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MK-677: what the research shows, and what it doesn’t

By Pinnacle Pulse Editorial Team · Status as of 16 October 2026 · Next scheduled update: 14 January 2027

Short answer: MK-677, also called ibutamoren, is not a peptide. It is a small molecule taken by mouth that mimics ghrelin and raises growth hormone. It was tested in older adults, hip-fracture patients and people with Alzheimer’s disease. Lean mass and IGF-1 went up, but function and memory did not improve. One trial was stopped over heart failure.

What MK-677 is

Forums and online shops tend to file it with the peptides. It isn’t one. MK-677 is a small non-peptide molecule that survives the stomach, and that was the point of making it. Peptides like GHRP-6 and ipamorelin act on the same ghrelin receptor but have to be injected. MK-677 was developed at Merck as something people could swallow.

The generic name is ibutamoren mesylate. MK-677 and MK-0677 are the same compound under its company code. It is also sometimes sold as a SARM, which it isn’t either. SARMs act on the androgen receptor. MK-677 works through the growth hormone axis.

It has never been approved as a medicine in the EU or the US. Read the trials below and it’s not hard to see why.

What has been studied

Healthy older adults: lean mass, not strength

The best-known trial ran at the University of Virginia and was published in the Annals of Internal Medicine in 2008. Sixty-five healthy adults aged 60 to 81 took MK-677 or placebo daily for up to two years, under double-blind conditions.

Growth hormone and IGF-1 climbed to young-adult levels. Fat-free mass rose on MK-677 and dipped a little on placebo. Belly fat stayed put; limb fat went up more in the MK-677 group. And then comes the sentence people tend to leave out: The extra fat-free mass “did not result in changes in strength or function”. Fasting blood sugar rose and insulin sensitivity fell. Cortisol went up. People reported more appetite, which faded after a few months, plus mild swelling in the legs and muscle pain. The authors themselves said the study was too small and too short to judge function.

Alzheimer’s disease: no effect

Merck Research Laboratories ran a 12-month double-blind trial in 563 patients with mild to moderate Alzheimer’s disease, published in Neurology in 2008. The idea came from animal work suggesting IGF-1 helps clear amyloid from the brain. IGF-1 in patients’ blood rose substantially. On every cognitive and daily-function scale, there was no difference from placebo. The title of the paper says it plainly: “no clinical effect on AD progression”.

Hip fracture: a safety signal

Older people recovering from a broken hip were the subject of two more trials. In the first (2004; 161 patients, 13 centres in Europe and North America), IGF-1 went up, and the function tests showed nothing statistically significant.

The second, a phase IIb study with 123 patients published in 2011, found an improvement in gait speed but not in most other measures of physical function. It was stopped early because of a safety signal of congestive heart failure in a small number of patients. The authors’ conclusion was that MK-677 “has an unfavorable safety profile in this patient population”. FDA cites this trial in its own safety assessment.

On the gray market

In 2017 a study in JAMA analysed 44 products sold online as SARMs. Seventeen contained another unapproved drug, ibutamoren among them. Eleven held substances that weren’t on the label at all.

What the research does not show

Yes, growth hormone and IGF-1 go up. Every trial agrees on that. But in older adults, in Alzheimer's patients and in people with broken hips, the higher numbers didn't turn into better strength, function, memory or recovery.

Nor do they show it’s safe to take for years outside a study. If anything the signals run the other way. Blood sugar crept up, insulin sensitivity dropped, cortisol rose, legs swelled, and in frail patients there was a heart failure signal bad enough to halt a trial.

Young, healthy people taking it for the gym or for looks? We couldn’t find a single published trial in that group.

Status as of 16 October 2026. EU and US: not an authorized medicine (no entry in EMA’s medicines data or in Drugs@FDA). FDA has placed ibutamoren mesylate in category 2 for compounding under both 503A (since 29 September 2023) and 503B (since 29 December 2022), citing the congestive heart failure signal. WADA: the 2027 Prohibited List names ibutamoren (MK-677) under S2.2.4 (growth hormone secretagogues), prohibited at all times.

FAQ

Is MK-677 a peptide or a SARM?

Neither. It is a small, non-peptide molecule that is active when taken by mouth and mimics the hormone ghrelin. SARMs act on androgen receptors, which MK-677 does not.

What did the clinical trials of MK-677 find?

In healthy older adults it increased fat-free mass but not strength or function. In Alzheimer’s disease it had no effect on progression. In hip-fracture patients most function measures did not improve, and one trial was stopped early for a heart failure signal.

What side effects were reported in trials?

Increased appetite, mild leg swelling, muscle pain, higher fasting blood sugar, lower insulin sensitivity and higher cortisol in older adults. In one hip-fracture trial, a signal of congestive heart failure.

Sources

  • Nass R, et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial. Ann Intern Med. 2008;149(9):601-11. PMID 18981485
  • Sevigny JJ, et al. Growth hormone secretagogue MK-677: no clinical effect on AD progression in a randomized trial. Neurology. 2008;71(21):1702-8. PMID 19015485
  • Bach MA, et al. The effects of MK-0677, an oral growth hormone secretagogue, in patients with hip fracture. J Am Geriatr Soc. 2004;52(4):516-23. PMID 15066065
  • Adunsky A, et al. MK-0677 (ibutamoren mesylate) for the treatment of patients recovering from hip fracture: a multicenter, randomized, placebo-controlled phase IIb study. Arch Gerontol Geriatr. 2011;53(2):183-9. PMID 21067829
  • Van Wagoner RM, et al. Chemical composition and labeling of substances marketed as selective androgen receptor modulators and sold via the internet. JAMA. 2017;318(20):2004-2010. PMID 29183075
  • PubMed search “(MK-677 OR MK-0677 OR ibutamoren) AND randomized controlled trial[pt]”, run 16 October 2026 via NCBI E-utilities: 19 records.
  • FDA. Certain bulk drug substances for use in compounding that may present significant safety risks (content current as of 22 April 2026). fda.gov
  • WADA. 2027 Prohibited List, class S2.2.4. wada-ama.org
  • EMA. Download medicine data: table of all medicines assessed by EMA (Excel), checked 16 October 2026. ema.europa.eu
  • FDA. Drugs@FDA, database of FDA-approved drugs, checked 16 October 2026. accessdata.fda.gov

Facts last checked: 16 October 2026.

About this article

Written by: the Pinnacle Pulse Editorial Team, the people who make the Pinnacle Pulse app. We work only from primary sources such as regulators, legal texts, trial registries and PubMed, and we remove claims we can’t check against one.

This article has not been reviewed by a physician. It is general information, not medical advice.

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Change log

  • 16 October 2026: First published.

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This article is for general information only. It is not medical advice and does not recommend the use of any substance. Decisions about medicines belong with a qualified healthcare professional.