What it is
MK-677 is an oral growth hormone secretagogue, a compound that prompts the body to release growth hormone (GH). Technically it is not a peptide: it is a non-peptide ghrelin mimetic, meaning a small molecule that imitates ghrelin, the hormone that signals through the ghrelin receptor. It is studied for increasing GH and insulin-like growth factor 1 (IGF-1) levels, and because it is taken by mouth it is supplied as capsules or liquid rather than as an injection.
In the PeptidesAI encyclopedia it is categorized under growth hormone. It is listed alongside peptides even though it is a different kind of molecule, which is why it has no reconstitution step.
How it's thought to work
MK-677 stimulates growth hormone release through the ghrelin receptor. It belongs to a group of compounds described as non-peptide mimetics of the growth hormone-releasing peptides, and its GH-releasing effect has been demonstrated in people after oral administration. The PeptidesAI encyclopedia also describes it as having a long half-life.
What the research says
In a two-year, double-blind, randomized, placebo-controlled trial of 65 healthy adults aged 60 to 81, oral MK-677 raised growth hormone and IGF-1 levels to those of healthy young adults. After one year, mean fat-free mass rose by 1.1 kg in the MK-677 group and fell by 0.5 kg in the placebo group, and body weight rose 2.7 kg versus 0.8 kg. The increase in fat-free mass did not translate into changes in strength or function, and the authors noted that the study was too small and too short to evaluate functional outcomes.
MK-677 is not FDA-approved.
Reported side effects
In the trial above, the most frequent side effects were an increase in appetite that subsided within a few months and transient, mild lower-extremity edema and muscle pain. Fasting blood glucose rose on average and insulin sensitivity decreased in the MK-677 group, and average cortisol levels rose slightly.
The PeptidesAI encyclopedia also lists significant appetite increase, water retention, numbness or tingling, increased blood sugar and lethargy among reported effects.
Form
MK-677 is taken by mouth as capsules or liquid, so it is not reconstituted.
Important notes
MK-677 is not FDA-approved for any use and is an investigational compound. Because it is taken by mouth, there is no reconstitution or injection step.
Sources
- Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial. Nass R et al. Ann Intern Med, 2008. Human trial
- Growth hormone-releasing peptides. Ghigo E et al. Eur J Endocrinol, 1997. Review
Frequently asked questions
These questions cover the same ground as the sections above, in a shorter format.
What is MK-677?
An oral, non-peptide ghrelin mimetic that is studied for increasing growth hormone and IGF-1 levels. It is taken by mouth and is not a peptide.
How is MK-677 thought to work?
It stimulates growth hormone release through the ghrelin receptor, which is why it is called a ghrelin mimetic.
What does the research on MK-677 say?
A two-year randomized, placebo-controlled trial in healthy older adults found higher growth hormone and IGF-1 levels and an increase in fat-free mass, without changes in strength or function. It is not FDA-approved.
What are the reported side effects of MK-677?
In that trial: increased appetite that subsided over a few months, transient mild edema and muscle pain, a small rise in fasting blood glucose and reduced insulin sensitivity.
The full entry, plus the calculator
The PeptidesAI app has the complete encyclopedia entry for MK-677 (Ibutamoren) — one of 70 compounds covered — plus the reconstitution calculator, a dose log and reminders. Free to download on iPhone.
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