MK-677 (Ibutamoren): Human Evidence and Safety
An evidence-first MK-677 profile covering ghrelin-receptor activity, human trials, clinical-outcome limits, FDA status, adverse effects, and research quality.
MK-677—also called ibutamoren or MK-0677—is an orally active small-molecule growth-hormone secretagogue and ghrelin-receptor agonist. It is not a peptide, a SARM, or an FDA-approved drug. Human trials show that it can raise growth hormone and insulin-like growth factor 1 (IGF-1), but those biomarker changes have not established a favorable clinical benefit-risk balance for anti-aging, bodybuilding, fracture recovery, obesity, or other promoted uses.
Profile summary
| Field | Current evidence |
|---|---|
| Identity | Non-peptide spiroindoline small molecule; also called ibutamoren or MK-0677 |
| Proposed target | Growth hormone secretagogue receptor 1a, also known as the ghrelin receptor |
| Human evidence | Randomized trials measured GH/IGF-1, body composition, bone-turnover markers, and selected functional outcomes |
| Established clinical benefit | Not established for marketed anti-aging, performance, body-composition, or recovery claims |
| Key safety concerns | Increased appetite, edema/fluid retention, altered glucose metabolism, elevated liver enzymes, and a congestive-heart-failure signal in a hip-fracture trial |
| FDA status | Not approved; FDA states safety and efficacy have not been established |
Identity and mechanism
MK-677 activates the ghrelin receptor and stimulates endogenous growth-hormone release, which can increase circulating IGF-1. Although peptide growth-hormone secretagogues can act at the same receptor, shared receptor activity does not make MK-677 a peptide or make their pharmacokinetics and risks interchangeable.
An increase in GH or IGF-1 is a pharmacodynamic measurement, not by itself a health outcome. Whether a biomarker change helps or harms depends on the population, duration, magnitude of exposure, and endpoints that matter to patients.
What human studies found
GH and IGF-1
A randomized trial in 32 adults aged 64–81 found that short-term MK-677 exposure increased pulsatile GH release and IGF-1. This established target engagement in that population; it did not establish anti-aging, strength, mobility, or longevity benefit.
Body composition and function
In a longer randomized trial of healthy older adults, MK-677 increased GH and IGF-1 and produced a modest increase in fat-free mass. It did not significantly improve strength or function, and the study was not powered to establish long-term clinical outcomes. Reported effects included increased appetite, mild lower-extremity edema, muscle pain, and reduced insulin sensitivity with increased blood glucose.
Bone-turnover markers
Several short randomized studies in older adults reported changes in biochemical markers of bone formation and resorption. Marker movement does not demonstrate fewer fractures, stronger bone, or a favorable long-term skeletal outcome.
Hip-fracture recovery
A multicenter randomized trial in older adults recovering from hip fracture did not improve several functional measures. FDA’s review notes that an ibutamoren hip-fracture trial was terminated early after a potential congestive-heart-failure safety signal. This is especially important because fluid retention and metabolic effects can matter more in medically vulnerable older adults.
What has not been established
Human evidence has not established that MK-677:
- reverses aging or extends life;
- safely builds muscle or improves athletic performance;
- improves sleep in a clinically meaningful, durable way;
- heals injuries or improves recovery after training;
- treats growth-hormone deficiency, osteoporosis, sarcopenia, obesity, Alzheimer’s disease, or hip-fracture recovery; or
- has a safe unsupervised dose, cycle, or combination with peptide secretagogues.
Combining compounds that stimulate the same hormonal axis can increase exposure and uncertainty; a mechanistic rationale is not a safety study.
FDA status and safety
FDA states that ibutamoren is not approved and that its safety and efficacy have not been established. The agency identifies potential effects including increased appetite, water retention, fatigue, muscle pain, altered glucose metabolism and insulin sensitivity, and increased congestive-heart-failure risk in some individuals.
FDA’s compounding safety materials describe serious concerns including hyperglycemia, elevated liver enzymes, edema or fluid overload, and congestive heart failure. The agency also notes limited safety information about prolonged elevation of GH and IGF-1 for the populations in which ibutamoren has been proposed.
Products sold online may add separate risks from incorrect identity, concentration, impurities, degradation, or undeclared active ingredients. “Research use only” language does not establish quality or make personal use safe.
Research-quality checklist
For analytical or laboratory research, verify:
- whether the material is ibutamoren free base, ibutamoren mesylate, or another stated form;
- identity evidence, such as mass spectrometry or NMR, separately from chromatographic purity;
- lot-specific assay, net active content, and counterion correction;
- related substances, residual solvents, water, elemental impurities, and degradation products;
- stability evidence for the exact material and storage condition;
- whether a cited study used the same chemical form, formulation, population, and duration; and
- clinical outcomes separately from GH, IGF-1, or body-composition surrogate endpoints.
The peptide purity-testing guide explains analytical concepts that also apply to non-peptide research compounds. The source directory organizes public documentation signals, and the sourcing policy explains why directory inclusion is not an endorsement. Use the research methodology to interpret evidence grades.
References
- Chapman IM, et al. Stimulation of the GH–IGF-I axis by daily oral administration of MK-677 in healthy elderly subjects. Journal of Clinical Endocrinology & Metabolism. 1996.
- Murphy MG, et al. MK-677 increases markers of bone turnover in healthy and functionally impaired elderly adults. Journal of Bone and Mineral Research. 1999.
- Nass R, et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults. Annals of Internal Medicine. 2008.
- Adunsky A, et al. MK-0677 for patients recovering from hip fracture: a randomized phase IIb study. Archives of Gerontology and Geriatrics. 2011.
- US Food and Drug Administration. Certain bulk drug substances for use in compounding that may present significant safety risks. Updated 2026.
- US Food and Drug Administration. Agebox iKids Growth Day Formula may be harmful due to hidden ibutamoren. 2025.
Bottom line
MK-677 is a non-peptide ghrelin-receptor agonist with demonstrated effects on GH and IGF-1 in humans. Those effects have not translated into an established anti-aging, performance, or recovery treatment, while metabolic, fluid-retention, and heart-failure concerns are clinically important. Evidence summaries should prioritize patient-relevant outcomes and safety signals over hormone changes alone.