Ibutamoren is an oral ghrelin mimetic that stimulates growth-hormone secretion. It is a small molecule, not injected growth hormone. A randomized study in healthy older adults examined GH, IGF-1, body composition and physical function. Fat-free mass increased, but strength and function did not improve.[1.1]
Selected human research: 65 adults aged 60–81; randomized, placebo-controlled study. A randomized trial in older adults increased GH, IGF-1 and fat-free mass, without improving strength or physical function. Older adults differ from young trained athletes; appetite, edema and glucose-related effects matter to interpretation. A verified studied dose has not yet been added to this reading note.[2.1]
Studied methods, not dosing advice. Selected evidence, not a complete literature review or formal quality appraisal.
Source scope is listed with each reference. Prepared by PED Evidence with AI assistance. Independent clinician review has not been completed. Review standards
Evidence summarized on PED Evidence
4 completed summaries
4 human-study reports
3 randomized-trial candidates
0 safety-topic reports
These counts describe completed summaries on this site, not the size of the full literature. Publications can share participants; design labels are discovery metadata, not appraisals.
In 65 healthy adults aged 60–81, MK-677 increased fat-free mass but did not improve measured strength or physical function. The main body-composition comparison was at one year within a two-year modified-crossover study.
Nass et al. (2008), one-year results
Outcome
MK-677
Placebo
Fat-free mass
+1.1 kg (95% CI 0.7 to 1.5)
−0.5 kg (95% CI −1.1 to 0.2)
Body weight
+2.7 kg
+0.8 kg
Strength and function
No demonstrated improvement with MK-677
Visceral fat
No significant between-group difference
What dose and schedule were actually studied?
The study used 25 mg orally once daily. It did not compare every-other-day schedules. The participants were older adults, so these findings do not quantify gains in young trained lifters.
What happened to glucose and side effects?
Fasting glucose rose by about 5 mg/dL in the MK-677 group and insulin sensitivity decreased. Appetite increases, mild edema and muscle pain were reported. The sample was too small to settle uncommon or long-term harms.
Abstract-based reading note, checked September 30, 2026. Fat-free mass includes more than skeletal muscle. Studied exposure is not a recommended regimen. Primary trial, PMID 18981485 · Full publication.
A randomized study in healthy older adults examined GH, IGF-1, body composition and physical function. Fat-free mass increased, but strength and function did not improve. [1]
Known half-life
No source-verified value in this profile yet. A treatment schedule or duration of an effect is not a drug half-life.
Half-life describes how quickly the measured drug concentration falls by half. It does not set a dosing interval.
Evidence & important limits
The study reported increased appetite, edema, muscle pain and reduced insulin sensitivity. Its treatment schedule is not a measured drug half-life; that value is not established by this source. [1]
Safety & evidence boundaries
Source-specific information, not a personal safety clearance or monitoring plan.
The study reported increased appetite, edema, muscle pain and reduced insulin sensitivity. Its treatment schedule is not a measured drug half-life; that value is not established by this source.
Interactions, rare harms, long-term effects and reversibility require separate evidence. Do not infer they are absent when the sources here do not address them.
Identity, names & formulations
Canonical compound: Ibutamoren · ibutamoren
Searchable names: MK-677, MK677, MK-0677
Names share a parent research page. Different esters, salts, routes and brands are not assumed to have the same half-life, indication or exposure.
Combination evidence stays attached to the studied combination. It is not automatically assigned to each ingredient.
Understand the evidence types
Read the model and design first, then the population, outcome and limitations. These categories describe evidence, not a best-compound ranking.
Randomized human trials
Compare assigned interventions. Randomization does not by itself establish low bias or relevance to every population.
Controlled human studies
Use a comparison group; allocation and confounding still matter.
Prospective human research
Follows participants forward. It may be observational or interventional, so this is not a separate quality grade.
Observational human research
Describes associations. Confounding can explain differences.
Case reports and series
Useful for unusual events and safety signals, not reliable rates or effect sizes.
Animal research
Can test biology and function in a living model. Human exposure, benefit and safety remain separate questions.
Cell and tissue research
Tests responses in a preparation, including human-derived cells. It is not a human participant trial.
Mechanistic and computational evidence
Helps explain or predict a pathway; predictions need experimental and clinical testing.
Anecdotal reports
Self-reported experiences can generate questions. Product identity, selection bias and other interventions may be uncontrolled.
Systematic reviews synthesize studies and depend on their quality. Preprint status and abstract versus full-paper reading are separate labels. Citation popularity measures attention, not reliability. A study summary is not a formal quality appraisal.
Reference facts checked 2026-09-16. Source scope is listed above; this is not a formal quality appraisal. See each label for full prescribing information.