MK-677 vs Ipamorelin

Side by side

MK-677 Medium, also called ibutamoren, and ipamorelin Medium aim at the same target: the ghrelin receptor, which triggers growth hormone release from the pituitary. The difference is chemical. Ipamorelin is a five-amino-acid peptide that has to be injected; MK-677 is a small molecule designed to work as a pill ¹. Our guide to what makes a peptide a peptide explains why that matters. The table is read from our encyclopedia entries.

MK-677 in people

MK-677 was developed by Merck and tested extensively in the 1990s and 2000s. In healthy adults aged 64 to 81, the highest dose tested raised 24-hour growth hormone by 97% and IGF-1 into the young-adult range, but fasting glucose rose too ². In obese men given it for eight weeks, IGF-1 rose about 40% and lean mass increased, but total and visceral fat did not change, and glucose tolerance worsened ³. It lengthened deep sleep in young adults ⁴.

The larger trials were disappointing. In older people recovering from hip fracture, IGF-1 rose but functional performance did not improve significantly over six months ⁵, and in a later report of 123 patients gait speed improved modestly while other measures did not; that trial was stopped early over a congestive heart failure signal, according to our entry ^{6 1}. In a 12-month trial in people with mild to moderate Alzheimer's disease, IGF-1 rose by about 73% but there was no difference in cognition or global function ⁷. MK-677 reliably raises IGF-1; it has not shown that this helps.

Ipamorelin in people

Ipamorelin's human record is much shorter. In 40 healthy men given single intravenous infusions at five doses, its kinetics were proportional to dose with a terminal half-life of about two hours ⁸. Its one efficacy trial, a double-blind phase 2 study in 114 adults recovering from bowel resection, found no significant benefit on the return of bowel function ⁹. In animals it released growth hormone without raising ACTH or cortisol, unlike older peptides in its family ¹⁰, but nothing comparable to MK-677's long trials exists.

Side effects and safety signals

The safety picture differs mainly because MK-677 has been studied long enough to show problems. Its trials recorded rises in fasting glucose and impaired glucose tolerance ^{2 3}, and the hip-fracture trial's heart-failure signal is part of its record ¹. Case reports from people using it as a performance supplement describe raised liver enzymes that resolved after stopping ¹¹, and, combined with another drug in a young man, falls in bone density and HDL cholesterol alongside rises in triglycerides and LDL ¹². For ipamorelin, the absence of reported problems reflects the absence of long-term studies, not evidence of safety.

Status and compounding

Neither is approved anywhere ¹. According to our entries, FDA's advisory committee voted 13 to 1 in October 2024 against adding MK-677 to the list of substances pharmacies may compound, it sits in FDA's Category 2 for both kinds of compounding pharmacy, and FDA has said it is excluded from the definition of a dietary supplement; the same molecule is in paediatric trials as LUM-201 for growth hormone deficiency ¹. Ipamorelin acetate was placed in 503B Category 2 in 2023 and its 503A nomination was withdrawn ¹. Both are prohibited at all times under WADA's 2026 List ¹, and MK-677 can be detected in hair for weeks after use ¹³.

How the differences add up (as of October 3, 2026)

MK-677 is the better-studied compound, and its studies are the reason for caution: big hormonal effects, no clear functional benefit in older or ill people, and recurring metabolic and cardiac concerns. Ipamorelin is less studied, so less is known in either direction. Choosing a pill over an injection does not change the underlying question, which is whether raising growth hormone in healthy people does more good than harm, and no trial has shown that it does. Doses in the studies cited are not recommendations.

Frequently asked questions

Is MK-677 a peptide?

No. MK-677 (ibutamoren) is an oral small molecule that activates the ghrelin receptor, the same receptor ipamorelin acts on.

Which raises growth hormone more, MK-677 or ipamorelin?

No human study has compared them. MK-677 raised 24-hour growth hormone by about 97% and IGF-1 into the young-adult range in older adults; ipamorelin's human data are a single-dose pharmacokinetic study.

Is MK-677 safe?

It is not approved. Its trials showed rises in blood sugar and impaired glucose tolerance, and a hip-fracture trial was stopped early over a heart-failure signal.

Related on Grey Peptides

• MK-677
• Ipamorelin
• Hexarelin vs Ipamorelin

Sources

1. Grey Peptides dataset records for both compounds (status, half-life and studied doses as sourced on each entry); read October 2, 2026.
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. 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
4. 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
5. 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
6. 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
7. 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
8. Gobburu, J. V., et al. (1999). Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res, 16(9), 1412-6. PMID: 10496658
9. Beck, D. E., et al. (2014). Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. Int J Colorectal Dis, 29(12), 1527-34. PMID: 25331030
10. Raun, K., et al. (1998). Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol, 139(5), 552-61. PMID: 9849822
11. Cobani, E., et al. (2025). Hepatotoxicity induced by MK-677. BMJ Case Rep, 18(7). PMID: 40675653
12. 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
13. Kintz, P., et al. (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

Educational information, not medical advice. Each dose in this guide names its source, an approved label or a published study. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose.