MK-677 (Ibutamoren)
Oral ghrelin-receptor agonist / growth hormone secretagogue
Quick Answer
A small molecule (not technically a peptide, but grouped with the growth-hormone-pathway compounds in this library because it's discussed alongside them) developed originally by Merck as an orally-active alternative to injectable growth-hormone secretagogues.
Why People Are Interested
It's orally active — no injections — which is the main draw compared to injectable secretagogues in this library, combined with real (if ultimately discontinued) pharmaceutical development history rather than being a purely research-only novelty.
What People Hope It May Do
Muscle growth, fat loss, improved sleep, and anti-aging/recovery benefits from sustained GH/IGF-1 elevation without needing injections. (Commonly discussed or proposed — not an established, evidence-backed outcome unless separately stated in Human Evidence above. The trial evidence that exists specifically flagged blood-glucose and fluid-retention risks that this framing tends to omit.)
Potential / Research Areas
Body composition (lean mass, fat mass) in older adults
Recovery from hip fracture and other orthopedic events
Sleep quality
Muscle-wasting conditions
How It May Work
Activates the ghrelin receptor (GHS-R1a) in the pituitary and hypothalamus, stimulating growth hormone and IGF-1 release through a pathway distinct from GHRH analogs like sermorelin or tesamorelin — and, because it's orally bioavailable and long-acting, produces more sustained GH/IGF-1 elevation than short-acting injectable secretagogues.
What Human Research Shows
Studied in randomized, placebo-controlled human trials — including a multi-center Phase 2b study in hip-fracture recovery patients and a 2-year randomized trial in healthy older adults (Nass et al., published in Annals of Internal Medicine, 2008) that reported increased IGF-1 and lean body mass. That older-adult trial is also the source of the safety signal that effectively ended its development: notable increases in fasting blood glucose and insulin resistance markers, and fluid-retention side effects, without the trial demonstrating a clear functional (strength/mobility) benefit large enough to justify those risks. Specific effect sizes need citation verification before publishing — do not state numeric results without pulling them from the primary source.
What Preclinical Research Shows
Extensive preclinical ghrelin-receptor pharmacology from its original development program at Merck (originally as MK-0677) and later Reverse Pharmacology/Aeterna Zentaris.
Six independent readings, not one score. This reflects the volume and stage of research and discussion — it is not a rating of safety or effectiveness.
"Real-World Interest" and "Research Momentum" reflect the volume of public discussion and research activity Element Health Labs has observed — an editorial judgment, not a measured statistic, and not a claim about clinical significance. Anecdotal popularity is not evidence of effectiveness.
What People Report
What Experts Are Saying
Curated commentary specific to MK-677 (Ibutamoren) is planned as the Expert & Creator Library grows. Being listed there does not imply an expert's endorsement of Element Health Labs.
Clinical Trials
For the current, authoritative list of registered trials involving MK-677 (Ibutamoren), search ClinicalTrials.gov directly — trial status changes frequently, and that registry is the source of truth, not a static summary on this page.
Potential Risks & Side Effects
General information only — not individualized guidance. Published trial data flagged fluid retention, increased blood glucose, and insulin-sensitivity changes in older-adult use; because it's not FDA-approved, there is no FDA-reviewed labeling describing contraindications or monitoring requirements for any specific population.
Regulatory Status
Never FDA-approved for any use. MK-677 went through multiple human trials for growth-hormone-deficiency and frailty-related indications but was never submitted for or granted FDA approval; development was effectively discontinued after safety signals (elevated blood glucose/insulin resistance, fluid retention) emerged in older-adult trials without offsetting functional benefit. It is not a controlled substance, but it is also not a dietary supplement ingredient with GRAS status — most sellers market it as "research use only," which describes how it's labeled, not its legal status for human consumption.
What We Still Don't Know
Whether the blood-glucose and insulin-resistance signals seen in the older-adult trial apply broadly across ages and doses being used off-label today, and whether any dose/protocol exists that preserves the GH/IGF-1 benefit without that metabolic tradeoff — the existing trial program was discontinued before that question was answered.
Limitations of Evidence
The most-cited human trials are relatively small, run in narrow populations (older adults, hip-fracture patients), and none demonstrated a functional benefit large enough to support continued development toward approval — a materially different evidence picture than "has been studied in humans" suggests on its own.
Keep Researching
- Search ClinicalTrials.gov for MK-677 (Ibutamoren)
- Expert & Creator Library
- This Week in Peptides
- Understanding Your Bloodwork
- Related peptides:
Last reviewed: 2026-08-17