinely compelling advantage over every other compound in the GH secretagogue class: it is oral, once-daily, and well-tolerated enough for months of continuous use. Every other GH secretagogue in this reference requires subcutaneous injection. This convenience advantage is real and pharmacologically meaningful — sustained IGF-1 elevation is well-documented in human trials, the pulsatile mechanism is preserved, and the sleep quality improvement is among the most consistently reported effects in community use. The problem: the compound that reliably raises IGF-1 did not translate this biomarker improvement into the clinical outcomes Merck was trying to demonstrate, and produced consistent glucose metabolism impairment across trial populations. The community uses it for sleep quality, modest body composition benefit, and general GH-axis optimization — applications where the evidence standard is lower than the Merck endpoints and where the benefit-risk calculation may be more favorable than it was in elderly hip fracture patients.

Check interactions →
Published literature
5human RCTs0human studies0animal0in vitro
Evidence reality check
Human evidence
5 human studies
5 randomized; 0 observational.
Preclinical base
0 lab signals
0 animal; 0 in-vitro/mechanistic.
Evidence snapshot
The dose used in all major clinical trials; higher doses increase side effects without clear additional benefit
From the chapter quick-reference block.
Categories
Muscle & PerformanceSleep & Recovery
Properties
Active malignancy: hard stopWADA S2✓ Human RCTNot injectable
Evidence
CAnimal replicated
The Key Human Trial
Nass R, Pezzoli SS, Oliveri MC, et al. (2008). Effects of an Oral Ghrelin Mimetic on Body Composition and Clinical Outcomes in Healthy Older Adults: A Randomized, Controlled Trial. Annals of Internal Medicine. 149(9):601-611. The most rigorous published MK-677 human trial. 25 mg/day vs placebo in healthy older adults. Results: GH and IGF-1 significantly increased; fat-free mass increased +1.1 kg; abdominal visceral fat decreased; fasting glucose increased ~5 mg/dL; insulin sensitivity declined; NO improvement in muscle strength or functional performance. This trial is the primary human evidence base for community use claims and the primary source of safety data for community protocols.
Why Merck Discontinued Development
Merck ran Phase 2 and Phase 3 trials for MK-677 across six indications: GH deficiency, osteoporosis, hip fracture recovery, sarcopenia (muscle wasting in elderly), obesity, and Alzheimer's disease. Two categories of finding ended the program: (1) Biomarker dissociation — IGF-1 rose reliably and fat-free mass increased, but functional clinical endpoints (muscle strength, physical function, hip fracture recovery, cognitive function) consistently failed to improve significantly. Raising IGF-1 did not translate to clinical benefit in the studied populations. (2) Safety signals — consistent glucose perturbation across all trial populations; in the elderly hip fracture trial, an apparent increase in congestive heart failure led to early trial termination. No NDA was submitted. The program was discontinued.
The SARM Misclassification
MK-677 is routinely sold alongside SARMs (RAD-140, LGD-4033, Ostarine) and frequently categorized as a SARM by vendors. It is NOT a SARM. A SARM (Selective Androgen Receptor Modulator) binds and activates the androgen receptor. MK-677 binds the ghrelin receptor (GHSR-1a) — a completely different receptor with no androgen receptor involvement. MK-677 does not suppress testosterone, does not suppress LH or FSH, and does not cause testicular atrophy. The conflation arises from shared gray-market legal status and co-marketing. The pharmacology is entirely different.
The Water Weight Reality
One of the most consistent community complaints about MK-677: significant water retention and weight gain, especially at the beginning of use. Ghrelin receptor agonism drives appetite stimulation (ghrelin is the 'hunger hormone') — users at 25 mg/day typically experience significant increases in appetite that can easily exceed caloric needs. Additionally, GH itself causes sodium retention and water retention. The 'lean mass gain' documented in trials includes intracellular water alongside actual contractile tissue. Community users expecting primarily muscle gains frequently experience primarily scale weight increases from water retention and food intake increases. Managing appetite and caloric intake is essential for meaningful body composition benefit.
Simple view

Need the deep dive?

The default page keeps the decision layer visible first: summary, routes, evidence, and risks. Open the full report for mechanisms, chapter sections, citations, updates, and print/share controls.

Alternatives

Compare nearby options

Browse this classCompare 4 side by side →
CJC-1295 (no-DAC)
C
Same class · Growth Hormone Secretagogue

The Most Common Community GHRH Analog — Sold Under Three Names. The DAC Confusion That Has Been Causing Purchasing Errors for a Decade. Why DAC Changes Everything About the Dosing Protocol. The Four Substitutions That Make Mod GRF 1-29 Last Long Enough to Work. How the GHRH Receptor and GHS-R1a Receptors Synergize. Why Teichman 2006 Actually Studied CJC-1295 WITH DAC — Not This Compound. The Empty Stomach Rule Is Not Optional.

GHRP-2
C
Same class · Growth Hormone Secretagogue

The Most Potent Injectable GHRP. Japan-Approved as a Diagnostic Agent. WADA S2 Banned. The Cortisol Problem That Cuts Against What You're Using It For. The Compound the Community Has Mostly Moved Past — and Why Understanding It Anyway Matters.

Ipamorelin
C
Same class · Growth Hormone Secretagogue

The Compound Defined by What It Doesn’t Do. Every GHRP Before It Elevated Cortisol and Prolactin. Ipamorelin Was Designed to Produce a Clean GH Pulse Without HPA Axis Activation. Raun et al. 1998: 'The First Selective Growth Hormone Secretagogue.' Why the Community Switched From GHRP-6 to Ipamorelin for Most Applications. The GH Stack Partner. The Empty Stomach Rule. Why Selectivity Matters in Practice.

Check interactions