MK-677 (Ibutamoren): Oral GH Secretagogue

What is MK-677 (ibutamoren)?

MK-677, known as ibutamoren, is an orally active compound that mimics ghrelin to signal the pituitary gland to release more growth hormone.

In the main human trial, once-daily oral MK-677 raised both GH and IGF-1 in healthy older adults over 12 months (Nass et al., 2008). Because it acts like ghrelin at the growth hormone secretagogue receptor, it is grouped with GH secretagogues rather than with GH itself. It does not add outside GH; it prompts the body to release more of its own.

How does MK-677 work in the body?

It binds the growth hormone secretagogue receptor, the same target ghrelin uses, prompting the pituitary to release GH in a pattern that tracks the body's own pulses.

This pulse-preserving action is part of why researchers studied once-daily oral dosing. Over a year, that dosing sustained raised GH and IGF-1 (Nass et al., 2008). GH then drives production of IGF-1, mostly in the liver, and IGF-1 carries out many of GH's downstream effects on tissue.

Is MK-677 a peptide, and why is it a pill instead of an injection?

Ibutamoren is a small molecule rather than a peptide, so it survives stomach acid and is absorbed as an oral dose, which is why it does not need to be injected.

Many peptide GH secretagogues, such as ipamorelin, are injected because digestion would break them apart. MK-677 is often listed next to those peptides because it hits the same receptor, but its chemistry is different. The 12-month trial used a once-daily oral route (Nass et al., 2008). For background on the wider category, see what are peptides.

What dosing has research reported for MK-677?

The main human trial used 25 mg by mouth once daily for 12 months in healthy older adults (Nass et al., 2008); this is what the study reported, not a recommendation.

The ranges below reflect what published studies and commonly studied research protocols report. This is educational, not a prescription or a personal recommendation.

The 25 mg per day figure has the strongest human documentation in the sources cited here. Lower amounts appear in discussion elsewhere, but they are not supported by the trial cited on this page. A personal dose belongs with a qualified clinician.

What is the half-life of MK-677?

A specific plasma half-life is not established in the sources cited here; what the trial confirms is that once-daily oral dosing sustained raised GH and IGF-1 across 12 months (Nass et al., 2008).

Once-daily dosing that holds IGF-1 up across a full day points to a duration of action long enough for a single daily dose. This page will not state an hour figure it cannot cite.

What did research find MK-677 does to body composition?

Over 12 months, MK-677 increased fat-free mass by about 1.1 kg in healthy older adults (Nass et al., 2008).

Fat-free mass measures lean tissue, which includes body water, so part of a measured gain can reflect fluid rather than contractile muscle. The trial's headline body-composition result was that roughly 1.1 kg lean-mass rise over a year (Nass et al., 2008). For how GH-axis compounds are studied for muscle more broadly, see peptides for muscle growth.

What are the reported side effects of MK-677?

The best-documented signal is metabolic: fasting blood glucose rose and insulin sensitivity fell at 25 mg per day over 12 months (Nass et al., 2008).

Because MK-677 raises GH and IGF-1, and GH can push blood sugar upward, the glucose finding fits its mechanism. Human safety data stay limited overall, and this page reports only what the cited trial documented. Anyone weighing these signals should work with a qualified clinician, especially with any history of blood-sugar problems.

How does MK-677 compare to ipamorelin and CJC-1295?

MK-677 is an oral small-molecule ghrelin mimetic, ipamorelin is an injectable selective GH secretagogue (Raun et al., 1998), and CJC-1295 is an injectable GHRH analog that sustained GH and IGF-1 (Teichman et al., 2006).

The practical split is route and target. MK-677 works orally at the ghrelin receptor. Ipamorelin also hits the ghrelin/GH secretagogue receptor but is a peptide given by injection, and it was characterized as highly selective for GH release (Raun et al., 1998). CJC-1295 uses a different door, the GHRH receptor, and was shown to sustain GH and IGF-1 (Teichman et al., 2006). Compare the injectable option on the ipamorelin page.

Is MK-677 sold as a medicine or supplement?

No. PeptaraLabs supplies MK-677 for laboratory and research use only; it is not a dietary supplement or an approved medicine.

Nothing here is medical advice, and nothing here promises a result. The research described comes from published trials in defined populations and may not apply to any individual.