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Growth hormone axis
MK-677: The One With a Two-Year Human Trial, and What It Found
The short answer
MK-677, also called ibutamoren, is an orally active growth hormone secretagogue. Unlike most compounds in this library it has been through a two-year randomised trial in older adults, which found it raised growth hormone and added lean mass, and also raised blood sugar.
Questions people ask about MK-677
MK-677 at a glance
| Also called | Ibutamoren; MK-0677; ibutamoren mesylate |
|---|---|
| What it is | A non-peptide growth hormone secretagogue, active by mouth |
| Acts on | GHS-R1a, the ghrelin receptor, like ipamorelin but orally and for far longer |
| Main system | Growth hormone axis: body composition, appetite, sleep |
| Evidence level | Unusually good for this library: a two-year randomised controlled trial plus two hip-fracture trials |
| FDA status (Oct 2026) | Not approved. It was developed as a drug, tested, and never submitted for approval |
| In sport | Prohibited at all times (WADA S2, growth hormone secretagogues) |
What is MK-677?
MK-677 is the odd one out in this library in two ways. It is not a peptide, it is a small molecule built to behave like one, and it works by mouth, which almost nothing else in the growth hormone class does.
It binds the same receptor as ghrelin and as ipamorelin, GHS-R1a, and asks the pituitary for growth hormone. The difference is duration: a single oral dose raises growth hormone and IGF-1 for roughly a day, rather than producing a pulse that fades in half an hour.
It was developed by a pharmaceutical company as a drug candidate, taken through real clinical trials, and then never submitted for approval. That history is why the evidence here is better than for most compounds on this site.
Targeted Peptide Systems profiles it at pp. 157–158, The Longevity Map at p. 85, and Regenerative Resilience covers it among the anabolic compounds at pp. 147–150.
How does MK-677 work?
Growth hormone comes in pulses, mostly in deep sleep, with GHRH opening the tap and somatostatin closing it. Ghrelin is a third signal, acting through its own receptor.
MK-677 occupies that ghrelin receptor and holds it. The consequences follow from how long it stays there:
- Growth hormone and IGF-1 stay elevated across the day rather than rising and falling with a pulse.
- Appetite rises, often markedly. That is the ghrelin receptor doing exactly what it does, and it is the effect people most often underestimate.
- The duration also means the feedback loops that normally limit the axis are under steady pressure, which is the practical difference between this and a short-acting secretagogue.
Metabolic Precision (pp. 69–73) sets out what a working growth hormone axis does, and p. 73 adds the caveat that matters here: the axis responds poorly in an insulin-resistant state, which is the same system MK-677 pushes on.
What does the research show?
The two-year trial. Nass and colleagues, 2008, in the Annals of Internal Medicine: healthy older adults took oral MK-677 or placebo for two years (reference 1). Growth hormone and IGF-1 rose to the levels of healthy young adults and stayed there. Fat-free mass increased. Those are real findings from a real trial, and very little else in this library has anything comparable.
What the same trial also found. Fasting blood glucose rose and insulin sensitivity fell. The strength and function measures did not improve alongside the body composition changes. Both halves come from the same paper, and reading only the first half is how this compound gets oversold.
The fracture trials. MK-677 was tested twice in older patients recovering from hip fracture (references 2, 3). Those trials are the reason the compound has a safety record at all, and they did not produce the functional recovery benefit the programme was looking for.
Where the evidence stands. The mechanism is settled and the body composition effect is measured, not inferred. What has not been shown is that the added lean mass translates into strength, function or anything else people take it for, and the metabolic cost is documented in the same data.
Side effects and cautions
Blood sugar is the headline, and it comes from the trial rather than from theory. Growth hormone reduces insulin sensitivity, and because MK-677 raises it continuously rather than in pulses, that effect was measurable over two years. Anyone with prediabetes, diabetes or a family history should treat glucose and HbA1c as the markers to follow, with a clinician reading them.
Appetite. Hunger increases, sometimes a lot. For someone trying to gain weight that is useful. For someone trying to lose it, the compound is working directly against the goal.
Water retention, puffiness in the hands and feet, joint aches, lethargy in the first weeks, and more vivid dreams are all commonly reported, and they are the familiar growth hormone picture.
Not for anyone with active cancer, uncontrolled diabetes or pituitary disease outside medical care. Metabolic Precision (p. 73) puts correcting metabolism before adding anything that leans on this axis.
Is MK-677 legal or FDA approved?
Not approved. MK-677 went through clinical development and was never submitted for approval, so there is no licensed product. It is widely sold as a research chemical, usually as a liquid or capsule.
It was not part of the July 2026 review. The FDA advisory committee that recommended six peptides that month did not take up MK-677, which is a different class of molecule anyway (references 4, 5).
Banned in sport. Growth hormone secretagogues are prohibited at all times under the World Anti-Doping Agency list, in and out of competition, and MK-677 is named (reference 6).
Because it is sold as a research chemical, what is in the bottle depends entirely on the supplier, which is what third-party testing exists to cover.
MK-677 vs ipamorelin, CJC-1295 and the GHRH analogs
They all end up at growth hormone. How they get there, and for how long, is the whole distinction.
- vs ipamorelin: same receptor, completely different duration. Ipamorelin produces a pulse that clears quickly and leaves the natural rhythm intact. MK-677 holds the receptor for about a day. Ipamorelin is injected; MK-677 is oral.
- vs CJC-1295 and sermorelin: those are GHRH analogs working through a different receptor. On mechanism they complement a ghrelin-receptor compound rather than compete with it, which is a statement about mechanism and not a protocol suggestion.
- vs tesamorelin: the only approved medicine in this group, for one specific population, with Phase 3 data behind it.
Metabolic Precision (pp. 240–241) gives the rule the book uses: one GHRH analog, optionally with one ghrelin-receptor compound. Stacking two that hit the same receptor gains nothing.
Risk, benefit, and the conversation this page is for
How to weigh it. Some research peptides have a quiet toxicology record, or an unfinished efficacy record. MK-677 is a different case: on its mechanism it genuinely moves physiology, in this case growth hormone and IGF-1, continuously rather than in pulses, and that is the reason to weigh it with due diligence rather than enthusiasm. Monitoring is paramount here, and the markers that matter are blood glucose and HbA1c above everything else, then fluid balance and appetite.
The regulatory picture is moving, selectively. In July 2026 an FDA advisory committee recommended six peptides, BPC-157, TB-500, KPV, MOTS-c, Epitalon and Semax, for the list of bulk substances compounding pharmacies may use. MK-677 was not among them, and it is a different class of molecule anyway: a small molecule built to act like a peptide, developed as a drug and never submitted for approval. Reading those decisions one at a time is more useful than treating every compound outside the approved list as equivalent.
Why the class is taken seriously. It carries something almost nothing else here does: a two-year randomised controlled trial. The body composition effect is measured rather than inferred. So is the rise in blood sugar, which comes from the same paper. The useful question is not whether engaging it does anything. It is whether you have done the due diligence to make an informed decision about engaging it at all: what your baseline looks like, what else you are taking, what you would measure along the way, and what would tell you to stop.
Which is the point of the series. Nothing here is a recommendation to use MK-677. People misuse approved medicines and unapproved compounds alike, and that is neither the purpose nor the intent of this page. The point is a better conversation than the internet usually allows: with a clinician who knows your history, your labs and everything else you take, and who can help build a plan that fits you.
MK-677: frequently asked questions
What is MK-677?
An orally active growth hormone secretagogue, also called ibutamoren. It acts on the ghrelin receptor and raises growth hormone and IGF-1 for about a day per dose.
Is MK-677 a SARM?
No, and the confusion is common because it is sold alongside them. SARMs act on the androgen receptor. MK-677 acts on the ghrelin receptor and does not touch androgens.
Does MK-677 build muscle?
In the two-year trial it increased fat-free mass in older adults (reference 1). The same trial did not find matching improvements in strength or function, which is the part usually left out.
Is MK-677 FDA approved?
No. It completed clinical trials and was never submitted for approval, so there is no licensed product.
What are MK-677’s side effects?
Raised blood glucose and reduced insulin sensitivity, measured over two years in the trial, plus increased appetite, water retention, joint aches, lethargy and vivid dreams.
Does MK-677 raise blood sugar?
Yes, and that is from trial data rather than theory. Fasting glucose rose and insulin sensitivity fell over two years of continuous use (reference 1). Glucose and HbA1c are the markers to follow.
MK-677 vs ipamorelin: which is better?
They work on the same receptor with very different durations. Ipamorelin gives a short pulse by injection; MK-677 holds the receptor for about a day and is taken by mouth. Better depends entirely on whether you want the natural pulse preserved.
Does MK-677 make you hungry?
Usually yes, often considerably. It is acting on the ghrelin receptor, and appetite is what that receptor does.
Is MK-677 banned in sport?
Yes. Growth hormone secretagogues are prohibited at all times under WADA’s S2 category, with MK-677 named.
Where MK-677 appears in our books
This page is the plain-language overview. The books go further: mechanism detail, evidence tiers, how MK-677 fits a full protocol, and the cautions that go with it. Page numbers refer to the print editions.
Targeted Peptide Systems
Profile, growth hormone secretagogues · pp. 157-158
About the bookLook Inside
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See how MK-677 fits a protocol
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Open the Protocol BuilderSee the book seriesReferences
- Nass R, Pezzoli SS, Oliveri MC, 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):601–611. View sourceThe two-year trial
- Adunsky A, Chandler J, Heyden N, 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):183–189. View source
- Bach MA, Rockwood K, Zetterberg C, et al. The effects of MK-0677, an oral growth hormone secretagogue, in patients with hip fracture. J Am Geriatr Soc. 2004;52(4):516–523. View source
- U.S. Food and Drug Administration. July 23–24, 2026: Meeting of the Pharmacy Compounding Advisory Committee. View source
- National Community Pharmacists Association. FDA advisory committee nominates six peptides for pharmacies to compound. July 31, 2026. View source
- World Anti-Doping Agency. The 2026 Prohibited List. View source
How this page is maintained. Regulatory status and trial results change. We review this page against current sources and update it as new information becomes available; the date at the top shows the last review.
Educational information only, not medical advice. MK-677 is discussed here for education. Nothing on this page is a recommendation to use it or a dosing guide. Talk to a qualified clinician before starting, stopping or combining any compound.