MK-677 (ibutamoren): what the research shows
- By Reed Calder
- Last reviewed Nov 6, 2026
- 33 studies and official documents checked
In short
MK-677 (ibutamoren) is a lab-made chemical, not a peptide. It copies ghrelin, the hunger hormone, to make the body release more growth hormone, and it works as a pill. In a 1-year trial in healthy older adults it raised growth hormone and added 1.1 kg (2.4 lb) of lean mass, but strength didn’t change and blood sugar rose. It didn’t slow Alzheimer’s, and a hip-fracture trial was stopped early over heart failure. It isn’t FDA-approved, FDA’s advisers voted 13 to 1 against letting pharmacies compound it, and it’s banned in sport.
EvidenceCellAnimalHuman
MK-677 is sold as capsules and liquids for muscle, fat loss, sleep and “natural” growth hormone, often next to SARMs. Merck developed it in the 1990s, and trials in people ran for up to two years. A drug company is now testing it again, as LUM-201, in children who make too little growth hormone. This page covers what those trials found, its side effects, and where it stands legally.
Names and forms you’ll see
| Name | What it is | Studied in people? |
|---|---|---|
| MK-677, MK-0677 | Merck’s code names for the compound | Yes, trials from 1996 to 2018 |
| Ibutamoren | Its generic chemical name | Yes (same compound) |
| Ibutamoren mesylate | The salt form used in the trials and in the products proposed to the FDA (FDA, 2024) | Yes |
| L-163,191 | Its early lab code (Patchett et al., 1995) | Same compound |
| LUM-201 | The same compound, in development for children with growth hormone deficiency (Bright et al., 2022) | Yes, in children |
CAS numbers
A CAS number is a substance’s chemical registry number. Some “research” vials list it in place of a name. A different number usually means a different form, such as a salt, or a different substance.
Is MK-677 a peptide?
No. Peptides are chains of amino acids. MK-677 is a small synthetic molecule, formula C27H36N4O5S, with a molecular weight of 528.7 (PubChem). Merck designed it as a swallowable copy of the growth-hormone-releasing peptides, such as GHRP-6 (Patchett et al., 1995). Receptor researchers class it as a non-peptide (Holst et al., 2009).
You may read that it’s “peptide-like”. One end of the molecule is built from two amino-acid pieces, serine and a lab-made amino acid called Aib (FDA, 2024). The rest is a ring structure that isn’t made of amino acids.
Why it works as a pill
Growth hormone and most peptides are broken down in the gut, so they’re injected. MK-677 survives digestion and raises growth hormone when swallowed (Lee et al., 2018). It acts on the ghrelin receptor in the brain and pituitary gland, the same receptor as ipamorelin and GHRP-6 (Holst et al., 2009). In older adults, once-daily doses made the body’s own growth hormone pulses bigger without adding more of them (Chapman et al., 1996).
What has been studied
In people
- Lean mass in older adults, 1 year. In 65 healthy adults aged 60 to 81, 25 mg a day raised growth hormone and IGF-1 to young-adult levels. Fat-free mass rose 1.1 kg (2.4 lb) while it fell 0.5 kg (1.1 lb) on placebo. Belly fat didn’t change, limb fat rose, and strength and function didn’t improve (Nass et al., 2008).
- Obese young men, 2 months. In 24 men, fat-free mass rose and body fat didn’t change; a glucose tolerance test got worse (Svensson et al., 1998).
- Dieting. In 8 healthy people on a low-calorie diet, a week of MK-677 stopped the loss of body protein (Murphy et al., 1998).
- Sleep. In 8 young men, a week at 25 mg taken at bedtime raised deep sleep by about 50% and REM sleep by more than 20%; in 6 older adults, REM sleep rose by nearly 50% (Copinschi et al., 1997).
- Bone. In 292 women with osteoporosis, adding MK-677 to alendronate raised bone density at the top of the thigh bone (4.2% vs 2.5%) but not at the spine or whole hip (Murphy et al., 2001).
- Hip fracture, two trials. In 161 older adults, function didn’t improve significantly (Bach et al., 2004). In 123 more, gait speed improved but most other measures didn’t, and the trial was stopped early over heart failure in a few patients (Adunsky et al., 2011).
- Alzheimer’s disease. In 563 patients over 12 months, IGF-1 rose 73% but memory and daily function declined as fast as on placebo (Sevigny et al., 2008).
- Kidney dialysis. In 22 patients over 3 months, IGF-1 rose 65% more than on placebo; the study didn’t measure muscle or strength (Campbell et al., 2018).
- Children with growth hormone deficiency. In a 6-month trial, children on LUM-201 grew 6.8 to 8.2 cm (2.7 to 3.2 in) a year, depending on dose, against 10.6 cm (4.2 in) on injected growth hormone (NCT04614337). A placebo-controlled phase 3 trial started in May 2026 (NCT06948214).
- Fatty liver, a 12-person pilot. Over 6 months on 25 mg a day, with no placebo group, liver fat didn’t fall (average change +3.9 points, not significant), and 4 of 12 had high blood sugar (NCT05364684).
EvidenceCellAnimalHuman
In animals
- Dogs. Oral doses as low as 0.125 mg per kg raised growth hormone in beagles (Patchett et al., 1995).
- It stopped working in rats. In young rats, the growth hormone rise was gone after 6 weeks of daily doses, and the rats didn’t grow more (Lee et al., 2018). In people, IGF-1 stayed raised for 12 months (Sevigny et al., 2008).
- Alzheimer’s mice. In mice bred to develop amyloid plaques, it reduced plaque-related damage (Jeong et al., 2018). The trial in people with Alzheimer’s found no benefit (Sevigny et al., 2008).
EvidenceCellAnimalHuman
The usual claims, checked
| Claim | What the studies found |
|---|---|
| Builds muscle | Lean mass rose 1.1 kg (2.4 lb) in a year, but strength didn’t (Nass et al., 2008). No trial has studied young people who lift weights |
| Burns fat | Total and belly fat didn’t change in two trials (Nass et al., 2008; Svensson et al., 1998). Weight rose 2.7 kg (6.0 lb) vs 0.8 kg (1.8 lb) on placebo |
| Deeper sleep | In one small study of 14 people (Copinschi et al., 1997) |
| Stronger bones | Bone turnover rose; with alendronate, density rose at one site of four (Murphy et al., 2001) |
| Boosts your own growth hormone, so it’s safe | It raised growth hormone in every trial, and still caused high blood sugar and fluid retention (Nass et al., 2008) and a heart failure signal after hip fracture (Adunsky et al., 2011) |
| Makes you taller | Only studied in children with growth hormone deficiency, who grew less than on injected growth hormone (NCT04614337) |
What the studies used
| Study | Who | How given | Placebo group |
|---|---|---|---|
| Nass et al., 2008 | 65 healthy adults aged 60 to 81 | 25 mg by mouth once a day, 1 year (2 years exploratory) | Yes |
| Sevigny et al., 2008 | 563 people with Alzheimer’s | 25 mg once a day, 12 months | Yes |
| Adunsky et al., 2011 | 123 older adults after hip fracture | 25 mg once a day, up to 24 weeks | Yes |
| Copinschi et al., 1997 | 8 young men, 6 older adults | 2 to 25 mg at bedtime, 1 to 2 weeks | Yes, crossover |
| NCT04614337 | Children with growth hormone deficiency | LUM-201, 0.8, 1.6 or 3.2 mg per kg a day | No; compared with injected growth hormone |
The products proposed to the FDA for compounding were 10 mg and 25 mg capsules or tablets (FDA, 2024).
These are the studies’ methods, not a dose for anyone to use. Most adult trials used 25 mg once a day in older or sick people; no dose comes from a study in healthy young adults.
Side effects and safety
- Higher blood sugar. Fasting glucose rose and insulin sensitivity fell over a year (Nass et al., 2008). In older adults, fasting glucose went from 5.4 to 6.8 mmol/L (97 to 123 mg/dL) in 4 weeks at 25 mg (Chapman et al., 1996).
- Hunger, swelling and muscle pain. The most common side effects were more appetite, which faded within a few months, and mild leg swelling and muscle pain (Nass et al., 2008).
- Heart failure after hip fracture. A trial in older adults was stopped early over heart failure (Adunsky et al., 2011). The FDA lists this as a significant safety risk (FDA, 2026).
- Hormone changes. Cortisol rose (Nass et al., 2008) and prolactin rose 23% (Chapman et al., 1996).
- The FDA’s other concerns. Its 2024 review also lists liver enzyme rises in trials, low blood pressure in rats, possible addiction through the ghrelin system, and the risks of raising IGF-1 for years: higher IGF-1 levels have been linked to cancer risk (FDA, 2024).
- Case reports. A man in his 30s developed liver inflammation after 2 months of MK-677, which cleared after he stopped (Cobani et al., 2025).
- Unstudied groups. No published study covers pregnancy, breastfeeding, healthy children or use beyond 2 years.
What’s in the bottle
Products sold online often aren’t what the label says. Of 44 products sold as SARMs, 17 contained another unapproved drug, ibutamoren among them (Van Wagoner et al., 2017). A man who took three gym supplements containing MK-677, a SARM and cardarine developed breast growth and low testosterone; lab tests also found undeclared testosterone, estradiol and growth hormone in the products (Chong et al., 2024).
Side effects people report from online products aren’t covered here; they come from users, not studies.
Legal and approval status
- Not FDA-approved, and not part of any approved drug (FDA, 2024).
- Pharmacies can’t compound it. The FDA lists ibutamoren mesylate among substances that may present significant safety risks in compounding (FDA, 2026). Its 2024 review found it unproven for every use nominated, and on October 29, 2024, its advisory committee voted 13 to 1 against allowing it (FDA committee minutes, 2024).
- Not covered by the 2026 HHS policy. The temporary HHS policy of October 2026 covers six peptides; MK-677 isn’t one of them (Reuters, 2026).
- Not a legal supplement. The FDA has concluded that ibutamoren can’t be sold as a dietary supplement. In December 2025 it warned a company whose children’s “growth” supplements contained undeclared ibutamoren in FDA lab tests (FDA warning letter, 2025).
- Back in drug trials. As LUM-201, it’s in a phase 3 trial in children with growth hormone deficiency, with its main results due after December 2027 (NCT06948214), and a trial with oral semaglutide in older adults with obesity is planned (NCT07754045).
- Banned in sport and the military. The World Anti-Doping Agency’s 2026 list names ibutamoren (MK-677) as a growth hormone secretagogue, banned at all times (WADA, 2026). It’s also on the U.S. Department of Defense prohibited supplement ingredients list (Operation Supplement Safety).
- “Research use only” products aren’t approved for use in people.
What to look for if you research it
We don’t name or link sellers. These checks come from the FDA review and the published studies:
- Molecular weight on the certificate. It should read 528.7 for ibutamoren (PubChem) or 624.8 for ibutamoren mesylate, the salt form (PubChem).
- Chiral purity and impurities. MK-677 has a mirror-image form. The FDA noted that the certificates sent with the nominations didn’t report chiral purity, impurities or leftover solvents (FDA, 2024).
- Supplements and SARM blends. Products in these categories have contained drugs that weren’t on the label (Van Wagoner et al., 2017).
Our guide to what to look for explains what each test on a lab report proves and which routes are legal; how to read a peptide study explains how to judge the studies sellers cite.
What’s still unknown
- Whether the lean mass it adds makes anyone stronger or healthier.
- What it does in healthy young adults; the trials were in older or sick people.
- Whether years of raised IGF-1 change cancer or heart risk.
- Whether LUM-201 works well enough in children to be approved.
Retracted and flagged studies
A retracted study has been pulled by its journal, usually for serious errors or misconduct, and its results shouldn’t be relied on. A withdrawn paper was pulled, often before final publication. An expression of concern means the journal has flagged a problem it is still looking into.
We check every study this page cites against PubMed and the Retraction Watch database, and search both for flagged studies that mention MK-677. We recheck every month. Last checked Nov 11, 2026.
We found no retracted, withdrawn or flagged studies that mention MK-677.
Studies this page relies on
| Study | Published in | Status |
|---|---|---|
| Patchett et al., 1995 | Proc Natl Acad Sci U S A | No retraction or concern |
| Chapman et al., 1996 | J Clin Endocrinol Metab | No retraction or concern |
| Copinschi et al., 1997 | Neuroendocrinology | No retraction or concern |
| Murphy et al., 1998 | J Clin Endocrinol Metab | No retraction or concern |
| Svensson et al., 1998 | J Clin Endocrinol Metab | No retraction or concern |
| Murphy et al., 2001 | J Clin Endocrinol Metab | No retraction or concern |
| Bach et al., 2004 | J Am Geriatr Soc | No retraction or concern |
| Holst et al., 2009 | Mol Pharmacol | No retraction or concern |
| Nass et al., 2008 | Ann Intern Med | No retraction or concern |
| Sevigny et al., 2008 | Neurology | No retraction or concern |
| Adunsky et al., 2011 | Arch Gerontol Geriatr | No retraction or concern |
| Campbell et al., 2018 | Nephrol Dial Transplant | No retraction or concern |
| Van Wagoner et al., 2017 | JAMA | No retraction or concern |
| Jeong et al., 2018 | Int J Mol Sci | No retraction or concern |
| Lee et al., 2018 | Yonsei Med J | No retraction or concern |
| Bright and Thorner, 2022 | Horm Res Paediatr | No retraction or concern |
| Chong et al., 2024 | JCEM Case Rep | No retraction or concern |
| Cobani et al., 2025 | BMJ Case Rep | No retraction or concern |
Bring your questions to other researchers
Our forum opens once 100 researchers join the waitlist. Members post studies, ask what they actually found, and answer with sources.
Questions
Is MK-677 a peptide?
No. It’s a lab-made small molecule that copies a peptide hormone, ghrelin, and part of its structure comes from two amino acids (FDA, 2024). Researchers class it as a non-peptide (Holst et al., 2009).
Is MK-677 a SARM or a steroid?
Neither. It acts on the ghrelin receptor, not the androgen receptor that SARMs and steroids act on (Holst et al., 2009). It’s often sold alongside SARMs, and some SARM products contain it (Van Wagoner et al., 2017).
What does MK-677 do?
It raises growth hormone and IGF-1. In a 1-year trial in older adults it added lean mass and raised blood sugar, with no change in strength (Nass et al., 2008).
Does MK-677 build muscle?
It added 1.1 kg (2.4 lb) of fat-free mass in a year in older adults, but strength and function didn’t improve (Nass et al., 2008). No published study has looked at young people who train.
What are the side effects of MK-677?
In trials: more hunger, higher blood sugar, mild swelling and muscle pain (Nass et al., 2008), and heart failure in a hip-fracture trial that was stopped early (Adunsky et al., 2011).
What is the MK-677 dosage?
No dose comes from a study for anyone to use. Most adult trials used 25 mg once a day in older or sick people (Nass et al., 2008; Sevigny et al., 2008).
Does MK-677 lower testosterone?
We found no trial that measured it. In one case report, a man taking supplements with MK-677 and other drugs had low testosterone that recovered after he stopped (Chong et al., 2024).
Does MK-677 cause hair loss?
We found no published study linking MK-677 to hair loss, and none that measured hair.
Can MK-677 make you taller?
It’s only been studied for height in children with growth hormone deficiency, who grew 6.8 to 8.2 cm (2.7 to 3.2 in) a year on it, less than on injected growth hormone (NCT04614337). No study covers adults.
When is the best time to take MK-677?
No study compared times of day. The sleep study gave it at bedtime (Copinschi et al., 1997).
Does MK-677 stop working over time?
In rats, its growth hormone effect was gone after 6 weeks (Lee et al., 2018). In people, IGF-1 stayed 73% higher after 12 months (Sevigny et al., 2008).
Is MK-677 legal?
It isn’t FDA-approved, can’t be sold as a supplement, and pharmacies can’t compound it; the FDA’s advisers voted 13 to 1 against it (FDA, 2024). It’s banned in sport at all times (WADA, 2026).
MK-677 or ipamorelin?
Both act on the ghrelin receptor. MK-677 is swallowed and has trials in people lasting up to two years; ipamorelin is an injected peptide with its own, different evidence.
Sources
- Patchett AA, et al. Design and biological activities of L-163,191 (MK-0677): a potent, orally active growth hormone secretagogue. Proc Natl Acad Sci U S A. 1995;92(15):7001-5. PubMed 7624358
- Holst B, et al. Overlapping binding site for the endogenous agonist, small-molecule agonists, and ago-allosteric modulators on the ghrelin receptor. Mol Pharmacol. 2009;75(1):44-59. PubMed 18923064
- Chapman IM, et al. Stimulation of the growth hormone (GH)-insulin-like growth factor I axis by daily oral administration of a GH secretogogue (MK-677) in healthy elderly subjects. J Clin Endocrinol Metab. 1996;81(12):4249-57. PubMed 8954023
- 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. PubMed 18981485
- Svensson J, et al. Two-month treatment of obese subjects with the oral growth hormone (GH) secretagogue MK-677 increases GH secretion, fat-free mass, and energy expenditure. J Clin Endocrinol Metab. 1998;83(2):362-9. PubMed 9467542
- Murphy MG, et al. MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolism. J Clin Endocrinol Metab. 1998;83(2):320-5. PubMed 9467534
- Copinschi G, et al. Prolonged oral treatment with MK-677, a novel growth hormone secretagogue, improves sleep quality in man. Neuroendocrinology. 1997;66(4):278-86. PubMed 9349662
- Murphy MG, et al. Effect of alendronate and MK-677 (a growth hormone secretagogue), individually and in combination, on markers of bone turnover and bone mineral density in postmenopausal osteoporotic women. J Clin Endocrinol Metab. 2001;86(3):1116-25. PubMed 11238495
- 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. PubMed 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. PubMed 21067829
- 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. PubMed 19015485
- Campbell GA, et al. Oral ghrelin receptor agonist MK-0677 increases serum insulin-like growth factor 1 in hemodialysis patients: a randomized blinded study. Nephrol Dial Transplant. 2018;33(3):523-530. PubMed 28340044
- Bright GM, et al. A GH Secretagogue Receptor Agonist (LUM-201) Elicits Greater GH Responses than Standard GH Secretagogues in Subjects of a Pediatric GH Deficiency Trial. Horm Res Paediatr. 2022;95(1):76-81. PubMed 35354138
- Lee J, et al. Effect of the Orally Active Growth Hormone Secretagogue MK-677 on Somatic Growth in Rats. Yonsei Med J. 2018;59(10):1174-1180. PubMed 30450851
- Jeong YO, et al. MK-0677, a Ghrelin Agonist, Alleviates Amyloid Beta-Related Pathology in 5XFAD Mice, an Animal Model of Alzheimer’s Disease. Int J Mol Sci. 2018;19(6). PubMed 29912176
- Cobani E, et al. Hepatotoxicity induced by MK-677. BMJ Case Rep. 2025;18(7):e265728. PubMed 40675653
- Chong S, et al. Reversible Gynecomastia and Hypogonadism Due to Usage of Commercial Performance-Enhancing Supplement Use. JCEM Case Rep. 2024;2(8):luae148. PubMed 39145153
- 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. PubMed 29183075
- ClinicalTrials.gov. Phase 2 Study of LUM-201 in Children With Growth Hormone Deficiency (OraGrowtH210 Trial) (NCT04614337). Posted results. Record
- ClinicalTrials.gov. Phase 3 Study of LUM-201 in Children With Growth Hormone Deficiency (NCT06948214). Record
- ClinicalTrials.gov. Evaluating the Efficacy and Safety of LUM-201 Plus Semaglutide Versus Semaglutide Plus Placebo in Older Obese Adults (NCT07754045). Record
- ClinicalTrials.gov. The Impact of Ibutamoren on Nonalcoholic Fatty Liver Disease (NCT05364684). Posted results. Record
- U.S. Food and Drug Administration. FDA Evaluation of Ibutamoren Mesylate. Pharmacy Compounding Advisory Committee briefing document, October 29, 2024 (memo dated July 3, 2024). FDA document
- U.S. Food and Drug Administration. Final Summary Minutes of the Pharmacy Compounding Advisory Committee Meeting, October 29, 2024. FDA document
- U.S. Food and Drug Administration. Safety risks associated with certain bulk drug substances nominated for use in compounding. Content current as of April 22, 2026. FDA page
- U.S. Food and Drug Administration. Warning letter 718252, December 19, 2025. FDA letter
- PubChem. Ibutamoren (CID 178024). PubChem
- PubChem. Ibutamoren mesylate (CID 6450830). PubChem
- Operation Supplement Safety (U.S. Department of Defense). Performance Enhancing Substance: MK-677 (Ibutamoren). Article
- World Anti-Doping Agency. 2026 Prohibited List (S2.2.4, growth hormone secretagogues). WADA document
- Reuters. U.S. health department to allow temporary sale of some unapproved peptides. October 28, 2026. Article
- U.S. Food and Drug Administration. Global Substance Registration System: Ibutamoren (UNII GJ0EGN38UL). GSRS
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Last reviewed Nov 6, 2026. Approval and compounding status change often; we recheck this page when they do. Nothing here is medical advice; see our medical disclaimer. Found a mistake? Email editors@peptideresearchstudy.com.