MK-677 (Ibutamoren)

Clinical Summary

MK-677 (ibutamoren mesylate) is a non-peptide, orally active growth hormone secretagogue that mimics ghrelin at the GHS-R1a receptor. Developed by Merck in the 1990s for GH deficiency, sarcopenia, osteoporosis, and age-related frailty. Reached Phase II/III trials but was never FDA-approved. Now being developed as LUM-201 by Lumos Pharma for pediatric GHD (Phase 3 recruiting, NCT06948214).

Who benefits most (theoretical): Elderly with somatopause, sarcopenia, osteopenia, or poor sleep. Individuals who want GH-axis stimulation without injections.

The honest reality: MK-677 has a genuinely strong evidence base — 19 human studies including multiple RCTs, a landmark 2-year trial, and ~1,500 total human exposures. It reliably raises GH and IGF-1 to youthful levels via physiological pulsatile release. However, Merck abandoned it because clinical outcomes (functional improvement, fracture reduction, AD progression) did not match the biomarker improvements. The GH/IGF-1 increase is real; whether that translates to meaningful clinical benefit in healthy individuals is unproven. Safety concerns about insulin resistance and CHF are serious and well-documented.

Why not approved: Phase II/III trials failed to show clinically meaningful functional improvement. The hip fracture trial (PMID: 21067829) was stopped early due to CHF signal (6.5% vs 1.7% placebo). The Alzheimer's trial (PMID: 19015485) showed no effect on AD progression despite 12 months of treatment. Insulin resistance was consistent across all trials.

The surrogate endpoint lesson: MK-677 is a textbook case of the surrogate endpoint trap — the biomarker (GH/IGF-1) moved perfectly, the patients didn't get better. This pattern (biomarker success + clinical failure) echoes vitamin E, beta-carotene, and HRT history.

Indications & Evidence

Reading this table: Stars = evidence volume. Type = what kind of evidence (see legend). BH = Bradford Hill causal strength (/9). Safety = FAERS/trial signals for THIS specific indication. One row = one decision.

Hard rule: Star rating cannot exceed the causal taxonomy ceiling for its Type. E.g., Type=UCC caps at 3/5 regardless of how many studies exist from one lab.

Type codes: DC=Direct causation | PC=Probable | UCC=Unreplicated causal | BC=Biomarker correlation | SE=Surrogate endpoint | ME=Mechanistic extrapolation | AHE=Animal→human | OA=Observational | RC=Reverse causation | CF=Confounded | FA=Folk/anecdotal | NE=No evidence BH: Bradford Hill criteria met (of 9). 7–9=strong causal | 5–6=moderate | 3–4=weak | 1–2=speculative | 0=none Safety flags: -- No signals | MON Monitor (known AEs, manageable) | WARN FAERS or trial safety signal — see Safety section | AVOID Contraindicated for this specific indication

Star rating legend: 5/5 Multiple large RCTs + meta-analyses | 4/5 Several human RCTs | 3/5 Some human pilot/moderate clinical data | 2/5 Limited/conflicting | 1/5 No evidence or negative results

Key rating changes from Mode 5 classification:

• Reversal of diet-induced catabolism: 4/5 → 3/5 (UCC ceiling — single study, N=8, no independent replication)
• Bone turnover markers: 4/5 → 3/5 (BC ceiling — markers ≠ fracture reduction)
• BMD increase: 3/5 → 2/5 (SE ceiling — surrogate endpoint, no fracture data)
• Hip fracture recovery: 2/5 → 1/5 (trial was definitively negative + safety signal)

Prescribing

Dosing

Bedtime dosing rationale: MK-677 amplifies the natural nocturnal GH pulse. Bedtime aligns drug effect with physiological GH secretion peak, reduces daytime appetite/lethargy, and leverages the sleep-improving effects.

Cycle considerations: No standard cycling protocol in clinical literature. The 2-year Nass trial showed sustained efficacy without tachyphylaxis. Community protocols suggest 8–12 week cycles with 4-week breaks to manage insulin sensitivity, but this is not evidence-based. A Korean rat study (PMID: 30450851) showed somatostatin upregulation with prolonged use abolished the GH response by 6 weeks — relevance to humans is unclear since human trials show sustained IGF-1 elevation.

Formulations

Route: Oral only — key advantage over injectable peptides.

Product quality risk: MK-677 is sold exclusively through unregulated research chemical suppliers. A 5-year multi-country surveillance study (PMID: 40551438) found ibutamoren was the #1 most frequently detected molecule among seized SARM/GHS supplements, with some products containing undisclosed hormones (testosterone, estradiol, GH). No pharmaceutical-grade product exists for human use.

Safety

Adverse Effects (from clinical trials)

Interactions

Contraindications

Absolute:

• Active malignancy — elevated GH/IGF-1 promotes tumor growth; IGF-1 is mitogenic and anti-apoptotic
• Congestive heart failure (any class) — hip fracture trial showed 3.8x CHF rate vs placebo (PMID: 21067829)
• Diabetic retinopathy — IGF-1 promotes retinal neovascularization
• Pregnancy & lactation — zero safety data

Relative (use with extreme caution):

• Type 2 diabetes or prediabetes (HbA1c > 5.7%) — MK-677 worsens insulin resistance
• History of cancer within 5 years — theoretical risk from elevated IGF-1
• Family history of strong cancer predisposition (BRCA, Lynch, etc.) — elevated IGF-1 concern
• Cardiac risk factors (HTN, LVH, coronary disease) — fluid retention + CHF signal
• Renal impairment — fluid retention risk; unclear renal clearance
• Hepatic impairment — CYP3A4 metabolism; case report of hepatotoxicity (PMID: 40675653)
• Pediatric (<18) — limited data; theoretical premature growth plate effects
• Carpal tunnel syndrome — GH/IGF-1 exacerbates CTS

FAERS Signal Table (from BioMCP)

Reading FAERS data: Only ~11 total reports exist for ibutamoren — extremely low volume for a compound widely used through gray markets. All signals are unreliable at this N. Two clusters emerge: hepatic (liver injury + jaundice + DILI + cholestasis = 6 events) aligning with PMID 40675653, and cardiovascular (CVA + ACS + DVT + PE = 6 events) aligning with the CHF signal from clinical trials. 4 new reports filed since 2024-01-01 (DILI, CVA+syncope, psychosis, abnormal behaviour). Searching "MK-677" returned zero FAERS results — only "ibutamoren" is indexed. Low report volume reflects: (a) not FDA-approved, no prescriber base; (b) gray-market use with no reporting infrastructure; (c) polypharmacy confounders in most reports.

Monitoring

Stop immediately if: persistent edema, dyspnea, orthopnea (CHF signs), fasting glucose >7.0 mmol/L or HbA1c >6.5%, rapid weight gain >3 kg in a week (fluid), new or worsening carpal tunnel symptoms.

Synergies & Stacking

Common stack concepts: Anti-aging (MK-677 + Sermorelin), Sleep optimization (MK-677 + Melatonin + Magnesium), Bone health (MK-677 + Vitamin D3 + Calcium), Insulin resistance mitigation (MK-677 + Berberine/Metformin), Recovery (MK-677 + BPC-157 + TB-500), Prolactin management (MK-677 + P5P), GH amplification (MK-677 + CJC-1295)

Individual Response Modifiers

Sex-Specific Considerations

Genetic Modifiers

Community & Anecdotal Evidence

Disclaimer: This section captures real-world user reports from online communities. None of this constitutes clinical evidence. N-sizes are approximate. Selection bias, placebo effect, and recall bias are inherent. Presented for completeness, not as medical guidance.

Dominant Sentiment

Mixed-positive across ~500+ Reddit threads + forum discussions. Users generally favorable; medical community more skeptical. Sleep improvement is the strongest consensus across all sources.

What Users Report

Community Dosing vs Clinical

Popular Stacks (Community)

Red Flags & Skepticism Notes

• MLM involvement: None detected for MK-677 specifically.
• Influencer concentration: More Plates More Dates is the dominant voice (generally balanced). No single influencer driving disproportionate hype. Multiple "SARM review" channels are overwhelmingly positive with vendor affiliations — low credibility.
• Astroturfing signals: YES — repetitive positive language across "review" sites. Phrases like "best bang for the buck" and "poor man's HGH" appear verbatim across dozens of seemingly independent sites.
• Commercial bias: HIGH — the vast majority of "MK-677 review" websites earn commission on vendor links. Content is systematically biased positive.
• Product counterfeiting: HIGH — widespread bunk product reports. Only ~52% of "SARMs" products contain what they claim (JAMA). Some products contain undisclosed compounds (documented: one product contained undisclosed testosterone, estradiol, and GH alongside MK-677; PMID: 39145153).
• Government pushback (2025): DEA/ONDCP "Get Smart About Drugs" and "Just Think Twice" programs published anti-MK-677 articles emphasizing cancer risk and CHF signals, signaling increased regulatory attention.

Folk vs Clinical Reality Check

Community experience strongly aligns with clinical data on sleep improvement — this is the single most consistent community signal and matches the Copinschi study (PMID: 9349662) perfectly. Appetite increase and water retention are also reported at frequencies matching clinical trial incidence. Where community diverges from clinical data: users report more skin/hair benefits than any clinical study has measured (no clinical data exists on these endpoints — they may be real GH/IGF-1 effects that were never studied, or placebo/expectation bias). Community muscle gain expectations ("5–15 lbs") far exceed clinical findings (~1–3 kg FFM, much of it water/glycogen). Community fat loss claims are directly contradicted by clinical evidence.

Reactive hypoglycemia clarification (from MPMD/community): MK-677 raises blood sugar → pancreas overshoots with insulin → secondary hypoglycemic dip. This is NOT true hypoglycemia — it's a rebound phenomenon. Important mechanistic distinction underappreciated in community discussions.

Emerging concern — chronic GHSR agonism and neurological risk: More Plates More Dates coverage of theoretical brain damage from chronic ghrelin receptor agonism (based on animal models of chronic ghrelin exposure) is generating community discussion. No human data exists, but the concern is mechanistically plausible given GHSR expression in hippocampus and the pro-inflammatory macrophage programming finding (PMID: 38092245).

Deep Dive: Mechanisms & Research

GHS-R1a Receptor Biology

The growth hormone secretagogue receptor (GHS-R1a) is a 7-transmembrane GPCR expressed in:

• Anterior pituitary (somatotrophs) — primary site for GH release
• Hypothalamus (arcuate nucleus, VMH) — appetite regulation, energy homeostasis
• Hippocampus — memory, neurogenesis (PMID: 34755494)
• Cardiovascular system — cardiac myocytes, vascular endothelium (PMID: 10790589)
• Peripheral tissues — liver, pancreas, GI tract (PMID: 11061542)
• Macrophages — GHSR promotes pro-inflammatory M1 polarization via PKA-CREB-IRS2-AKT2 pathway (PMID: 38092245)

GHS-R1a has ~50% constitutive activity — it signals even without ligand binding. MK-677 further activates this already-active receptor.

Structural biology (PMID: 34737341): Liu et al. (2021) cryo-EM structure at 3.3 Å resolution. Ibutamoren binds the orthosteric pocket between TM3/TM5/TM6/TM7, partially overlapping ghrelin but engaging distinct hydrophobic interactions. Enables rational design of next-generation GHS-R1a agonists.

Pharmacokinetics

Key distinction: Plasma half-life (~4–6h) is much shorter than biological effect (~24h) because MK-677 triggers GH pulses persisting after drug clearance. Enables once-daily dosing.

Why Merck Abandoned MK-677

1. Hip fracture CHF signal (2011) — 6.5% vs 1.7% CHF rate; trial stopped early
2. Alzheimer's failure (2008) — Largest trial (N=563), zero cognitive benefit despite robust IGF-1 increase
3. Insulin resistance — Consistent across all trials; unacceptable for chronic elderly use
4. Functional outcomes never matched biomarkers — GH/IGF-1 reliably increased, but strength, function, and clinical endpoints did not
5. Patent expiration — Without positive Phase III, no commercial path

New Mechanisms (2024–2026)

Anti-cancer activity via MDM2-p53 pathway (PMID: 39668330): In vitro study (Turkish group, 2025) found ibutamoren binds the p53-binding pocket of MDM2, reducing viability of cancer cell lines with functional MDM2-p53 but not in mutant lines. Entirely novel mechanism unrelated to GH/IGF-1 axis. Preliminary — requires independent replication.

GHSR in macrophage programming (PMID: 38092245): Myeloid-specific GHSR knockout mice showed attenuated systemic inflammation and insulin resistance on HFD. GHSR promotes pro-inflammatory macrophage polarization. Implication: chronic GHSR agonism (as with daily MK-677) could theoretically worsen obesity-associated inflammation. Mouse data only.

Stress-appetite neurobiology (PMID: 41260416): Japanese study (Hoshi University, 2026) used MK-677 as a tool compound. MK-677 reversed stress-suppressed feeding via PVN neuronal pathways distinct from anxiolytics. Confirms central nervous system activity beyond simple appetite stimulation.

Next-generation GHSR agonists (PMID: 40091212): Chinese group (Genescience Pharma, 2025) developed capromorelin derivatives with EC50 = 0.49 nM — 100-fold more potent than ibutamoren. Oral bioavailability 43.6% in dogs. MK-677 may become obsolete as a research tool.

Intranasal MK-677 fails to engage brain ghrelin system (PMID: 39813130): Gothenburg study (2025) tested intranasal delivery of ghrelin, GHRP-6, and MK-677 in mice. Only GHRP-6 increased food intake intranasally; MK-677 failed to engage brain ghrelin signaling via this route. Confirms oral administration is MK-677's viable route — intranasal is not an alternative.

GHSR-1a activation renoprotective in diabetic kidney disease (PMID: 41951014): Silibinin activates GHSR-1a to protect against diabetic kidney disease via mitophagy (2026). Not MK-677 directly but establishes GHSR-1a agonism as potentially renoprotective — a novel indication pathway for the receptor.

Novel GHSR agonist improves cardiomyocyte contractility (PMID: 41206722): AC01, a novel GHSR agonist, improves cardiac contractility via Gαi without Ca²⁺ mobilization (2026). Suggests GHSR agonism may have cardiac applications distinct from MK-677's known CHF risk — possibly dependent on biased agonism at the receptor.

Ghrelin-based interventions in Parkinson's (PMID: 41643910): Systematic review (2026) of ghrelin system interventions in Parkinson's disease models. GHSR agonism shows neuroprotective potential in animal models. MK-677 likely included as a representative compound. No human Parkinson's trials for MK-677.

The IGF-1 and Cancer Question

Epidemiological studies link elevated IGF-1 to increased risk of colorectal, prostate, breast, and lung cancer (PMID: 15562834, 14559892). Mechanism: IGF-1 promotes cell proliferation and inhibits apoptosis via PI3K/Akt/mTOR.

However: No MK-677 trial (~630 patients, up to 2 years) reported increased cancer incidence. The theoretical risk remains but direct evidence does not exist. Duration and sample sizes may be insufficient. The MDM2-p53 finding (PMID: 39668330) adds an unexpected wrinkle — in vitro anti-cancer activity via a non-IGF-1 mechanism — but is far too preliminary to change the risk calculus.

Prudent approach: Avoid in anyone with active cancer, recent cancer history, or strong cancer predisposition genetics.

Clinical Trials (from BioMCP / ClinicalTrials.gov)

Regulatory Status (from BioMCP)

• FDA: Not approved. Products sold as supplements are "adulterated" per FDA. Listed as ingredient posing significant safety risks. FDA Orphan Drug Designation (#579617) for pediatric GHD under Lumos Pharma. FDA issued recall of "iKids-Growth" products containing undeclared ibutamoren (March 2026).
• EMA: Not approved. No data.
• WADA: Prohibited S2 (growth hormone secretagogues). Banned at all times. Detectable in hair (PMID: 40882886) and urine.
• DEA: Not scheduled. Legal to purchase as "research chemical" labeled "not for human consumption."
• SARMs Control Act: Proposed legislation would schedule MK-677 alongside SARMs; not yet enacted as of 2026.
• Australia (TGA): Schedule 4 (prescription only); no approved product; enforcement actions taken.
• EU: Variable — most countries classify as unapproved medicinal product.
• Regulatory context: MK-677 was abandoned by Merck for commercial reasons (failed primary endpoints in late-phase trials, patent expiration, unacceptable metabolic side effects for chronic use). Revived by Lumos Pharma as LUM-201 specifically for pediatric GHD using a predictive enrichment marker (PEM) strategy. #1 most seized GHS globally per GEON 5-year surveillance (PMID: 40551438).

Ataraxia Verdict (as of 2026-04-14)

Evidence Classification (Mode 5: Evidence Classifier)

Synthesized view in Indications & Evidence table above (Type + BH + Safety columns). Detailed rationale for each classification below.

Hype Check (Mode 1: Fallacy Radar)

Overblown claims:

• "MK-677 is a SARM" — FALSE. It is a ghrelin mimetic / GH secretagogue. Does not bind androgen receptors. Commonly mislabeled due to being sold alongside SARMs.
• "MK-677 builds muscle like steroids" — FALSE. FFM gains are modest (~1–3 kg over months), largely water/glycogen, with no strength improvements in RCTs.
• "MK-677 burns fat" — FALSE. No fat loss in any trial. Increases appetite significantly, may cause weight gain.
• "No side effects" — FALSE. Insulin resistance, edema, appetite increase, and a CHF signal are well-documented.
• "Anti-aging miracle" — UNPROVEN. Restores youthful GH/IGF-1 levels, but the 2-year Nass trial showed this did NOT translate to functional improvement. Classic surrogate endpoint trap.
• "As effective as HGH injections" — FALSE. Most experienced users acknowledge substantially less potent.

Legitimate strengths:

• One of the best-studied compounds in the "research chemical" space — 19 human studies, ~1,500 total exposures
• Reliably raises GH/IGF-1 via physiological pulsatile mechanism (not continuous)
• Oral administration — major practical advantage over injectables
• Sleep improvement is genuinely interesting, replicated across two age groups
• Anti-catabolic effect during caloric restriction is well-demonstrated (small N)
• Bone turnover activation is real (clinical significance uncertain)

Key fallacies detected:

1. Surrogate endpoint conflation — the biggest error. "IGF-1 goes up, therefore you're younger." This is exactly the pattern that failed with vitamin E, beta-carotene, and HRT.
2. Cherry-picking — community heavily promotes sleep and body composition data while ignoring the hip fracture CHF signal and Alzheimer's failure.
3. Survivorship bias — "millions use it safely" ignores non-reporters and those with adverse effects.
4. Appeal to authority — Smith & Thorner (original developers) remain optimistic despite negative late-phase trials; potential career confirmation bias.

Evidence Gaps

• No dose-response study below 25 mg in adults (10 mg barely studied)
• No intermittent dosing protocol study (community uses cycles, no evidence)
• No long-term (>2 yr) cancer surveillance data
• No study combining MK-677 + metformin to mitigate insulin resistance
• No sleep study beyond initial weeks (tolerance question)
• No study on skin, hair, or nail effects (strong community signal with zero clinical data)
• Hepatotoxicity prevalence unknown (1 case report)
• No reproductive/fertility effects data
• NAFLD/NASH trial (NCT05364684) completed Dec 2024 — results unpublished
• Fibromyalgia trial (NCT00116129) completed 2008 — results unpublished
• Whether CHF signal (6.5% vs 1.7% in frail elderly) applies to healthier populations
• Prolactin elevation prevalence and clinical significance (community reports ~10–15%; only transient elevation documented in PMID: 8768828)
• Whether the emerging 12.5 mg "5 on / 2 off" community protocol has any advantage over continuous 25 mg

Bias Flags (Mode 4: First Principles)

What evidence survives scrutiny? The pharmacodynamic data is bulletproof — MK-677 raises GH and IGF-1 in every study. Sleep improvement is replicated (but single lab). Anti-catabolic effect is real but small-N. Body composition changes are modest and may be partly water. ALL clinical endpoint trials failed.

What mechanisms have clinical translation? GH/IGF-1 elevation: YES (pharmacologically active). Sleep improvement: YES (replicated). Bone density: PARTIAL (delayed, less potent than bisphosphonates). Functional improvement: NO. Cognitive improvement: NO. Fracture prevention: NO.

What dosing is evidence-based? Only 25 mg/d from human RCTs. Everything else (10 mg, 12.5 mg, cycling) is extrapolation or community convention.

Who benefits from this compound being popular? Research chemical vendors (thin margins but high volume). YouTube fitness channels. Underground bodybuilding ecosystem. Nobody benefits significantly from it being unpopular — Merck abandoned it, no competitor exists. This is relatively clean economics compared to branded supplements.

Manipulation Flags (Mode 2: Manipulation Shield)

• Industry marketing: LOW for MK-677 specifically — no major supplement brand pushes it. Marketing is underground/gray-market. However, research chemical vendor sites use pseudo-scientific language and cherry-picked study summaries.
• Influencer economics: MODERATE — YouTube fitness/biohacker channels monetize MK-677 content with affiliate links to research chemical vendors. More Plates More Dates is the dominant voice (generally balanced). Many smaller channels are systematically positive with undisclosed vendor relationships.
• Counter-narrative manipulation: LOW — no one profits from fearmongering against MK-677 (no competing patented GHS on market). The safety concerns come from Merck's own trials (high credibility) and emergency medicine case reports (moderate credibility). This makes the safety data MORE credible, not less.
• Cui bono summary: Research chemical vendors win if you take it (but margins are thin, ~$30–80/month). Nobody wins if you don't. Merck neither gains nor loses from its current status. Lumos Pharma benefits if it succeeds in pediatric GHD (separate formulation, separate market). The economics are cleaner than most supplements.
• Red team highlight: The single most concerning angle is chronic IGF-1 elevation and cancer risk. No MK-677 trial was long enough or large enough to detect cancer signals. The epidemiological data linking IGF-1 to cancer is strong. Users taking MK-677 for years are running an uncontrolled experiment with their cancer risk.

Decision Support (Mode 3: Clarity Compass)

• Health utility score: 4/10 — strong pharmacodynamic GH/IGF-1 elevation but weak clinical outcome evidence in healthy adults; metabolic monitoring burden (glucose, HbA1c, IGF-1, HOMA-IR) and cancer-risk uncertainty cap utility. Higher utility only in documented somatopause or specific sleep/body-composition clinical contexts under supervision.
• Opportunity cost: Adding MK-677 means: blood glucose monitoring, HbA1c tracking, IGF-1 monitoring, potential insulin resistance management, edema risk, cost ($30–80/month), and ongoing cancer risk uncertainty. High monitoring burden for unproven benefit.
• Hell Yes or No (Sivers test): No. Evidence for clinical benefit in healthy adults is weak despite strong pharmacodynamics.
• Regret minimization: In 5 years, unlikely to regret NOT taking MK-677. May regret starting it if metabolic side effects or cancer risk materializes.
• Verdict: WATCH LIST — genuinely interesting compound with real pharmacological effects, but clinical benefit in healthy adults is unproven and metabolic risks are real.
• Conditions for upgrade to CONDITIONAL: (a) New low-dose studies showing benefit with manageable metabolic profile, or (b) specific clinical need arises (documented somatopause with low IGF-1, severe sleep issues unresponsive to other interventions), or (c) NAFLD trial results show hepatic benefit, or (d) LUM-201 Phase 3 succeeds and provides better dosing guidance.

Bottom Line

MK-677 is pharmacologically effective — it does exactly what it claims (raises GH/IGF-1 via ghrelin mimicry with preserved pulsatility). The problem is that raising GH/IGF-1 did not produce the clinical benefits researchers hoped for, while the metabolic side effects (insulin resistance, CHF risk) are real and consistent. It is one of the most honest disappointments in endocrine pharmacology: the biomarker moved, the patients didn't get better.

The sleep effects are the most interesting signal worth following — strong community consensus aligning with replicated (but single-lab) clinical data. For most people, the risk-benefit ratio is unfavorable. The compound is being actively replaced by next-generation GHS-R1a agonists with 100x greater potency.

Evidence quality: MODERATE — multiple RCTs, but negative primary outcomes in late-phase trials; strong pharmacodynamic data, weak clinical efficacy data; zero meta-analyses.

Practical Notes

• Legal status: Not a controlled substance in US. Sold as "research chemical — not for human consumption." Proposed SARMs Control Act would schedule it alongside SARMs. #1 most seized GHS globally (PMID: 40551438).
• WADA: Prohibited under S2 at all times. Detectable in hair for months (PMID: 40882886) and urine.
• Storage: Room temperature, sealed container, protect from moisture. Oral form — no reconstitution needed.
• If someone insists on using: Start at 10 mg/day (not 25 mg), take at bedtime for sleep benefit, monitor fasting glucose weekly for first month, get baseline and follow-up IGF-1 and HbA1c. Stop if fasting glucose >110 mg/dL or HbA1c rises above 5.7%. Do NOT use if pre-diabetic, diabetic, or metabolically unhealthy. Consider berberine or metformin to mitigate insulin resistance (pharmacological reasoning, no direct evidence). Source from suppliers with third-party COA testing — product counterfeiting is endemic.
• Cost: $30–80/month from research chemical suppliers. Quality highly variable — no pharmaceutical-grade product exists. FDA has issued recalls for products with undisclosed ingredients.
• Bunk product test (community): If no hunger increase and no sleep change within 7 days at 25 mg, product is likely counterfeit.

What We Don't Know

• Long-term cancer risk from chronic IGF-1 elevation (epidemiologically plausible, no MK-677-specific data)
• Whether lower doses (5–10 mg) retain benefits with acceptable metabolic risk
• Whether intermittent dosing (e.g., 5 on/2 off) mitigates insulin resistance
• Hepatotoxicity prevalence beyond the single 2025 case report (PMID: 40675653)
• Effects on fertility and reproductive hormones with chronic use
• Whether sleep quality benefits persist long-term or develop tolerance
• Interaction with aging — does the benefit/risk ratio shift with age?
• Product purity and consistency from research chemical suppliers
• Whether the CHF signal (6.5% vs 1.7% in hip fracture trial) applies to healthier populations
• Whether the MDM2-p53 anti-cancer mechanism (PMID: 39668330) has any in vivo relevance
• NAFLD/NASH trial results (NCT05364684 completed Dec 2024, unpublished)
• Fibromyalgia trial results (NCT00116129 completed 2008, unpublished)
• Whether GHSR-mediated pro-inflammatory macrophage programming (PMID: 38092245) is clinically relevant in humans
• Whether somatostatin upregulation causes desensitization with long-term use in humans (shown in rats, PMID: 30450851)
• Neurological consequences of chronic GHSR agonism — community concern gaining traction, based on animal chronic ghrelin exposure models; no human data
• Whether GHSR-1a agonism is renoprotective in humans (PMID: 41951014 — animal data only)
• Whether biased GHSR agonism (e.g., Gαi-selective as in PMID: 41206722) could achieve cardiac benefit without CHF risk
• Prevalence and clinical significance of prolactin-related side effects (~10–15% community-reported)
• Whether GHSR rs490683 polymorphism (PMID: 40347908) predicts differential MK-677 response
• Neuroprotective potential in Parkinson's disease (PMID: 41643910 — systematic review of animal models only)

References

Systematic Reviews & Key Reviews

Landmark RCTs

Mechanism & Pharmacology Studies

Additional Human Data

Safety & Case Reports

Regulatory & Anti-Doping

Epidemiological (IGF-1 / Cancer)

Pharmacogenomic & Receptor Biology