Ibutamoren

Ibutamoren is an unapproved oral ghrelin-receptor agonist that raises endogenous GH and IGF-1. Older-adult trials found a lean-mass signal without a reliable strength or function benefit.

tier D · growth hormone · +1.1 kg year-one fat-free-mass change in one older-adult trial

verdict

Oral MK-677 increased GH, IGF-1, and fat-free mass in selected older adults, but strength and most function measures did not improve. The record does not establish athletic, recovery, anti-aging, or longevity benefit.

the core tension

Ibutamoren reliably moves GH and IGF-1 and can move fat-free mass. The human record does not show that those changes produce stronger, more functional, or longer-lived people, and it contains material glucose, fluid, and heart-failure concerns.

what it is

Ibutamoren, also called MK-677, MK-0677, or LUM-201 in later development, is a small-molecule ghrelin or growth-hormone-secretagogue receptor agonist. The free base and mesylate salt are distinct identity records.

what it does

It increases pulsatile endogenous GH secretion and circulating IGF-1. That endocrine effect can change fat-free mass, but it does not turn a DXA or biomarker result into strength, mobility, or recovery.

origin

There is no FDA-approved ibutamoren product or prescribing label. FDA has identified ibutamoren as an unapproved hidden ingredient and flagged potential safety concerns when ibutamoren mesylate is used in compounding.

does it work

The clearest human result is a modest fat-free-mass increase in healthy adults aged 60 to 81, paired with more weight and worse glucose handling but no strength or function improvement. Hip-fracture rehabilitation findings were mixed and the trial stopped early for safety.

key facts

• molecular formula: C27H36N4O5S (free base); C27H36N4O5S·CH4O3S (mesylate record)
• molecular weight: 528.6657 g/mol free base; 624.7725 g/mol mesylate
• amino acids: n/a (small molecule, not a peptide)
• half-life: not stated; no qualifying public base PK set in the cited pivotal human reports
• type: small-molecule ghrelin and growth-hormone-secretagogue receptor agonist
• CAS: 159634-47-6 free base; 159752-10-0 mesylate
• 71 randomized healthy older adults in the publication
• +1.1 kg fat-free-mass change over year one
• 123 randomized hip-fracture patients in the publication

frequently asked questions

Is ibutamoren FDA approved?

No. FDA describes ibutamoren as unapproved, and no FDA prescribing label exists for it.

Does more fat-free mass mean more strength?

No. In the healthy older-adult trial, fat-free mass increased but strength and function did not. Fat-free mass also includes water-related components.

Did it improve hip-fracture recovery?

The trial produced one gait-score signal amid largely negative function testing and stopped early after a congestive-heart-failure signal. That is not reliable rehabilitation evidence.

What is its human half-life?

This page does not publish one. The required public trials do not provide a complete concentration-time PK set, so no vendor, patent, review, or animal number is substituted.

Are ibutamoren and ibutamoren mesylate the same specification?

No. They are related free-base and salt records with different formula, molecular weight, CAS, and UNII values. A retail product name does not establish either identity or trial equivalence.

related peptides

• sermorelin: The ibutamoren evidence cited on this page does not establish outcomes, mechanism, approval, or identity for sermorelin.
• Mecasermin: The ibutamoren evidence cited on this page does not establish mecasermin's indication, mechanism, approval, or outcomes.

reptides grades the research record and cites the literature behind every call. research reference only; not medical advice.