MK-677 (Ibutamoren): An Oral Non-Peptide Ghrelin Receptor Agonist for Growth Hormone Release

This content is provided by Superpower Health for educational and informational purposes only. MK-677 (ibutamoren) is not FDA-approved for any indication and is not available through Superpower or by prescription. Merck's clinical development program was discontinued; MK-677 is currently distributed as a research chemical through unregulated gray-market channels. This page is not a substitute for medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.

Most compounds in the growth hormone secretagogue category are peptides: chains of amino acids that must be injected because they would be degraded by the digestive tract before reaching the bloodstream. MK-677 is the exception. It produces the same core pharmacological effect as peptide GH secretagogues (stimulating pulsatile GH release and raising IGF-1), yet it does so as a small-molecule spiropiperidine that survives oral administration and remains active for roughly 24 hours. That combination attracted serious pharmaceutical attention in the 1990s and drove an extensive Merck clinical program spanning hip fracture, age-related muscle loss, and Alzheimer's disease. That program was ultimately discontinued, and the reasons why are as instructive as the positive findings that preceded them.

Here is what MK-677 is, how it works at the receptor level, what Merck's trials found and did not find, and why understanding its safety signals matters for anyone evaluating this compound in its current form.

Key Takeaways

• Regulatory Status: As of April 2026, MK-677 is not FDA-approved for any indication. Merck's investigational new drug program was discontinued following pivotal trial results; no NDA was submitted.
• Research Stage: Phase 2 and Phase 3 clinical trial data published; development discontinued. Not in any active regulatory pipeline.
• Availability: Not available by prescription. Distributed through unregulated gray-market channels as a "research chemical." The FDA has not authorized any manufacturing, sale, or distribution for human use.
• Prescribing information: No FDA prescribing information exists. See PubChem CID 9939050 for compound reference data.
• How it works: Binds the ghrelin receptor (GHSR-1a) as an agonist, stimulating pulsatile GH secretion and sustained IGF-1 elevation via oral administration.
• What trials showed: Merck's trials confirmed GH and IGF-1 restoration in healthy elderly adults, with increased fat-free mass but no improvement in functional strength or outcomes. Safety signals included elevated fasting glucose, increased HbA1c, and congestive heart failure events in an elderly hip fracture trial that was terminated early.

MK-677 is not currently in the FDA pipeline. It is not a compound with a projected approval timeline. It is a drug with an extensive clinical history, discontinued development, and active gray-market distribution. The clinical findings are real and published; the risks associated with unregulated sourcing add an additional layer of uncertainty that no trial data can resolve.

Is MK-677 a Peptide?

No. MK-677 is not a peptide, despite being commonly found through peptide-related searches and frequently discussed alongside peptide GH secretagogues such as ipamorelin, hexarelin, and GHRP-2. The confusion is understandable because all of these compounds activate the same receptor. The structural difference is fundamental.

Peptide GH secretagogues are chains of amino acids. Because peptide bonds are cleaved by digestive enzymes, these compounds lose pharmacological activity if taken orally. They require subcutaneous or intravenous administration to reach systemic circulation intact.

MK-677 is a spiropiperidine: a synthetic small molecule built around a non-peptide scaffold. A 1995 paper by Patchett and colleagues in the Proceedings of the National Academy of Sciences describes the design of L-163,191 (MK-0677) as a potent, orally active growth hormone secretagogue, specifically engineered to resist digestive degradation while retaining high-affinity binding at the ghrelin receptor. The compound is orally bioavailable and has an elimination half-life of approximately 24 hours, properties that no peptide-based GH secretagogue possesses.

What MK-677 shares with peptide secretagogues is its pharmacological target: the ghrelin receptor (GHSR-1a). Activating this receptor stimulates the same downstream effect: pulsatile GH release from the pituitary and subsequent IGF-1 production from the liver. The route and the molecule are different; the signal and the outcome are similar. That functional equivalence explains why MK-677 consistently appears in the same conversations as ipamorelin and CJC-1295, even though it belongs to a chemically distinct class and is correctly categorized as a small-molecule medication rather than a peptide.

How MK-677 Works in the Body

Ghrelin receptor agonism and pulsatile GH release

The ghrelin receptor (GHS-R1a) is expressed primarily in the pituitary gland and hypothalamus. When ghrelin, the endogenous ligand, binds this receptor, it stimulates the release of growth hormone-releasing hormone (GHRH) from the hypothalamus and directly potentiates GH secretion from pituitary somatotrophs. MK-677 binds the same receptor with high affinity and produces the same upstream signal. A foundational 1996 randomized controlled trial by Chapman and colleagues, published in the Journal of Clinical Endocrinology and Metabolism, demonstrated that daily oral MK-677 at 25 mg in healthy elderly subjects (ages 64 to 81; N = 32) increased mean 24-hour GH concentrations by 97% and raised IGF-1 levels into the normal young-adult range within two to four weeks. Critically, the compound enhanced pulsatile GH secretion without changing pulse frequency, meaning it amplifies the physiological pattern of GH release rather than producing a sustained supraphysiological surge.

Oral bioavailability and half-life advantage

The pharmacokinetic profile of MK-677 is its most clinically relevant distinguishing feature relative to peptide GH secretagogues. Its non-peptide structure confers oral bioavailability and an elimination half-life of approximately 24 hours, enabling once-daily dosing. A 7-day RCT in healthy young men by Copinschi and colleagues, published in the Journal of Clinical Endocrinology and Metabolism in 1996, confirmed sustained 24-hour GH secretion and IGF-1 elevation on daily oral dosing, with no change in mean cortisol levels or urinary free cortisol. This is an important safety parameter, as some GH secretagogues produce meaningful adrenocortical activation. At therapeutic doses across multiple trials, cortisol and prolactin effects were minimal.

Downstream IGF-1 elevation

The primary pharmacodynamic outcome of GHSR-1a agonism is hepatic IGF-1 production. GH released from the pituitary travels to the liver, where it stimulates IGF-1 synthesis. IGF-1 mediates most of GH's anabolic and metabolic effects: protein synthesis, muscle maintenance, bone turnover, and adipose tissue metabolism. Across Merck's clinical program, MK-677 consistently and reliably raised serum IGF-1, including in GH-deficient adults, obese males, elderly hip fracture patients, and hemodialysis patients. A 1997 study by Chapman and colleagues published in the Journal of Clinical Endocrinology and Metabolism confirmed that oral MK-677 stimulated the GH/IGF-1 axis in nine severely GH-deficient adults, with IGF-1 increasing 52% at 10 mg and 79% at 50 mg after oral administration. Codner and colleagues, in a 2001 randomized controlled trial published in Clinical Pharmacology and Therapeutics, extended this line of work into 18 prepubertal children with GH deficiency (15 male, 3 female; mean age 10.6 years) dosed orally at 0.2 mg/kg for 7 days or 0.8 mg/kg for 7–8 days; at the 0.8 mg/kg dose, median peak GH rose by 3.8 μg/L (p = 0.001), IGF-1 increased by a median 12 μg/L (p = 0.01), and IGFBP-3 rose by 0.4 μg/L (p = 0.01), though individual responses varied substantially and the small cohort and short duration limit inference about long-term growth outcomes. Campbell and colleagues, publishing in Nephrology Dialysis Transplantation in 2018, conducted a 3-month crossover study in 26 enrolled hemodialysis patients (22 completers) in which oral MK-0677 produced a 1.76-fold geometric-mean increase in IGF-1 (95% CI 1.48–2.10; p < 0.001) and a 65% greater IGF-1 rise versus placebo (95% CI 33–104%; p < 0.001) with no serious attributable adverse events — a niche data point establishing that the ghrelin-receptor pathway remains engageable in end-stage renal disease, though the small completer cohort and short duration preclude inference about functional or mortality outcomes. The compound's ability to raise IGF-1 is not disputed. Whether that reliably translates to meaningful clinical outcomes is a different question, and Merck's trial program answered it in ways that halted development.

Effects on sleep architecture

A notable secondary pharmacodynamic observation from Merck's early trials was an effect on sleep quality. A 1997 polysomnography RCT by Copinschi and colleagues, published in Neuroendocrinology, randomized healthy young and older adults to 7-day MK-677 or placebo and found an approximately 50% increase in stage IV slow-wave sleep in younger subjects and approximately 50% increases in REM sleep duration in older subjects, with decreased abnormal sleep episodes in both groups. GH secretion is physiologically coupled to slow-wave sleep, and GH secretagogues appear to reinforce this coupling. The clinical significance of improved sleep architecture metrics in otherwise healthy research volunteers has not been established in longer trials.

What Merck's Clinical Program Found

Body composition in obese males (1998)

An 8-week double-blind RCT by Svensson and colleagues, published in the Journal of Clinical Endocrinology and Metabolism in 1998, randomized 24 obese males to MK-677 25 mg or placebo. MK-677 increased fat-free mass, increased basal metabolic rate transiently at week 2 (but not week 8), and raised IGF-1. The glucose signal appeared in this study: while fasting glucose and insulin were unchanged, an oral glucose tolerance test showed impaired glucose homeostasis at weeks 2 and 8. This was the first controlled human trial to document the body-composition and metabolic-perturbation tradeoff that would persist across Merck's program.

Bone turnover (1998 to 1999)

MK-677 consistently increased markers of both bone formation (osteocalcin, bone-specific alkaline phosphatase) and bone resorption (N-telopeptide) in controlled trials. An 8-week RCT in 24 obese young males by Svensson and colleagues, published in the Journal of Bone and Mineral Research in 1998, found formation markers rising 23 to 28% and resorption markers rising 23 to 46%. A follow-up 9-week study by Murphy and the MK-677 Study Group, published in the Journal of Bone and Mineral Research in 1999, extended these findings to healthy and functionally impaired elderly adults. The coupled turnover pattern suggested that elevated IGF-1 was activating bone remodeling, not selectively building bone mass.

Bone mineral density in postmenopausal women: negative result

Whether increased bone turnover translated to increased bone density was tested directly. A 12-month RCT by Murphy and colleagues, published in the Journal of Clinical Endocrinology and Metabolism in 2001, randomized postmenopausal osteoporotic women to MK-677 alone, alendronate alone, MK-677 plus alendronate, or placebo. MK-677 alone did not significantly increase bone mineral density at any measured site versus placebo. Adding MK-677 to alendronate produced no additional benefit over alendronate alone, except for a modest femoral neck advantage (4.2% vs. 2.5%, p < 0.05). The negative result corrected a common inference: restoring IGF-1 to young-adult levels does not automatically produce meaningful bone accrual. It accelerates remodeling, but remodeling and net accumulation are not the same process.

Hip fracture trials: biomarker improvement without functional benefit

The most clinically ambitious use case in Merck's program was functional recovery from hip fracture in elderly patients. Two trials addressed this directly. A 2004 multicenter RCT by Bach and colleagues, published in the Journal of the American Geriatrics Society, enrolled 161 ambulatory adults aged 65 and older who had recently sustained hip fractures across 13 sites in a six-month double-blind, placebo-controlled trial. MK-677 raised serum IGF-1 by 84% compared with 17% on placebo, but although MK-677 patients showed numerically greater improvement on three of four lower-extremity functional performance measures, none reached statistical significance versus placebo. A subsequent Phase IIb multicenter RCT by Adunsky and colleagues, published in Archives of Gerontology and Geriatrics in 2011, randomized 123 elderly hip fracture patients to MK-677 or placebo. The primary functional recovery endpoint was not met, and the trial was terminated early due to a safety signal of congestive heart failure in the treatment arm. IGF-1 restoration in elderly patients recovering from hip fracture did not produce the functional gains the hypothesis predicted.

The pivotal 2-year aging trial

The most comprehensive clinical assessment of MK-677 in healthy older adults was a 2-year double-blind randomized modified-crossover trial by Nass and colleagues, published in the Annals of Internal Medicine in 2008. The trial enrolled 65 healthy adults aged 60 to 81 (23 men, 25 women on hormone replacement therapy, 17 women off HRT) and randomized them to oral MK-677 25 mg daily or placebo. On the efficacy side: MK-677 restored GH and IGF-1 to young-adult levels and increased fat-free mass by 1.1 kg (versus a decrease of 0.5 kg with placebo; p < 0.001). Appetite increased, as expected from ghrelin receptor agonism. On the safety side: fasting blood glucose increased by an average of 0.3 mmol/L (5 mg/dL) and insulin sensitivity decreased. The most frequently reported side effects were appetite increase, transient mild lower-extremity edema, and muscle pain. The key finding for development decisions was that increased fat-free mass did not result in changes in strength or function, confirming the pattern seen in the hip fracture trials. IGF-1 elevation could shift body composition measurements without producing the clinical outcomes the body-composition hypothesis predicted.

The Alzheimer's disease trial: negative result in cognition

Given the hypothesis that IGF-1 signaling plays a role in neurotrophic support and amyloid-beta clearance, Merck also ran a large Alzheimer's trial. A 12-month double-blind multicenter RCT by Sevigny and colleagues, published in Neurology in 2008, randomized 563 patients with mild-to-moderate Alzheimer's disease to MK-677 or placebo. MK-677 raised IGF-1 by 60.1% at 6 weeks and 72.9% at 12 months, confirming pharmacological target engagement. There were no significant differences between groups on any clinical endpoint: the CIBIC-plus, ADAS-Cog, ADCS-ADL, and CDR-sob scores were statistically indistinguishable at all timepoints. The finding established that sustained IGF-1 elevation, despite robust target engagement, did not slow Alzheimer's disease progression. Preclinical data in mouse models of Alzheimer's pathology had suggested a different outcome; a 2018 study by Jeong and colleagues, published in the International Journal of Molecular Sciences, reported that MK-0677 alleviated amyloid-beta pathology in the 5XFAD transgenic mouse model, but this preclinical signal did not translate to clinical benefit in the Sevigny trial — a further illustration that rodent amyloid findings routinely fail to reproduce in human Alzheimer's trials.

MK-677 Compared to Peptide GH Secretagogues and Other GH-Axis Compounds

MK-677 activates the same receptor as peptide GH secretagogues (ipamorelin, GHRP-2, GHRP-6, hexarelin), but through a non-peptide scaffold. The most meaningful clinical distinctions involve route of administration, half-life, and regulatory status. No head-to-head trials have compared MK-677 to any peptide GH secretagogue. Cross-compound comparisons are unreliable due to differences in study design, patient populations, doses, and endpoints. Interpret the following as mechanistic context, not efficacy ranking.

Compared to ipamorelin and other peptide GH secretagogues

Peptide secretagogues such as ipamorelin require subcutaneous injection and have short half-lives (typically 2 to 4 hours), requiring multiple daily administrations to maintain sustained IGF-1 elevation. MK-677's oral bioavailability and 24-hour half-life eliminate these administration burdens. The selectivity profiles differ: ipamorelin produces minimal cortisol and prolactin stimulation, a property shared by MK-677 at therapeutic doses. The regulatory contexts are entirely different. As of April 2026, ipamorelin is classified as an FDA Category 2 bulk drug substance (restricted from compounding pending review), while MK-677 has no compounding pathway at all. MK-677 has never received FDA authorization for human use and has no approved drug substance status.

Compared to sermorelin and tesamorelin (GHRH analogs)

Sermorelin and tesamorelin act upstream: they are synthetic GHRH analogs that stimulate GH release by activating the GHRH receptor on pituitary somatotrophs, rather than the ghrelin receptor. Tesamorelin (brand name Egrifta) is FDA-approved for HIV-associated lipodystrophy, making it the only compound in the GH-axis secretagogue category with an approved indication. Sermorelin was previously approved and is currently available as a Category 1 compounded prescription. MK-677 operates through a distinct mechanism (ghrelin receptor vs. GHRH receptor) and has no approved indication or legal pathway for human use.

Compared to exogenous HGH

Recombinant human growth hormone (rhGH) delivers exogenous GH directly via injection and suppresses endogenous GH pulsatility. MK-677 preserves the physiological pulsatile pattern by stimulating the hypothalamic-pituitary axis rather than bypassing it. In Chapman and colleagues' 1996 trial, MK-677 raised IGF-1 to young-adult levels in healthy elderly subjects, achieving a pharmacodynamic outcome comparable to low-dose rhGH replacement without parenteral administration. Whether preservation of pulsatility produces meaningfully different clinical outcomes relative to continuous exogenous GH has not been established in comparative trials. This comparison is for scientific context only; exogenous HGH is an FDA-approved prescription product (approved for specific indications in adults and children) and is a fundamentally different compound with a different regulatory status and evidence base.

Side Effects and Safety Signals

The adverse event profile for MK-677 is derived from Merck's clinical trial program, which studied mostly healthy elderly adults and clinical populations. Effects observed in gray-market users combining MK-677 with unapproved compounds (SARMs, for example) cannot be attributed to MK-677 alone.

Common (reported in clinical studies):

• Increased appetite: Expected consequence of ghrelin receptor agonism. Ghrelin is the endogenous appetite-stimulating hormone; its receptor agonist predictably increases food intake.
• Transient lower-extremity edema: Reported in multiple trials; typically mild and reversible.
• Muscle pain (myalgia): Reported across multiple trials; typically mild.
• Elevated fasting glucose: A consistent finding across multiple Merck trials: the 1998 Svensson obese-male study found impaired glucose tolerance on testing; the 2008 Nass two-year trial documented a 0.3 mmol/L rise in fasting glucose; and the 1997 Chapman study in GH-deficient adults noted increases in fasting and postprandial insulin and glucose. IGF-1 promotes insulin resistance independent of GH, and ghrelin receptor activation itself affects insulin secretion and sensitivity.
• Elevated HbA1c: Consistent with the fasting glucose signal across trials of sufficient duration to capture glycemic trajectory.

Less common but reported or noted:

• Congestive heart failure signal: The Phase IIb hip fracture trial by Adunsky and colleagues, published in Archives of Gerontology and Geriatrics in 2011, enrolled 123 elderly hip fracture patients (62 MK-0677, 61 placebo, 25 mg/day) and was terminated early after 4 of 62 patients in the MK-0677 arm (6.5%) developed congestive heart failure versus 1 of 61 (1.7%) on placebo; the authors concluded the drug had an unfavorable safety profile in this population. No CHF imbalance was reported in the Nass and colleagues 2008 two-year trial in healthier community-dwelling older adults, which suggests the CHF signal is most relevant to frail elderly patients with acute illness rather than to the broader older-adult population. The mechanism is not fully characterized.
• Insulin resistance: Reduced insulin sensitivity was documented in the Nass 2008 trial and in the Svensson 1998 glucose tolerance test data. The ghrelin receptor has direct effects on pancreatic beta-cell function and insulin secretion, complicating the metabolic picture beyond secondary IGF-1 effects alone.
• Cortisol: In 1996, Copinschi and colleagues found no change in 24-hour mean cortisol levels at therapeutic doses, with only a minor timing shift in the nocturnal nadir. This distinguishes MK-677 from some other secretagogues with meaningful adrenocortical activation.
• Prolactin: In 1996, Chapman and colleagues documented modest increases of approximately 23% at 25 mg; these remained within the normal range.

A 2018 review by Sigalos and Pastuszak, published in Sexual Medicine Reviews, summarized the GH secretagogue safety profile as generally well tolerated in trials, with the primary ongoing concern centered on glucose metabolism effects and the unresolved question of long-term cancer risk. Given that IGF-1 signaling promotes cell proliferation, long-term IGF-1 elevation warrants surveillance for cancer incidence that Merck's discontinued program never completed.

Who Should Not Use MK-677

Because MK-677 is not FDA-approved and is not prescribed by licensed providers, no formal contraindication list derived from an approved prescribing information document exists. Based on the compound's pharmacology and the adverse events documented in clinical trials, the following groups face elevated risk.

• People with diabetes, prediabetes, or insulin resistance: MK-677 consistently elevates fasting glucose and impairs glucose tolerance across trial populations. Worsening glycemic control is a documented pharmacological consequence, not a theoretical risk.
• People with cardiac history or risk factors, particularly elderly individuals: The CHF signal documented in the 2011 Adunsky trial and observed in the 2008 Nass full publication is most relevant to older adults and those with pre-existing cardiovascular risk. The mechanism is not resolved.
• People with active or suspected malignancy: Sustained IGF-1 elevation promotes cell proliferation. IGF-1 is a growth factor with well-established roles in tumor biology. Long-term safety data sufficient to evaluate cancer incidence in MK-677-treated populations does not exist. This is an unresolved mechanistic risk.
• Pregnant and breastfeeding individuals: No safety data exist in pregnancy or lactation. MK-677 should not be used in these populations.
• People purchasing from unregulated gray-market sources: A 2025 retrospective and prospective analysis by Barrios and colleagues, published in Drug Testing and Analysis, examined 324 products from the GEON network of illegal sports-performance products and found ibutamoren as one of the five most frequently detected compounds. Approximately 65% of products were misrepresented as medicines, 24% were labeled as dietary supplements, and many were misdosed, with some delivering overdoses. There is no quality assurance for gray-market MK-677. Contamination, incorrect dosing, and misidentified compounds are documented risks.

This list reflects the compound's known pharmacology and published trial data. Because no licensed provider evaluates eligibility before use in a gray-market context, these risks are borne entirely by the individual without clinical oversight.

Regulatory Status and Legal Context

As of April 2026, MK-677 (ibutamoren mesylate) is not FDA-approved for any indication. No New Drug Application was submitted. Merck investigated MK-677 as an investigational new drug (IND) for multiple indications including age-related muscle loss, hip fracture recovery, growth hormone deficiency, and Alzheimer's disease. The pivotal aging trial published by Nass and colleagues in 2008, the Alzheimer's trial by Sevigny and colleagues in 2008, and the hip fracture programs by Bach and colleagues in 2004 and Adunsky and colleagues in 2011 collectively produced results that led Merck to discontinue development. No sponsor has subsequently advanced MK-677 through the FDA approval pathway.

MK-677 is not a bulk drug substance listed by the FDA as eligible for compounding under Section 503A or Section 503B. It has no category designation within the FDA's bulk compounding framework because it was never approved as a drug substance for human use. Compounding facilities cannot legally compound MK-677 for human administration under current FDA regulations.

Products labeled as "MK-677" or "ibutamoren" sold online are marketed under "research chemical" or "not for human use" designations. This framing does not change the legal reality: the FDA has not authorized these products for human consumption. A 2025 analysis within the GEON network documented that MK-677 is one of the most frequently seized compounds in suspected illegal sports-performance product investigations across multiple jurisdictions. Cardaci and colleagues, in a 2022 case report published in Experimental Physiology, characterized the real-world pattern in which MK-677 is used outside of supervised clinical research: a recreational user stacking LGD-4033 (a SARM) with MK-677, with body-composition changes, androgen-receptor content, and circulating biomarkers tracked across the cycle. The report does not validate any safety or efficacy claim; it illustrates how gray-market combinations operate in practice, without medical oversight or quality assurance on the compounds involved.

As of the 2026 WADA Prohibited List, growth hormone secretagogues (including ghrelin mimetics) are prohibited in-competition and out-of-competition under Section S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics). Athletes subject to anti-doping testing should consult their governing body before exposure to any substance in this class, including through contaminated supplements.

Understanding the Biomarkers MK-677 Targets

Whether or not MK-677 is part of anyone's clinical picture, the biomarkers it activates and perturbs are measurable and meaningful independent of any specific compound. Understanding these values provides an objective baseline relevant for anyone exploring GH-axis physiology, evaluating secretagogue science, or assessing their own metabolic risk profile before pursuing any intervention in this class.

• IGF-1 (Insulin-Like Growth Factor 1): The primary downstream marker of GH axis activity and the compound's intended therapeutic target. IGF-1 declines with age; MK-677's entire rationale is built on restoring it. Baseline IGF-1 establishes where you are on the age-related decline curve and whether GH axis activity is a relevant variable for your current physiology.
• HbA1c (Hemoglobin A1c): The 3-month average of blood glucose, and the marker most sensitive to the glycemic perturbation documented consistently in MK-677 trials. Anyone evaluating secretagogue science should know their baseline HbA1c. Elevated HbA1c at baseline increases the clinical significance of any further glucose perturbation.
• Fasting glucose: Elevated fasting glucose was documented in the Nass 2008 trial and in the Svensson 1998 glucose tolerance test. Fasting glucose provides a point-in-time metabolic picture that complements HbA1c's longitudinal view.
• Fasting insulin: Reduced insulin sensitivity is a documented consequence of MK-677 use. Baseline fasting insulin, interpreted alongside glucose, provides an estimate of insulin resistance independent of HbA1c. Elevated fasting insulin at baseline signals pre-existing insulin resistance that compounds which impair sensitivity further would be expected to worsen.
• Growth hormone (GH): Direct measurement of basal GH or stimulated GH (via provocative testing) is used clinically to assess GH axis function. Serum GH alone is limited by its pulsatile nature; IGF-1 is the more interpretable marker for baseline status.
• Cortisol: Minimal cortisol effect was observed with MK-677 at therapeutic doses across multiple trials. Nonetheless, cortisol is a relevant baseline marker for anyone exploring GH secretagogue science, as adrenocortical activation varies across secretagogue classes.

That principle, measuring first and then evaluating, is central to Superpower's approach to preventive health. The compounds in this space continue to evolve. The value of knowing your baseline does not.

IMPORTANT SAFETY INFORMATION

MK-677 (ibutamoren mesylate) is NOT FDA-approved for any indication. Merck's investigational new drug program was discontinued; no New Drug Application was submitted. MK-677 is not available by prescription from any licensed provider. It is not eligible for compounding under FDA Section 503A or Section 503B regulations. Superpower is a technology platform; Superpower does not prescribe, sell, compound, or facilitate access to MK-677 or any product containing ibutamoren.

MK-677 is currently distributed as a "research chemical" through unregulated gray-market channels. Products purchased through these channels have not been evaluated by the FDA for safety, efficacy, identity, strength, quality, or purity. Independent analyses have found mislabeled, misdosed, and contaminated products in gray-market GH secretagogue supply chains.

Warnings: Elevated fasting glucose and impaired glucose tolerance (documented across multiple clinical trials; individuals with diabetes, prediabetes, or insulin resistance face elevated risk); reduced insulin sensitivity; congestive heart failure signal in elderly trial populations (the 2011 Adunsky hip fracture trial was terminated early due to a CHF safety signal); transient lower-extremity edema; increased appetite (expected consequence of ghrelin receptor agonism); muscle pain; modest prolactin elevation within normal range at therapeutic doses.

Unresolved long-term safety concerns: Sustained IGF-1 elevation promotes cell proliferation. Long-term cancer incidence data from adequately powered human trials does not exist for MK-677 because the clinical program was discontinued before follow-up duration was sufficient to characterize oncological risk.

As of the 2026 WADA Prohibited List, growth hormone secretagogues, including ghrelin mimetics such as MK-677, are prohibited in-competition and out-of-competition under Section S2. Athletes subject to anti-doping testing should consult their governing body.

Not a complete list of risks. Because MK-677 has no FDA-approved prescribing information, no comprehensive safety profile derived from post-market surveillance exists. The adverse events described above are derived from Merck's clinical trial publications only and may not reflect outcomes in gray-market users combining MK-677 with other unapproved compounds.

Additional Questions

What are the safety concerns with MK-677?

The primary documented safety concerns from clinical trials are glucose perturbation (elevated fasting glucose, elevated HbA1c, reduced insulin sensitivity) and cardiovascular signals in elderly populations (a congestive heart failure imbalance in the Adunsky 2011 hip fracture trial). Additional gray-market risks include product quality: a 2025 analysis of seized gray-market products found MK-677 in mislabeled formulations, often combined with other unapproved compounds, with many products overdosed relative to labeled concentrations. Long-term cancer risk from sustained IGF-1 elevation has not been characterized because Merck's program ended before sufficient long-term follow-up was completed.

Can I get MK-677 through a compounding pharmacy?

No. MK-677 is not eligible for compounding under FDA regulations. It is not an FDA-approved drug substance and has no bulk drug substance designation under Section 503A or 503B. Licensed compounding pharmacies cannot legally compound MK-677 for human use. Products marketed as compounded or pharmaceutical-grade MK-677 do not have legal authorization, regardless of how they are labeled.

What is the relationship between MK-677 and growth hormone deficiency?

MK-677 stimulates the GH/IGF-1 axis and was studied in adults with GH deficiency; a 1997 trial by Chapman and colleagues confirmed dose-dependent IGF-1 elevation in nine severely GH-deficient adults. However, MK-677 is not FDA-approved for growth hormone deficiency, and the compound never completed the regulatory pathway required to establish it as a treatment for any condition. Approved options for GH deficiency include recombinant human growth hormone (rhGH) products with established regulatory status and prescribing information.