Peptides
MK-677 (Ibutamoren)
Also called Ibutamoren · MK677 · MK 677 · Nutrobal
MK-677 appeals to people wanting more appetite, better sleep or muscle fullness without injections. It raises growth-hormone-related signals, but extra scale weight or fat-free mass is not the same as stronger muscle, and hunger, fluid retention and glucose changes can work against your goals.
Dosage & duration
Original trial context, not a recommended bulking cycle.
Healthy older-adult randomized trial
Published example · product-specific- Dose
- 25 mg
- How often
- Once daily, oral
- How long
- 12-month main comparison within a two-year study
Adults aged 60–81, with monitoring and dose reductions for some participants; not a safety endorsement for long-term self-use.
Sources: 1
A study lasting a year does not establish that an arbitrary short cycle is safe.
Beyond scale weight
The appetite appeal comes with other changes
What people seek
-
An oral option
More appetite, better sleep and muscle fullness without injections.
What can interfere
-
Fluid and glucose
The older-adult trial found swelling, higher fasting glucose and reduced insulin sensitivity.
Mass and strength In that trial, fat-free mass increased without better strength or function; fat-free mass includes water.
Why it is popular for bulking
It is an oral growth-hormone secretagogue, not a SARM, despite often being sold alongside SARMs. Increased appetite can help someone eat more, but also makes unwanted fat gain easier. Fullness and rapid scale changes are not reliable proof of added muscle.
What the human trial actually improved
In healthy older adults, MK-677 increased fat-free mass but did not improve strength or function. Those participants were not young trained lifters, and fat-free mass includes water as well as muscle.
The trade-offs to keep visible
The trial found reduced insulin sensitivity and higher fasting glucose; appetite, swelling and muscle discomfort were relevant adverse effects. FDA also identifies a heart-failure safety signal from a separate trial in vulnerable patients. Calling it “non-hormonal” or “just a supplement” misses those concerns.
Model details: MK-677 (Ibutamoren) · relative timing
Compare timing and buildup for this compound. The values are not blood concentrations or a measure of strength.
Shows a relative timing scenario; absolute blood concentrations are not calibrated.
Timing assumptions and sources
Historical illustrative assumption. The regulator review found no detailed clinical PK supporting a human plasma half-life. A 24 h GH/IGF effect duration is not a plasma half-life.
One 1 mg input peaks at 1 relative unit after a single dose. Other amounts scale proportionally; overlapping doses add when accumulation is on. Different compounds use separate relative scales.
- Timing half-life used
- 5 hours
- Absorption half-life assumed
- 1.25 hours
- Reference amount for the relative scale
- 1 mg
- Absorption half-life is assumed to be one quarter of the slower timescale (1.25 h); it is not a measured absorption parameter.
- A single 1-unit input has a peak of 1 relative unit; scaling and repeated-dose addition are mathematical assumptions. This normalization is independent of the example dose.
- Do not turn dog bioavailability into human availability.
- No retrieved human paired parent-drug dose, Cmax and Tmax support an absolute scale.
- Future product-specific LUM-201 work may provide calibration; no complete verified candidate was recovered here.
- FDA ibutamoren scientific review presentation, October 2024
Oral availability greater than 60% comes from dogs. Clinical publications describe long action and high oral availability without detailed clinical PK; the review found no additional clinical PK.
- Nass et al. 2008 oral MK-677 older-adult trial
A randomized trial in older adults evaluated oral 25 mg daily and GH/IGF-I/body-composition outcomes. These are not parent ibutamoren plasma-concentration endpoints.
mk-677-relative-timing-2026-10 · version 1
Common questions
Is MK-677 a SARM?
No. Ibutamoren is a growth-hormone secretagogue, even when shops group it with SARMs.
Is fast weight gain all muscle?
No. Fluid retention and increased food intake can both change scale weight; the cited trial did not show better strength.
Sources Labels, studies and notes behind this guide
Catalog evidence: Human clinical trials. This describes the type of evidence, not a clinical review of every claim.
Summary and fact source checks: 2026-10-07. This records source checking, not medical review of the whole page.
Notes on the quick facts
- Why people use it
- Sleep and recovery are also reported goals.
- Main distinction
- It stimulates GH-related pathways.
- Results to separate
- The older-adult trial did not improve strength or function.
- 1. Nass et al. — MK-677 randomized trial
Healthy adults aged 60–81; 25 mg oral daily, initial 12-month comparison in two-year design. Fat-free mass increased without strength/function improvement; glucose/insulin-sensitivity trade-offs.
- 2. FDA ibutamoren safety assessment
Potential congestive-heart-failure signal in a vulnerable hip-fracture population; not a quantified risk for all users.
- 3. FDA ibutamoren scientific review presentation, October 2024
Oral availability greater than 60% comes from dogs. Clinical publications describe long action and high oral availability without detailed clinical PK; the review found no additional clinical PK.
- 4. Nass et al. 2008 oral MK-677 older-adult trial
A randomized trial in older adults evaluated oral 25 mg daily and GH/IGF-I/body-composition outcomes. These are not parent ibutamoren plasma-concentration endpoints.
- 5. Adunsky et al.: ibutamoren after hip fracture
Randomized phase IIb trial; limited functional effects and early termination for a congestive-heart-failure safety signal in this elderly population.
- 6. FDA ibutamoren scientific review, 2024
Regulatory review of proposed uses and safety; no general clinical benefit or approval established by hormone changes.
Keep reading
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