MK-677 has been evaluated in controlled human studies lasting up to 2 years. The most consistent safety concerns are increased fasting glucose and insulin resistance, which may be problematic in metabolically at-risk populations. Appetite stimulation and mild edema are common. Long-term effects of sustained IGF-1 elevation are unknown. Always discuss with a physician.

Does MK-677 build muscle?

Some studies show modest increases in lean body mass (~1-2 kg) in elderly and GH-deficient populations. However, the largest muscle-wasting trial failed its primary endpoint despite robust GH/IGF-1 elevation. MK-677 is not a reliable muscle-building compound based on available evidence.

No. MK-677 is not a steroid. It is a non-peptide ghrelin receptor agonist that stimulates your body's own growth hormone production. It does not directly introduce exogenous hormones.

Is MK-677 FDA-approved?

No. MK-677 is not FDA-approved for any indication. Clinical development was discontinued after the hip fracture trial did not meet its primary endpoint. It is classified as an investigational compound and is prohibited by WADA.

What about insulin resistance?

Increased fasting glucose and insulin resistance are the most clinically significant safety concerns with MK-677, particularly with prolonged use. This is dose-dependent and makes the compound potentially problematic for elderly or metabolically at-risk populations. Blood glucose monitoring is recommended.

Have any randomized controlled human trials been completed?

Oral GH secretagogue. One of the few compounds that reliably elevates GH and IGF-1 via an oral route in controlled human studies. This oral bioavailability distinguishes MK-677 from injectable GH secretagogues like CJC-1295 and ipamorelin, though the clinical implications of sustained oral GH elevation remain debated

What does the research show about: IGF-1 levels elevated to young-adult range in elderly subjects across multiple s?

IGF-1 levels elevated to young-adult range in elderly subjects across multiple studies lasting 2-12 months. Consistent IGF-1 elevation is the most reliably demonstrated effect, but whether normalizing IGF-1 in elderly populations produces meaningful clinical outcomes has not been confirmed

What does the research show about: Failed to meet primary endpoints in the largest muscle-wasting trial (hip fractu?

Failed to meet primary endpoints in the largest muscle-wasting trial (hip fracture recovery), despite consistent GH/IGF-1 elevation. This disconnect between biomarker improvement and functional outcomes is the central limitation of the MK-677 evidence base

What does the research show about: No FDA approval pursued despite multiple completed clinical trials. Development ?

No FDA approval pursued despite multiple completed clinical trials. Development was discontinued. The decision not to advance MK-677 through regulatory approval, despite available human data, suggests the risk-benefit profile was not considered favorable by the sponsor

reviewed april 2026|next review october 2026|88 physicians psi has verified|134 published studies

MK-677 (Ibutamoren)

MK-677 (ibutamoren) is a non-peptide, orally bioavailable ghrelin mimetic that reliably elevates GH and IGF-1 levels in human clinical trials lasting up to 2 years. It is the only oral growth hormone secretagogue to reach multi-year human trials. Clinical development was discontinued.

Evidence landscape: 134 published studies

134 published items. 24 human studies and 82 animal studies. The most extensive human dataset of any GH secretagogue.

24 Human
82 Animal
28 Reviews

Not FDA-approved. Clinical development was discontinued. Placed on the FDA's Category 2 list (a designation that temporarily prevented licensed pharmacies from preparing this compound), meaning licensed pharmacies could not prepare it. It is expected to return to Category 1 (legal for pharmacy preparation) following the February 2026 HHS announcement.

Multiple human trials up to 2 years confirm GH and IGF-1 elevation. The largest trial designed to test clinical benefit (hip fracture recovery) failed its primary endpoint despite sustained biomarker improvement.

The only oral GH secretagogue with multi-year human data. Less selective than ipamorelin (raises cortisol and appetite) but does not require injection.

PSI Assessment

The only orally bioavailable growth hormone secretagogue ever to reach multi-year human clinical trials is not a peptide at all. MK-677 (ibutamoren) is a non-peptide ghrelin mimetic that reliably elevates GH and IGF-1 through an oral dose, confirmed across studies lasting up to 2 years. The biomarker data is consistent and robust. The gap is between biomarker elevation and functional outcomes: the largest trial, designed to test whether GH elevation improves hip fracture recovery, failed its primary endpoint despite sustained IGF-1 increases. Clinical development was discontinued.

The only oral GH secretagogue with multi-year human data. Biomarker elevation is robust. The hip fracture trial designed to prove clinical benefit failed.

The mechanism is ghrelin receptor (GHS-R1a) agonism. MK-677 mimics the hunger hormone ghrelin, triggering pulsatile GH release from the pituitary. This is also why increased appetite is the most consistent side effect. Unlike exogenous GH injection, it preserves the natural pulsatile secretion pattern. The insulin resistance signal is the primary safety concern.

What the evidence supports

MK-677 reliably increases GH and IGF-1 levels in humans across multiple clinical trials lasting up to 2 years. Oral bioavailability is confirmed and distinguishes it from injectable alternatives. Sleep architecture improvements (REM duration) are documented. The ghrelin receptor mechanism is well-characterized.

What is not yet established

Whether MK-677's hormonal increases translate to meaningful improvements in functional outcomes like strength, fracture prevention, or quality of life. The largest trial designed to test clinical benefit (hip fracture recovery) failed its primary endpoint. Long-term safety beyond 2 years. Whether insulin resistance and appetite stimulation limit usefulness in non-cachectic populations.

Research Evidence

The findings below cover the confirmed biomarker data, the failed functional outcomes trial, and the safety signals.

Evidence by condition

Evidence dimensions across MK-677 indications. Biomarker elevation has strong multi-trial confirmation. Functional outcome data is limited and the largest trial failed.

Condition	Mechanism	Animal evidence	Human evidence	Replication
GH Deficiency
Muscle Wasting
Bone Density
Sleep Quality
Appetite Stimulation

MK-677 reliably elevates GH and IGF-1 levels to youthful ranges in elderly adults across multiple clinical trials lasting up to 2 years. The biomarker effect is dose-dependent, sustained, and replicated independently.

Biomarker elevation is the most robustly documented effect. Whether normalizing IGF-1 in elderly populations produces meaningful clinical outcomes has not been confirmed.

The largest trial designed to test clinical benefit - hip fracture recovery in elderly patients - failed its primary endpoint despite sustained IGF-1 increases. Patients receiving MK-677 did not recover faster than placebo.

This trial is the critical data point. It demonstrates that reliable hormone elevation does not guarantee functional improvement. The disconnect between biomarkers and outcomes is MK-677's defining limitation.

Fasting glucose increases and insulin resistance are observed in most human trials. Appetite stimulation is consistent and dose-dependent. These are direct pharmacological consequences of ghrelin receptor activation.

The metabolic side effects are not idiosyncratic - they are mechanistically inherent. This limits the compound's applicability in populations not already experiencing muscle wasting or cachexia.

24 Human|82 Animal|28 Reviews

View all 134 indexed studies

How MK-677 (Ibutamoren) Works

MK-677 is a non-peptide spiropiperidine compound that acts as a functional agonist at the GHS-R1a receptor with high oral bioavailability. It increases GH secretion by amplifying the body's own GHRH signaling and suppressing somatostatin tone, resulting in elevated peak GH pulses without disrupting circadian GH rhythm.

MK-677 is the only GH-boosting compound you can take by mouth instead of injecting. It works by mimicking ghrelin, the hunger hormone, which tells your pituitary gland to release more growth hormone. This is also why increased appetite is one of its most commonly reported effects.

For a more detailed view of the biology, here is what researchers have observed at the molecular level.

MK-677 mimics ghrelin by binding to the growth hormone secretagogue receptor (GHS-R1a) in the hypothalamus and pituitary gland. This triggers pulsatile growth hormone release, which in turn stimulates the liver to produce IGF-1. Unlike exogenous GH injection, MK-677 preserves the body's natural GH pulsatility pattern. It also increases appetite, a direct consequence of ghrelin receptor activation, which is both a therapeutic effect (in wasting conditions) and a side effect (in other contexts).

What is MK-677 (Ibutamoren) being studied for?

Researchers are studying MK-677 (Ibutamoren) across several health conditions. Each condition below is labeled with the strength of evidence that exists for that specific use, not for MK-677 (Ibutamoren) overall. This means a compound can have human studies for one condition but only animal data for another.

GH Deficiency

·Human Trials

Clinical trials show MK-677 increases GH and IGF-1 levels to youthful ranges in elderly adults. A 2-year study in healthy older adults demonstrated sustained IGF-1 elevation.

Limitations: Biomarker elevation does not equal clinical benefit. The largest functional trial (hip fracture recovery) showed no improvement despite robust IGF-1 increases.

Muscle Wasting

·Human Trials

Studies in hip fracture patients and GH-deficient adults show improvements in lean body mass. Effects are modest compared to exogenous GH.

Limitations: Body composition changes are small and not consistently clinically meaningful. Increased appetite may offset fat-loss potential. No trial has shown MK-677 improves functional strength.

Bone Density

·Animal Studies

Two-year data shows increased bone mineral density at the femoral neck in postmenopausal women, though the clinical significance is debated.

Limitations: No fracture-reduction data exists. Bone density improvements are modest and inconsistently replicated.

Sleep Quality

·Animal Studies

MK-677 increased REM sleep duration and sleep quality in clinical studies. This may be related to GH secretion patterns during sleep.

Limitations: Sleep studies used small sample sizes. Clinical significance of sleep architecture changes versus subjective sleep quality is not established.

Appetite Stimulation

·Human Trials

MK-677 consistently increases appetite via ghrelin receptor activation. This is both a therapeutic application (cachexia) and a side effect (for those seeking body composition improvement).

Limitations: Appetite stimulation cannot be separated from the GH-stimulating mechanism. This limits applicability in populations seeking lean mass gains without increased food intake.

Safety and Regulatory Status

FDA Status: Not FDA-approved. Clinical development was discontinued. Placed on the FDA's Category 2 list (a designation that temporarily prevented licensed pharmacies from preparing this compound), meaning licensed pharmacies could not prepare it. It is expected to return to Category 1 (legal for pharmacy preparation) following the February 2026 HHS announcement.

Availability: Available through specialty pharmacies where a licensed pharmacist prepares a medicine from ingredients for an individual patient, pending reclassification to legal pharmacy preparation status.

Class context: Non-peptide ghrelin mimetic. The only oral GH secretagogue with multi-year human data. Less selective than ipamorelin.

Studied in clinical trials lasting up to 2 years. The most common side effects are increased appetite, mild water retention, and transient muscle pain. The most important safety concern is insulin resistance and elevated fasting glucose, particularly with prolonged use.

Peptide Structure

Technical molecular data for researchers and clinicians.

Questions and Comparisons

Questions the evidence raises for a MK-677 (Ibutamoren) discussion.

Comparison and Related Research

MK-677 is most often compared with injectable GH secretagogues. The comparisons below outline how each differs in route, selectivity, and evidence depth.

Head-to-head comparisons

Full research comparisons covering MK-677 (Ibutamoren) and another peptide side by side.

MK-677 (Ibutamoren) vs Ipamorelin

Three-way comparison of MK-677, ipamorelin, and CJC-1295 for growth hormone research. Mechanisms, evidence levels, oral vs. injectable delivery, and safety profiles analyzed.

View full comparison

MK-677 (Ibutamoren) vs IGF-1 LR3

Research comparison of MK-677 and IGF-1 LR3, an oral GH secretagogue versus a direct IGF-1 receptor analog. Mechanisms, evidence levels, administration contexts, and limitations analyzed.

View full comparison

MK-677 (Ibutamoren) vs CJC-1295

MK-677 is oral with more human data. CJC-1295 is injectable with fewer side effects. Evidence-graded comparison of two GH optimization approaches.

View full comparison

MK-677 (Ibutamoren) vs Sermorelin

MK-677 is oral with more data but metabolic side effects. Sermorelin is injectable with a longer safety record. Evidence-graded GH optimization comparison.

View full comparison

MK-677 (Ibutamoren) vs HGH (Somatropin)

MK-677 stimulates your body to make more GH. HGH is the hormone itself. Evidence-graded comparison of indirect vs direct growth hormone approaches.

View full comparison

MK-677 (Ibutamoren) vs Tesamorelin

Tesamorelin is FDA-approved for lipodystrophy. MK-677 is oral with more general GH data. Evidence-graded comparison.

View full comparison

MK-677 (Ibutamoren) vs CJC-1295 + Ipamorelin

The most popular injectable GH stack vs the oral option. Better side effects vs easier dosing. Evidence-graded comparison.

View full comparison

Related compounds

Ipamorelin CJC-1295 Sermorelin Tesamorelin

Frequently Asked Questions

References

Each citation links to the original study on PubMed, the U.S. National Library of Medicine database.

1.Two-year randomized trial testing MK-677 in healthy older adults. The study found that daily oral dosing increased growth hormone and IGF-1 levels to those of younger adults, with gains in lean body mass but also notable increases in fasting glucose and insulin.Nass R et al., 2008 in Ann Intern Med. View on PubMed
2.Clinical study showing that MK-677 reversed the catabolic effects of caloric restriction in healthy volunteers. Participants maintained nitrogen balance and lean mass during a dietary deficit, suggesting the compound could counteract muscle loss during calorie restriction.Murphy MG et al., 1998 in J Clin Endocrinol Metab. View on PubMed
3.Study examining how MK-677 affected sleep architecture in healthy adults. Treatment increased the duration of REM sleep and stage IV deep sleep, with the sleep improvements persisting over the study period.Copinschi G et al., 1997 in Neuroendocrinology. View on PubMed
4.Randomized trial testing whether MK-677 could improve recovery after hip fracture in elderly patients. While IGF-1 levels increased, the primary endpoint of improved functional recovery was not met - an important negative result for this specific application.Bach MA et al., 2004 in J Am Geriatr Soc. View on PubMed

Medical Disclaimer

This content is for educational and informational purposes only and does not constitute medical advice. The information presented reflects published research as indexed by PSI and should not be used to make treatment decisions. Always consult a qualified healthcare provider before starting, stopping, or modifying any treatment.