MK-677 (Ibutamoren)
Ibutamoren, MK-0677, L-163,191, Ibutamoren mesylate
The Ground Truth Score
four plain questions, never one numberMK-677 reliably raises GH and IGF-1 in humans. Whether that translates to meaningful clinical benefit is a much messier story.
Bottom line
MK-677 is an orally active ghrelin receptor agonist that has completed multiple human RCTs showing consistent IGF-1 and GH elevation, modest lean mass gains in the elderly, and a safety signal significant enough that Merck abandoned development, including a trial stopped early for congestive heart failure.
Does the science back it?
Do real people feel it?
Is it safe?
Could it be placebo?
"Do real people feel it?" is anecdote, not proof, weighted up because the science is thin, never because it beats a trial. And "could it be placebo?" is not an insult: if you feel better, that's real to you. The point is only to know whether you're paying peptide prices for an expectation.
Why is the evidence this thin? It's mostly economics →
Dose at a glance
full dosing ↓10-25 mg oral once daily, pre-sleep; 25 mg is the standard research dose
Reported, not prescribed. Verify your vial and your math.
The gist
- This is one of the most evidence-backed research compounds in this space. Multiple human RCTs confirm it raises GH and IGF-1 reliably, which is more than most peptides can say.
- The lean mass gains in elderly subjects are real but modest (roughly 1 kg over a year), and no trial has ever shown improvement in strength or function to go with them.
- Merck ran the trials and then walked away. The congestive heart failure signal in the hip fracture study (6.5% vs 1.7% placebo) was the reason. That is not a footnote, that is the headline.
First documented human use
1996. Chapman et al. published oral administration data in healthy elderly subjects in the Journal of Clinical Endocrinology and Metabolism, confirming GH and IGF-1 elevation with daily dosing.
The pitch
What people claim it does
Stated plainly and neutrally, exactly as you'll hear it. I grade each one below.
- Raises GH and IGF-1 to youthful levels without injections
- Preserves or increases lean body mass in aging populations
- Deepens slow-wave sleep and improves recovery
- Supports bone density via increased bone turnover markers
- Potential neuroprotective or cognitive benefit via IGF-1
The data behind each bullet
What actually backs it
Raises IGF-1 and GH to young-adult ranges in older adults
Nass et al. 2008 (2-year RCT, n=65, age 60-81): confirmed GH secretion restored to young-adult levels; fat-free mass increased. Chapman et al. 1996 (PMID 8954023): dose-dependent GH and IGF-1 elevation in healthy elderly subjects. Effect is well-replicated across multiple trials.
Nass et al., Annals of Internal Medicine 2008 (PMID 18981485) ↗Increases lean body mass in elderly or deconditioned patients
Nass 2008 and Adunsky hip fracture trial showed lean mass gains (~1-2 kg over 12-24 weeks), but neither demonstrated functional improvement in strength or mobility. Lean mass increase is real; functional payoff is not established.
Nass et al., Annals of Internal Medicine 2008 (PMID 18981485) ↗Increases bone turnover markers and may support bone density
Murphy et al. (MK-677 Study Group) 1999 (PMID 10404019): 9-week pooled analysis (n=187 elderly adults across three RCTs) showed a 29% increase in serum osteocalcin and 10% increase in bone-specific alkaline phosphatase vs. placebo. Bone density endpoints were not the primary outcome and long-term data is thin.
Murphy et al. (MK-677 Study Group), Journal of Bone and Mineral Research 1999 (PMID 10404019) ↗Slows or reverses Alzheimer's disease progression via IGF-1
Sevigny et al. 2008 (PMID 19015485): 563 patients with mild-to-moderate AD, 12-month RCT. IGF-1 rose 73% at 12 months but there was zero effect on disease progression. Animal data supported the mechanism; human trial refuted the clinical endpoint. Note: the profile previously attributed this paper to 'Mohs et al. 2009' but the lead author is J.J. Sevigny and the publication date is 2008.
Sevigny et al., Neurology 2008 (PMID 19015485) ↗Safe for extended use in wellness or performance contexts
No trial supports long-term safety in healthy adults. Adunsky hip fracture trial was terminated early when 6.5% of MK-677 patients vs 1.7% placebo developed congestive heart failure (a 3.8-fold increase). Across trials: consistent worsening of insulin sensitivity, elevated cortisol, peripheral edema in approximately 40% of subjects, and water retention. Merck discontinued development and the compound has no approved human use anywhere.
OPSS Performance Enhancing Substance Profile: MK-677 ↗Mechanism
How it's assumed to work
Assumed · theoretical pathway
MK-677 is a non-peptide agonist of the ghrelin receptor (GHSR-1a). By mimicking ghrelin, it stimulates the pituitary to release growth hormone in a pulsatile pattern, which then drives hepatic IGF-1 production. Unlike exogenous GH injections, MK-677 preserves the pulsatile nature of secretion rather than producing a flat pharmacological level. This is assumed to be safer than supraphysiologic GH injection, though no long-term comparative human data exists to confirm that assumption. Mechanism is well-characterized in humans. Clinical benefit translation is the open question.
Dosing & handling
What users and clinicians report
10-25 mg orally once daily, typically taken at night before sleep to align with natural GH pulse. 25 mg is the dose used in most clinical trials. Some users report cycling 8-12 weeks on with breaks to manage hunger and water retention. Not injectable.
Reported dose only, never prescribed. The biggest dosing risk is the hunger effect: 25 mg produces significant appetite increase that undermines any body recomposition goal and makes caloric control very difficult. No titration protocol is established. Blood glucose should be monitored. Source purity is unverified for all consumer-market supply.
Timing & food
Typically dosed at night before sleep to leverage the natural GH pulse timing, which may enhance slow-wave sleep effects and reduce daytime hunger. Some users split dose (morning + evening) to manage hunger. Evening dosing is the most common reported pattern.
Half-life
Approximately 24 hours. One of the longest half-lives of any GHS compound, which is why once-daily oral dosing is sufficient and why adverse effects (appetite, water retention, cortisol) persist continuously rather than episodically.
Reconstitution sensitivity
N/A. MK-677 is an oral tablet or capsule, not a reconstituted peptide. No injection or mixing required. Degradation risk is from heat, moisture, and light like any oral compound. Research-chemical supply quality is the primary purity concern.
Real-world signal
What people actually report
Anecdote, not proof, weighted because the science is thin. Here's the record, graded on volume, consistency, and how credible the sources are.
Volume
Very high. MK-677 has one of the largest community footprints of any research compound. Widely discussed on bodybuilding forums and in performance communities for 15+ years.
Consistency
Moderately consistent on the subjective effects (vivid dreams, hunger spike, water retention, improved sleep quality as reported). Inconsistent on lean mass results, which likely reflects the confound of stacking and variable diets.
Source credibility
Mixed to moderate. The anecdotal effects (hunger, water retention, sleep changes) align with the known mechanism. The body recomposition claims are less credible given that trials in controlled settings showed modest lean mass gains without strength improvements.
- Anecdote: extremely strong hunger, especially for carbohydrates, within 1-2 hours of dosing and persisting all day. Users report this is the hardest side effect to manage on a cut.
- Anecdote: vivid, intense dreams reported almost universally. Often the first subjective sign that the compound is active. Consistent with increased slow-wave sleep documented in trials.
- Anecdote: noticeable water retention and puffiness (face and extremities) within the first 1-2 weeks, often mistaken for muscle gain. Most users report it partially resolves after week 3-4.
- Anecdote: joint comfort often improves, especially in users with pre-existing tendon issues. Attributed to IGF-1 effects on connective tissue, though no controlled trial has isolated this outcome.
Placebo risk, Low
MK-677's primary effects (IGF-1 elevation, hunger drive, water retention, vivid dreams) are objective or measurable. IGF-1 rise is verifiable on bloodwork within weeks. Hunger and bloating are hard to fake. Sleep architecture changes (more slow-wave sleep) have been measured in trials. This is one of the few research compounds where the subjective reports are backed by a clear measurable mechanism.
Risk panel
What could go wrong
Adverse events
Documented in RCTs: insulin resistance (consistent across trials, worsens fasting glucose), peripheral edema (approximately 40% of subjects), increased appetite with significant weight gain, elevated cortisol, joint pain, numbness and tingling. Serious: congestive heart failure signal in elderly patients with underlying cardiac vulnerability (6.5% vs 1.7% placebo in Adunsky Phase IIb trial, led to early termination). This CHF rate was 3.8 times placebo and was the primary reason Merck discontinued development.
Theoretical concerns
Sustained IGF-1 elevation raises theoretical concern for tumor promotion. IGF-1 receptor signaling drives cell proliferation; epidemiological data associates chronically elevated IGF-1 with increased risk of breast, prostate, and colorectal cancers. No MK-677 trial was large enough or long enough to assess cancer incidence, so this risk is unquantified not disproven.
Contraindications
Active or history of cancer (IGF-1 elevation is a hard contraindication). Pre-existing insulin resistance or type 2 diabetes (worsens glycemic control). Congestive heart failure or structural heart disease. Children and adolescents (growth plate risk). Pregnancy.
Honest unknowns
Long-term safety beyond 2 years in any population is not established. Cancer risk over multi-year use in healthy adults is completely unknown. The compound has no approved human use anywhere, reflecting the absence of a regulatory safety clearance. Interaction with TRT, exogenous GH, or GLP-1 agonists is not studied. Purity and dosing accuracy of black-market and research-chemical supply is unverified.
Confound watch
Commonly stacked with TRT (testosterone), SARMs, or anabolic steroids, making it impossible to attribute lean mass or recovery improvements to MK-677 alone. Also stacked with GLP-1 agonists (tirzepatide, semaglutide) for body recomposition, where appetite suppression from the GLP-1 offsets MK-677's known hunger drive. Baseline GH deficiency (which increases with age) makes elderly subjects respond more dramatically than young healthy adults, inflating perceived effect size when community reports skew older.
History
Discovery → first use → status
- 1996Chapman et al. published the first human trial showing oral MK-677 stimulates GH and IGF-1 in healthy elderly subjects (Journal of Clinical Endocrinology and Metabolism, PMID 8954023). Merck was the developer.
- 2008Nass et al. published the 2-year RCT in Annals of Internal Medicine (PMID 18981485). Confirmed GH restoration and lean mass gains but failed to show functional improvement. Worsened insulin sensitivity documented.
- 2008Sevigny et al. published the 563-patient Alzheimer's trial in Neurology (PMID 19015485, published November 18, 2008). Despite raising IGF-1 by 73%, MK-677 had no clinical effect on disease progression. Major blow to the cognitive-benefit hypothesis.
- 2011Adunsky et al. Phase IIb hip fracture trial terminated early after 6.5% of MK-677 patients developed congestive heart failure vs 1.7% placebo (a 3.8-fold increase). Merck ultimately did not pursue FDA approval. Compound became a research chemical used off-label.
Verification
The COA standard, applied
Grade adversarially re-reviewed 2026-06-21. Citations corrected 2026-06-22: Chapman 1996 PMID fixed from 9467534 (Murphy 1998 catabolism study) to correct 8954023; Alzheimer trial author corrected from Mohs to Sevigny (J.J. Sevigny et al., published November 2008 not 2009); osteocalcin figure of 29% confirmed against published Murphy 1999 data (29.4%, correctly stated as approximately 29%). Safety risk text expanded to reflect 3.8x CHF rate and Merck program abandonment.
The full verification standard →Sources
Where this comes from
- Nass et al. 2008, Annals of Internal Medicine (PMID 18981485), 2-year RCT, primary evidence anchor ↗· 65 healthy older adults, 2-year double-blind crossover. Confirmed GH/IGF-1 restoration and lean mass gains but no functional improvement and worsened insulin sensitivity.
- Sevigny et al. 2008, Neurology (PMID 19015485), largest single MK-677 RCT (n=563). Lead author is J.J. Sevigny; previously misattributed to Mohs in this file. ↗· Alzheimer's disease trial. Confirmed target engagement (IGF-1 +73%) but zero clinical benefit on disease progression. Showed the mechanism does not reliably translate to clinical endpoints.
- Chapman et al. 1996, Journal of Clinical Endocrinology and Metabolism (PMID 8954023), first GH/IGF-1 human data ↗· Established oral bioavailability and dose-dependent GH secretion in healthy elderly subjects (64-81 years). The foundational human pharmacology paper. Previously mislabeled in this file as PMID 9467534, which is a different study (Murphy et al. 1998, diet-induced catabolism in 8 young adults).
- OPSS (Operation Supplement Safety) MK-677 profile, U.S. military safety resource ↗· Summarizes regulatory status, adverse event profile, and the rationale for why MK-677 is not approved. Useful non-industry reference.
The four lenses reflect the evidence and the real-world record as of the last review and will change as data arrives. Real-world signal and reported feedback are anecdote, not proof. Nothing here is medical advice or a prescription.