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?
Can you legally get it?
Research-onlyNo legal consumer routeSold labeled 'for research use only, not for human consumption.' There is no approved product, no compounding path, and no one verifying identity, purity, or dose. That label is not a formality, it is the entire legal basis on which it can be sold to you at all.
No FDA-approved product and no 503A compounding route. Sold labeled for research use only, which is the legal basis on which it can be sold at all.
Legal status as of 2026-07-25. This is a separate axis from the grades above, and it does not move them. A vote about who may legally prepare a compound is not evidence that the compound works.
"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. We 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 ↗Prove it
Can you tell if it's working?
The honest test: if it's working, is there any objective way to see it — a blood marker, a scan, a wearable? For a lot of peptides the answer is no, and that's worth knowing before you spend on labs or gear.
Yes — blood IGF-1 confirms it's active and a CGM reliably catches the glucose downside; DEXA fat-free mass is the nearest thing to an efficacy signal but is heavily confounded by water, and no non-blood channel proves a functional benefit.
Bloodwork
A routine lab actually tracks whether this is working.
MK-677 (ibutamoren) is an orally active ghrelin-receptor (GHSR-1a) agonist that amplifies endogenous pulsatile GH release; GH drives hepatic IGF-1 production, so serum IGF-1 — a standard LabCorp/Quest test — rises measurably. The rise reflects the drug's biological action on the GH axis, not merely that the compound is present.
IGF-1 climbs into the upper part of the age-adjusted reference range; in trials daily MK-677 restored older adults' IGF-1 toward the young-adult range within roughly 2-4 weeks. A clear rise above your own pre-dose baseline is the readout.
GHSR-1a agonism amplifies GH pulses, and GH drives hepatic IGF-1 output; IGF-1 is the standard, well-validated blood proxy for GH-axis stimulation in humans, demonstrated specifically for MK-677 in RCTs.
Modest rise above baseline, tracking the IGF-1 increase. Confirmatory only.
IGFBP-3 is GH-dependent and moves with IGF-1, so a concordant rise corroborates GH-axis stimulation; it shifts less dramatically than IGF-1 and is not needed if IGF-1 is drawn.
Draw baseline
Draw IGF-1 before the first dose (single serum IGF-1; time of day is not critical since IGF-1 is stable day-to-day).
Retest
4-8 weeks. IGF-1 often begins rising within 1-2 weeks and plateaus by ~2-4 weeks, so a 4-8 week retest reliably captures the steady-state effect.
Read this before you spend on labs
IGF-1 confirms the GH axis is genuinely stimulated, but it does NOT prove downstream benefit (lean mass, sleep, recovery, appetite) — those can lag or fail to materialize even with a good IGF-1 bump. Separately, order a CMP/fasting glucose (add HbA1c for use beyond ~8-12 weeks): MK-677 reliably raises fasting glucose and lowers insulin sensitivity, so track these as a SAFETY signal, not as evidence it is 'working.' Anyone with insulin resistance or T2D should be cautious.
- Chapman IM et al., J Clin Endocrinol Metab 1996 — daily oral MK-677 restored IGF-1 to the young-adult range in healthy elderly (PMID 8954023) ↗
- Nass R et al., Ann Intern Med 2008 — 2-yr RCT: MK-677 increased GH and IGF-1 to young-adult levels, raised fat-free mass; noted higher fasting glucose / lower insulin sensitivity (PMID 18981485) ↗
Other ways to track it
14-day continuous glucose monitor (Dexcom/Libre) — mean glucose, fasting/morning glucose, and glucose variability/time-in-range; corroborate with a lab HbA1c
A rise in mean and fasting glucose with reduced insulin sensitivity is one of the most RELIABLE objective signals that MK-677 is pharmacologically active — the Nass RCT showed fasting glucose +~5 mg/dL (P=0.015), HbA1c +0.2% (P=0.002), and worsened insulin sensitivity (QUICKI, P<0.001). Frame this honestly: it confirms the drug is working on you, but it is a metabolic DOWNSIDE and safety signal, not a benefit. A CGM turns that abstract risk into a number you can watch and act on.
GH secretagogue-driven GH elevation is counter-regulatory to insulin, reliably raising fasting glucose and reducing insulin sensitivity — a direct, dose-dependent pharmacodynamic effect a CGM measures continuously.
DEXA whole-body scan — fat-free (lean) mass, total fat mass, and visceral adipose tissue (VAT); pair with femoral-neck/spine bone density
A working result shows a real rise in fat-free mass — in the 2-year Nass RCT lean mass rose ~1.6 kg relative to placebo (P<0.001). Honest caveat: a large share of that 'lean' is intracellular water and glycogen (mild edema occurred in ~44% of users), and in the trial strength and physical function did NOT improve, so a DEXA lean-mass bump is not proof of new contractile muscle — this is why it rates as a partial, not direct, efficacy readout. Do NOT expect a VAT drop — unlike tesamorelin, MK-677 did not reduce visceral fat (CT-measured, P=0.68), and total fat mass trended up (P=0.13). Watch bone: femoral-neck density fell slightly versus placebo (P=0.004).
MK-677 is a ghrelin-mimetic GH secretagogue; sustained GH/IGF-1 elevation drives fluid retention and modest lean/fat-free-mass accrual, which DEXA quantifies — but because much of that mass is water and it does not translate to strength, DEXA confirms activity more than benefit. It does not mobilize visceral fat the way GHRH analogs like tesamorelin do.
Home scale (weight trend) + waist circumference + a visual/finger-press edema check on ankles and hands
Expect a fairly quick jump in scale weight — the RCT showed +2.7 kg vs +0.8 kg placebo (P=0.003) — plus possible puffiness/edema and waist increase. Read this honestly: it is largely water retention and appetite-driven intake, NOT muscle, and is easily mistaken for muscle gain. Its value is as a cheap corroborator: rapid weight-up with edema confirms the drug is acting, and pairs with DEXA to separate water from tissue. A stalling or falling weight during a bulk suggests under-dosing or non-response.
GH-secretagogue fluid retention plus the strong ghrelin-driven appetite (especially for carbohydrates) reliably add body water and intake, producing prompt, objective weight and girth changes that a scale and tape capture.
Oura or WHOOP — deep (slow-wave) sleep minutes and REM minutes, tracked with a multi-week baseline
Some users may see an uptick in deep-sleep and/or REM minutes; a polysomnography study (Copinschi 1997) found increased slow-wave and REM sleep. Be honest about the weakness: that human evidence is short-term lab PSG, longer-term benefit is unestablished, and consumer wearables estimate sleep stages imperfectly with high night-to-night noise — so a null or noisy result does NOT mean the compound is inactive. Vivid dreams are near-universal anecdotally but are subjective and not a wearable metric.
GH secretion is physiologically coupled to slow-wave sleep, and ghrelin-mimetic GH secretagogues appear to reinforce that coupling, plausibly increasing deep-sleep and REM time.
Bottom line
MK-677 is easy to confirm as pharmacologically active but hard to validate as beneficial. Blood IGF-1 (handled separately) and a CGM glucose rise are the most reliable objective confirmations it is 'doing something'; a DEXA lean-mass gain and prompt scale-weight/water gain corroborate activity but are heavily confounded by water. The clean efficacy wins seen with other compounds are absent here: no visceral-fat reduction (unlike tesamorelin), no proven strength or functional improvement, a slight bone-density dip, and only weak, noisy wearable-sleep support. The strongest signals (IGF-1, higher glucose, appetite, water weight) are as much side-effect as benefit — so track it, but interpret any positive DEXA or weight change conservatively, because none of these readouts proves a durable clinical benefit.
Logging baseline vs retest is the whole game. The Truth Tracker is our free log for bloodwork, DEXA, genetics, and wearable data — bring your own numbers.
How to track it →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.