{"id":"mk-677","name":"MK-677 (ibutamoren)","aliases":["ibutamoren","ibutamoren mesylate","MK-0677","Nutrobal","L-163,191"],"url":"https://lyoresearch.com/compounds/mk-677","class":{"id":"gh-secretagogues","name":"GH secretagogues (GHRPs)","url":"https://lyoresearch.com/classes/gh-secretagogues"},"summary":"MK-677 is a small molecule, not a peptide, that mimics the hunger hormone ghrelin and raises growth hormone and IGF-1 when taken by mouth. Unusually for a grey-market compound, it has been through proper trials. In 65 healthy older adults over a year it raised fat-free mass by about 1.1 kg against a 0.5 kg loss on placebo, with no change in total or visceral fat. In 563 people with Alzheimer's disease it raised IGF-1 by 73% and did nothing for the disease. It has never been approved anywhere and is prohibited in sport.","overall_grade":"B","overall_grade_meaning":"probable, not settled","human_trials":"2 large RCTs (n=65 over 2 yr; n=563 over 1 yr) + small studies","regulatory_status":"Not approved","molecule":{"formula":"C27H36N4O5S","molecular_weight":"528.7","cas":"159634-47-6","pubchem_cid":178024,"note":null},"pharmacokinetics":{"basis":"human","route":"Oral, once daily in the trials","half_life":"Taken by mouth daily in year-long trials; no primary half-life figure was found in the accessible literature (the '24 hours' repeated online could not be traced to a source)","licensed_regimen":null,"product":null,"source":{"title":"Copinschi G, et al. Effects of a 7-day treatment with a novel, orally active, growth hormone secretagogue, MK-677, in normal young men. J Clin Endocrinol Metab 1996;81:2776","url":"https://pubmed.ncbi.nlm.nih.gov/8768828/"}},"outcomes":[{"outcome":"Growth hormone / IGF-1 elevation","grade":"A","grade_meaning":"established in humans","effect_size":"large","adverse":false,"human_studies":"Multiple RCTs","evidence":"Oral daily dosing reliably restores growth hormone and IGF-1 in older adults to the levels of healthy young adults, and raised IGF-1 by 60–73% in a 563-person trial. This effect is not in dispute.","references":[{"citation":"Nass R, Pezzoli SS, Oliveri MC, et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial.","where":"Ann Intern Med, 2008;149(9):601–611","url":"https://pubmed.ncbi.nlm.nih.gov/18981485/"},{"citation":"Sevigny JJ, Ryan JM, Van Dyck CH, et al. Growth hormone secretagogue MK-677: no clinical effect on AD progression in a randomized trial.","where":"Neurology, 2008","url":"https://pubmed.ncbi.nlm.nih.gov/?term=Sevigny+MK-677+Alzheimer+disease+progression+randomized+2008"}],"verbatim":{"text":"Daily administration of MK-677 significantly increased growth hormone and insulin-like growth factor I levels to those of healthy young adults without serious adverse effects.","citation":"Nass R, Pezzoli SS, Oliveri MC, et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial.","url":"https://pubmed.ncbi.nlm.nih.gov/18981485/"}},{"outcome":"Lean mass (older adults)","grade":"B","grade_meaning":"probable, not settled","effect_size":"small","adverse":false,"human_studies":"1 RCT (n=65, 12 months)","evidence":"Fat-free mass rose by about 1.1 kg over a year against a 0.5 kg loss on placebo — a real difference, in one trial, in people over 60. Whether that becomes strength or function was not shown; the authors themselves called for functional studies.","references":[{"citation":"Nass R, Pezzoli SS, Oliveri MC, et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial.","where":"Ann Intern Med, 2008;149(9):601–611","url":"https://pubmed.ncbi.nlm.nih.gov/18981485/"}],"verbatim":{"text":"Mean fat-free mass decreased in the placebo group but increased in the MK-677 group (change, -0.5 kg [95% CI, -1.1 to 0.2 kg] vs. 1.1 kg [CI, 0.7 to 1.5 kg], respectively; P < 0.001), as did body cell mass, as reflected by intracellular water (change, -1.0 kg [CI, -2.1 to 0.2 kg] vs. 0.8 kg [CI, -0.1 to 1.6 kg], respectively; P = 0.021).","citation":"Nass R, Pezzoli SS, Oliveri MC, et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial.","url":"https://pubmed.ncbi.nlm.nih.gov/18981485/"}},{"outcome":"Fat loss","grade":"B","grade_meaning":"probable, not settled","effect_size":"not measurable","adverse":false,"human_studies":"1 RCT (n=65) — no effect","evidence":"Neither total fat mass nor abdominal visceral fat changed over a year; limb fat actually rose more on MK-677 than on placebo. Sold for fat loss, it did the opposite in the one trial that measured it.","references":[{"citation":"Nass R, Pezzoli SS, Oliveri MC, et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial.","where":"Ann Intern Med, 2008;149(9):601–611","url":"https://pubmed.ncbi.nlm.nih.gov/18981485/"}],"verbatim":{"text":"No significant differences were observed in abdominal visceral fat or total fat mass; however, the average increase in limb fat was greater in the MK-677 group than the placebo group (1.1 kg vs. 0.24 kg; P = 0.001).","citation":"Nass R, Pezzoli SS, Oliveri MC, et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial.","url":"https://pubmed.ncbi.nlm.nih.gov/18981485/"}},{"outcome":"Alzheimer's disease progression","grade":"A","grade_meaning":"established in humans","effect_size":"not measurable","adverse":false,"human_studies":"1 RCT (n=563, 12 months) — negative","evidence":"A year of 25 mg daily in mild-to-moderate Alzheimer's raised IGF-1 substantially and changed none of the four clinical measures. A clean negative: the target was engaged, and it made no difference.","references":[{"citation":"Sevigny JJ, Ryan JM, Van Dyck CH, et al. Growth hormone secretagogue MK-677: no clinical effect on AD progression in a randomized trial.","where":"Neurology, 2008","url":"https://pubmed.ncbi.nlm.nih.gov/?term=Sevigny+MK-677+Alzheimer+disease+progression+randomized+2008"}],"verbatim":{"text":"Despite evidence of target engagement as indicated by an increase in serum insulin-like growth factor-1, the human growth hormone secretagogue MK-677 25 mg was ineffective at slowing the rate of progression of Alzheimer disease.","citation":"Sevigny JJ, Ryan JM, Van Dyck CH, et al. Growth hormone secretagogue MK-677: no clinical effect on AD progression in a randomized trial.","url":"https://pubmed.ncbi.nlm.nih.gov/?term=Sevigny+MK-677+Alzheimer+disease+progression+randomized+2008"}},{"outcome":"Adverse effects","grade":"B","grade_meaning":"probable, not settled","effect_size":"moderate","adverse":true,"human_studies":"Same RCTs","evidence":"Increased appetite, fluid retention and oedema, muscle pain, and rises in fasting glucose and insulin resistance are reported consistently, as with any sustained growth-hormone elevation. The trials were one to two years; there is no data beyond that.","references":[{"citation":"Nass R, Pezzoli SS, Oliveri MC, et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial.","where":"Ann Intern Med, 2008;149(9):601–611","url":"https://pubmed.ncbi.nlm.nih.gov/18981485/"},{"citation":"Sevigny JJ, Ryan JM, Van Dyck CH, et al. Growth hormone secretagogue MK-677: no clinical effect on AD progression in a randomized trial.","where":"Neurology, 2008","url":"https://pubmed.ncbi.nlm.nih.gov/?term=Sevigny+MK-677+Alzheimer+disease+progression+randomized+2008"}]}],"regions":[{"region":"European Union","status":"Unauthorised medicinal product","note":"No marketing authorisation in any member state. Supplying it for human use is an offence under national medicines law."},{"region":"United States","status":"Not approved","note":"Never approved; development discontinued. Sold as a 'research chemical'. Not a lawful dietary-supplement ingredient."},{"region":"United Kingdom","status":"Unlicensed medicine","note":"No MHRA licence; supply for human use is an offence."},{"region":"Australia","status":"Prescription-only / unapproved","note":"Not on the ARTG; imports are seized."},{"region":"Canada","status":"Not authorised","note":"No Drug Identification Number."},{"region":"Sport (WADA)","status":"Prohibited at all times","note":"Named on the Prohibited List among growth-hormone secretagogues, in and out of competition."}],"faq":[{"q":"Does MK-677 build muscle?","a":"In the one year-long trial, fat-free mass rose by about 1.1 kg in older adults against a loss on placebo. That is lean tissue, which includes water, and the trial did not measure strength. In young, trained people it has never been tested."},{"q":"Does MK-677 burn fat?","a":"No. Total fat and visceral fat did not change over a year, and limb fat rose. The appetite increase that comes with a ghrelin mimic works against fat loss."},{"q":"Is MK-677 a peptide?","a":"No — it is a small molecule designed to do what the ghrelin-mimicking peptides do, but by mouth. It is covered here because it is sold alongside them and acts on the same receptor."},{"q":"Is MK-677 legal?","a":"It is not an approved medicine anywhere and is prohibited in sport at all times. Rules on possession vary by country; selling it for human use is an offence in the EU and UK."}],"references":[{"cite":"Nass R, Pezzoli SS, Oliveri MC, et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial.","where":"Ann Intern Med, 2008;149(9):601–611","url":"https://pubmed.ncbi.nlm.nih.gov/18981485/","note":"65 adults aged 60–81; two years, primary analysis at one year."},{"cite":"Sevigny JJ, Ryan JM, Van Dyck CH, et al. Growth hormone secretagogue MK-677: no clinical effect on AD progression in a randomized trial.","where":"Neurology, 2008","url":"https://pubmed.ncbi.nlm.nih.gov/?term=Sevigny+MK-677+Alzheimer+disease+progression+randomized+2008","note":"563 patients; 12 months; negative on all four clinical measures."},{"cite":"World Anti-Doping Agency. The Prohibited List — S2: peptide hormones, growth factors, related substances and mimetics.","where":"WADA, current list","url":"https://www.wada-ama.org/en/prohibited-list","note":"Growth-hormone secretagogues, ibutamoren named."}],"last_reviewed":"2026-09-10","literature_searched_to":"2026-09-10","changelog":[{"date":"2026-09-10","note":"Initial publication. Grade B for lean mass on one 12-month RCT; fat loss and Alzheimer's carry high-certainty null results (effect none)."}],"license":"CC BY 4.0 — cite as “LYO Research” with a link.","methodology":"https://lyoresearch.com/methodology"}