Ibutamoren
MK-677
Growth Hormone
CAS
159752-10-0
Molecular Weight
529
Da
Observational
An orally active non-peptide compound that mimics ghrelin to stimulate sustained growth hormone and IGF-1 release. The only compound in this catalog that achieves growth hormone secretagogue effects without injection — a significant practical advantage. Has reached Phase II human clinical trials for muscle wasting and hip fracture recovery. Widely used in fitness and longevity communities. Sold as a research compound, not FDA approved.
Oral · Liquid
Intranasal Suitable
No
Research Compound
Community Signal
Community signal is high-volume and more mixed than any Growth Hormone compound. Ibutamoren's oral bioavailability and low cost make it widely used, producing a large and diverse anecdotal pool. Sleep quality improvements are the most consistently reported benefit, often described as dramatic within days of starting. Hunger increase is almost universally reported and is the most common reason for discontinuation. Water retention and mild edema are frequent early side effects. Long-term use reports raise questions about insulin sensitivity and blood glucose, a concern the more sophisticated community segments take seriously. r/PEDs and r/Peptides both have extensive Ibutamoren threads. The community debate about whether it causes lasting GH axis suppression is unresolved.
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What It Is
MK-677, also known as Ibutamoren, is a non-peptide small molecule growth hormone secretagogue developed originally by Reverse Pharmacology and later acquired by Merck. Despite not being a peptide itself it is consistently grouped with peptides in the performance and longevity community because it operates through the same ghrelin receptor pathway as Ipamorelin and Sermorelin. Unlike injectable growth hormone secretagogue peptides, MK-677 is orally active, a significant practical advantage that has contributed to its widespread use. It reached Phase II clinical trials for muscle wasting, growth hormone deficiency, and hip fracture recovery before development was discontinued for commercial reasons.
Mechanism of Action
MK-677 is a potent, long-acting ghrelin mimetic, it binds to and activates the ghrelin receptor (GHS-R1a) in the pituitary gland, stimulating sustained growth hormone release and subsequently elevating IGF-1 levels. Unlike peptide secretagogues that produce short GH pulses, MK-677's oral bioavailability and 24-hour half-life produce a more sustained elevation of GH and IGF-1. It does not suppress the body's natural GH axis in the way exogenous HGH does, making it theoretically safer for long-term use, though long-term human data remains limited.
Use Cases
MK-677 is used in the performance and longevity community for lean muscle mass development, fat loss, improved sleep quality (GH is predominantly released during deep sleep), increased bone mineral density, and anti-aging protocols. Human clinical trial data exists for muscle wasting in elderly populations and hip fracture recovery, giving it a stronger evidence base than most research compounds in this space. It is one of the most popular compounds in the fitness biohacker community due to its oral convenience relative to injectable alternatives.
Known Risks
MK-677 has a more established human safety profile than most compounds in this catalog given its clinical trial history. Known side effects include increased appetite (it mimics ghrelin which stimulates hunger), water retention, elevated fasting blood glucose, lethargy, and tingling or numbness in extremities. The sustained IGF-1 elevation raises theoretical long-term cancer concerns consistent with other GH-stimulating compounds, individuals with active malignancies or strong family history should avoid. Not recommended during pregnancy. May worsen insulin resistance with prolonged use, monitoring blood glucose is advisable.
Available Forms
Oral capsules and liquid solution, the primary advantage of MK-677 over injectable secretagogues. Sold as a research compound through research chemical vendors. No prescription pathway currently exists. Widely available online though quality varies significantly between suppliers, third party COA verification strongly recommended.
Regulatory Status
Not FDA approved for human use. Sold as a research compound labeled "not for human consumption." Not a controlled substance. Exists in the same legal gray zone as BPC-157 and TB-500. Was listed by WADA (World Anti-Doping Agency) as a prohibited substance in competitive sports, athletes subject to drug testing should be aware.
Sources
https://pubmed.ncbi.nlm.nih.gov/8954023/
https://pubmed.ncbi.nlm.nih.gov/18981485/
https://pubmed.ncbi.nlm.nih.gov/9467534/
Similar Compounds
Ipamorelin, Sermorelin, CJC-1295, Turkesterone
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