MK-677 (Ibutamoren): The Complete Guide to the Oral Secretagogue That Never Became a Drug

What MK-677 is, and why it is not a peptide

MK-677, also called ibutamoren mesylate, MK-0677 and in its latest trials LUM-201, is a spiroindoline sulfonamide: a compact drug-like molecule, not a chain of amino acids. It is sold beside peptides because it does what the growth hormone-releasing peptides GHRP-6 and ipamorelin do. It activates the ghrelin receptor on the pituitary, which releases growth hormone and, downstream, raises IGF-1.

What set it apart was the route. In beagles, single oral doses raised peak growth hormone 5.3- to 15.8-fold, a 1 mg/kg dose kept it raised for up to 360 minutes, and IGF-1 rose by 30% at eight hours; cortisol rose 2.4-fold ¹. No peptide in the family could be swallowed. The half-life figures that circulate for it (often "5 to 6 hours") come from no study in our evidence set.

What it does in the short term

Growth hormone and IGF-1. In 32 healthy adults aged 64 to 81, 25 mg a day raised 24-hour growth hormone by 97% after two weeks, through taller pulses, and lifted IGF-1 from 141 to 265 µg/L at four weeks, into the young-adult range. Fasting glucose rose from 5.4 to 6.8 mmol/L; prolactin rose 23% within the normal range and cortisol did not change ². In nine young men, a week of 5 or 25 mg at bedtime raised pulse frequency and IGF-1 with little change in cortisol ³.

Protein, body composition and bone. In eight volunteers on a calorie-restricted diet, a week of 25 mg turned a nitrogen loss of 1.48 g a day into a gain of 0.31 ⁴. In 24 obese men, eight weeks raised IGF-1 about 40% and increased fat-free mass without changing total or visceral fat, but glucose tolerance tests worsened at two and eight weeks ⁵. Markers of both bone formation and bone breakdown rose in the same men ⁶ and in 187 older adults across three trials ⁷.

Sleep. In eight young adults, 25 mg at bedtime for a week lengthened stage 4 sleep by about 50% and REM sleep by more than 20%; in six adults aged 65 to 71, two weeks increased REM sleep by nearly 50% ⁸. It is one small study.

The long trials, where it stalled

Healthy older adults. The most-cited trial gave 65 adults aged 60 to 81 either 25 mg or placebo for two years. Growth hormone and IGF-1 rose to young-adult levels. Fat-free mass rose 1.1 kg on MK-677 and fell 0.5 kg on placebo, but abdominal visceral fat and total fat did not change, limb fat rose more (1.1 against 0.24 kg), body weight rose 2.7 kg against 0.8, fasting glucose rose 0.3 mmol/L and insulin sensitivity fell ⁹.

Alzheimer's disease. In 563 people with mild to moderate Alzheimer's disease, a year of 25 mg a day raised IGF-1 by 60.1% at six weeks and 72.9% at a year, and made no difference on any of four measures of cognition, function and global change ¹⁰. In mice bred to develop Alzheimer's pathology, it increased new neurons but did not prevent amyloid, synapse loss or cognitive decline, and at 3 mg/kg it increased deaths ¹¹.

Hip fracture. In 161 previously mobile patients aged 65 or older, six months of treatment raised IGF-1 by 84% (17% on placebo) with no significant difference in functional performance or disability ¹². A second trial in 123 patients found modestly better gait speed and fewer falls but no improvement in stair-climbing power or most other measures, and was terminated early because of a congestive heart failure signal in a limited number of patients; the authors called its safety profile unfavourable in this population ¹³.

Bone and kidneys. In 292 women with postmenopausal osteoporosis, MK-677 with alendronate raised femoral-neck bone density more than alendronate alone (4.2% against 2.5%), but not at other sites ¹⁴. In 22 hemodialysis patients, three months raised IGF-1 1.76-fold with no serious adverse effects attributed to it ¹⁵. Neither result led to an approval.

Does the effect fade?

Partly. In beagles given daily doses, the growth hormone response to each dose fell by 41 to 77% over two weeks, but IGF-1 stayed raised with daily (not alternate-day) dosing ¹⁶. In people on the diet study, the growth hormone peak fell from 55.9 µg/L after the first dose to 22.6 after a week, while IGF-1 rose ⁴. In the two-year trial IGF-1 stayed at young-adult levels ⁹. So the claim that it causes no tolerance is wrong about growth hormone and closer to right about IGF-1.

Side effects and safety

• Glucose. Fasting glucose rose in older adults (5.4 to 6.8 mmol/L at 25 mg) ² and in the two-year trial, where insulin sensitivity also fell ⁹; glucose tolerance worsened in obese men ⁵.
• Weight, appetite and fluid. Weight and limb fat rose in the two-year trial ⁹. Oedema, increased appetite and muscle pain are its known side effects, as a 2025 case report summarises ¹⁷.
• Heart failure. A trial in older hip-fracture patients was stopped early over a congestive heart failure signal ¹³.
• Liver. A man in his early 30s developed raised liver enzymes after two months of MK-677 bought as a performance supplement, and recovered after stopping ¹⁷.
• Stacks. A 25-year-old taking MK-677 with the SARM LGD-4033 for five weeks gained lean mass but saw HDL fall 36%, ALT rise 205% and testosterone fall 62%; with two drugs in one person, the effects cannot be assigned to MK-677 ¹⁸.

What these add up to is a drug whose effects on laboratory markers are real and whose effects on health outcomes, in the populations tested, were small or absent, with metabolic and cardiac costs in older people.

Where it stands with regulators

Never approved. No approval followed the adult trials. The molecule later returned as LUM-201 for children with growth hormone deficiency: a 2021 analysis of a completed randomised trial in 68 untreated prepubertal children found that a baseline IGF-1 above 30 ng/mL and a growth hormone peak of at least 5 ng/mL after one dose picked out the children who grew better on it; the rest did better on injected growth hormone ¹⁹. Earlier, a week of treatment in 18 children with deficiency had raised growth hormone peaks modestly and with wide variation ²⁰.

Compounding. On October 29, 2024, FDA's Pharmacy Compounding Advisory Committee voted 13 to 1 against adding ibutamoren mesylate to the 503A bulks list ²¹. FDA lists it in Category 2 under both 503A and 503B, as a substance that may present significant safety risks ²².

Supplements. In a warning letter dated December 19, 2025, FDA told a company that products marketed for children's growth contained undeclared ibutamoren mesylate, and that ibutamoren is excluded from the definition of a dietary supplement under section 201(ff)(3)(B)(ii) of the FD&C Act ²³. It cannot lawfully be sold as a supplement in the US, whatever a label says.

Sport. WADA's 2026 Prohibited List names ibutamoren under S2.2.4, prohibited at all times, and the 2027 List keeps it there ^{24 25}. It is detectable in hair: four weeks after a single 10 mg dose a volunteer's hair held 1.3 pg/mg, and hair from a person who took sixty capsules over 90 days held 224 pg/mg ²⁶.

Claims you will see, checked

• "MK-677 is a peptide." It is a small molecule, a spiroindoline sulfonamide, taken by mouth ¹.
• "It builds muscle." Fat-free mass rose about 1.1 kg over a year in healthy older adults, with more weight, limb fat and glucose ⁹. In hip-fracture recovery, most functional measures did not improve ^{12 13}.
• "It has no side effects." The trials recorded higher glucose, lower insulin sensitivity and weight gain ⁹, and one was stopped over heart failure ¹³.
• "It never loses effect." The growth hormone response fades with daily dosing; IGF-1 stays raised ^{16 4}.
• "It is a legal supplement." FDA says ibutamoren is excluded from the definition of a dietary supplement ²³.

Dosing: what was studied and what circulates

The trial doses overlap with what circulates, but the trials enrolled older adults and patients under medical supervision, measured glucose and heart function, and still found costs. MK-677 is taken by mouth, so there is nothing to reconstitute; products sold online are unapproved and, according to FDA, cannot be sold as supplements.

How it compares

Frequently asked questions

Is MK-677 a peptide?

No. It is a small molecule, a spiroindoline sulfonamide, that acts on the same ghrelin receptor as the growth hormone-releasing peptides and is taken by mouth.

Does MK-677 build muscle?

In a two-year trial in 65 healthy adults aged 60 to 81, 25 mg a day raised fat-free mass by about 1.1 kg against a 0.5 kg fall on placebo, but it also raised weight, limb fat and fasting glucose and lowered insulin sensitivity. In hip-fracture patients most functional measures did not improve.

What are MK-677's side effects?

In trials: higher fasting glucose, lower insulin sensitivity, weight gain and more limb fat; oedema, increased appetite and muscle pain are also reported. A hip-fracture trial was stopped early over a congestive heart failure signal, and a 2025 case report describes liver injury.

Is MK-677 legal to buy as a supplement?

No. In a December 19, 2025 warning letter, FDA stated that ibutamoren is excluded from the definition of a dietary supplement, and it is not approved as a drug. FDA's advisers voted 13 to 1 against allowing it in pharmacy compounding in 2024 (as of September 28, 2026).

Is MK-677 banned in sport?

Yes. WADA's 2026 and 2027 Prohibited Lists name ibutamoren under S2.2.4, prohibited at all times, and it can be detected in hair weeks after use.

Related on Grey Peptides

• MK-677 encyclopedia entry
• Ipamorelin encyclopedia entry
• GHRP-6 encyclopedia entry
• Ipamorelin: the complete guide
• Regulatory tracker

Sources

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2. Chapman, I. M. et al. (1996). 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, 81(12), 4249-57. PMID: 8954023
3. Copinschi, G. et al. (1996). Effects of a 7-day treatment with a novel, orally active, growth hormone (GH) secretagogue, MK-677, on 24-hour GH profiles, insulin-like growth factor I, and adrenocortical function in normal young men. J Clin Endocrinol Metab, 81(8), 2776-82. PMID: 8768828
4. Murphy, M. G. et al. (1998). MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolism. J Clin Endocrinol Metab, 83(2), 320-5. PMID: 9467534
5. Svensson, J. et al. (1998). 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, 83(2), 362-9. PMID: 9467542
6. Svensson, J. et al. (1998). Treatment with the oral growth hormone secretagogue MK-677 increases markers of bone formation and bone resorption in obese young males. J Bone Miner Res, 13(7), 1158-66. PMID: 9661080
7. Murphy, M. G. et al. (1999). Oral administration of the growth hormone secretagogue MK-677 increases markers of bone turnover in healthy and functionally impaired elderly adults. The MK-677 Study Group. J Bone Miner Res, 14(7), 1182-8. PMID: 10404019
8. Copinschi, G. et al. (1997). Prolonged oral treatment with MK-677, a novel growth hormone secretagogue, improves sleep quality in man. Neuroendocrinology, 66(4), 278-86. PMID: 9349662
9. Nass, R. et al. (2008). Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial. Ann Intern Med, 149(9), 601-11. PMID: 18981485
10. Sevigny, J. J. et al. (2008). Growth hormone secretagogue MK-677: no clinical effect on AD progression in a randomized trial. Neurology, 71(21), 1702-8. PMID: 19015485
11. Tian, J. et al. (2019). MK0677, a Ghrelin Mimetic, Improves Neurogenesis but Fails to Prevent Hippocampal Lesions in a Mouse Model of Alzheimer's Disease Pathology. J Alzheimers Dis, 72(2), 467-478. PMID: 31594237
12. Bach, M. A. et al. (2004). The effects of MK-0677, an oral growth hormone secretagogue, in patients with hip fracture. J Am Geriatr Soc, 52(4), 516-23. PMID: 15066065
13. Adunsky, A. et al. (2011). MK-0677 (ibutamoren mesylate) for the treatment of patients recovering from hip fracture: a multicenter, randomized, placebo-controlled phase IIb study. Arch Gerontol Geriatr, 53(2), 183-9. PMID: 21067829
14. Murphy, M. G. et al. (2001). 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, 86(3), 1116-25. PMID: 11238495
15. Campbell, G. A. et al. (2018). Oral ghrelin receptor agonist MK-0677 increases serum insulin-like growth factor 1 in hemodialysis patients: a randomized blinded study. Nephrol Dial Transplant, 33(3), 523-530. PMID: 28340044
16. Hickey, G. J. et al. (1997). Repeat administration of the GH secretagogue MK-0677 increases and maintains elevated IGF-I levels in beagles. J Endocrinol, 152(2), 183-92. PMID: 9071975
17. Cobani, E. et al. (2025). Hepatotoxicity induced by MK-677. BMJ Case Rep, 18(7). PMID: 40675653
18. Cardaci, T. D. et al. (2022). LGD-4033 and MK-677 use impacts body composition, circulating biomarkers, and skeletal muscle androgenic hormone and receptor content: A case report. Exp Physiol, 107(12), 1467-1476. PMID: 36303408
19. Bright, G. M. et al. (2021). Development of a Predictive Enrichment Marker for the Oral GH Secretagogue LUM-201 in Pediatric Growth Hormone Deficiency. J Endocr Soc, 5(6), bvab030. PMID: 33982679
20. Codner, E. et al. (2001). Effects of oral administration of ibutamoren mesylate, a nonpeptide growth hormone secretagogue, on the growth hormone-insulin-like growth factor I axis in growth hormone-deficient children. Clin Pharmacol Ther, 70(1), 91-8. PMID: 11452249
21. U.S. Food and Drug Administration. Pharmacy Compounding Advisory Committee meeting, October 29, 2024: summary minutes, Section 503A Bulk Drug Substances List, ibutamoren mesylate (vote: 1 yes, 13 no).
22. U.S. Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (current as of April 22, 2026). FDA Category 2 page
23. U.S. Food and Drug Administration. Warning letter to AgeBox Inc (MARCS-CMS 718252), December 19, 2025: undeclared ibutamoren mesylate in iKids-Growth products; ibutamoren excluded from the definition of a dietary supplement under FD&C Act section 201(ff)(3)(B)(ii).
24. World Anti-Doping Agency. The 2026 Prohibited List, section S2.2.4 (read September 27, 2026). WADA 2026 List
25. World Anti-Doping Agency. The 2027 Prohibited List, in force January 1, 2027 (read September 27, 2026). WADA 2027 List
26. Kintz, P. & Gheddar, L. (2026). Knowing the minimal detectable dose can facilitate the interpretation of a hair test result: II. Case example with ibutamoren (MK-677), a growth hormone secretagogue. Clin Chim Acta, 578, 120578. PMID: 40882886

This article is for education. It is not medical or legal advice, and it is not a guide to buying or using any compound. MK-677 is not approved as a medicine anywhere, cannot be sold as a US dietary supplement, and is prohibited in sport.