MK-677 (Ibutamoren) is a potent, long-acting, orally-active, non-peptide ghrelin receptor (GHS-R1a) agonist that stimulates growth hormone release without injections. Unlike injectable GH peptides such as GHRP-6 or Ipamorelin, MK-677 can be taken orally and maintains elevated GH and IGF-1 levels for up to 24 hours. It has been studied in several human clinical trials for GH deficiency, muscle wasting, bone density, and sleep quality, but is not FDA-approved for any indication.
3 vendors tracked by PeptideAtlas list MK-677, priced from $49.99 to $200. The lowest price per milligram is $4.00/mg at Peptide Labs (12.5mg). 1 independent Janoshik purity test cover MK-677 across 1 vendor.
Category: Growth Hormone Secretagogue. Evidence rating: C (early/mixed human evidence).
Clinical status: Multiple Phase II trials completed. Not FDA-approved. Investigational.
MK-677 binds to the ghrelin receptor (GHS-R1a) in the pituitary gland and hypothalamus, mimicking the hunger hormone ghrelin. This activates the GH secretagogue pathway, amplifying the natural pulsatile release of growth hormone and subsequently IGF-1, without suppressing the…
Research base: 2 registered clinical trials and 10 indexed publications reference MK-677.
Safety considerations: Common: increased appetite (ghrelin agonism), water retention/mild edema, transient muscle pain; Metabolic: may elevate fasting blood glucose and reduce insulin sensitivity (dose-dependent); important for diabetics and pre-diabetics; Fatigue and lethargy reported by some users.
Reviewed by the PeptideAtlas Editorial Team.
| Molecular formula | C27H36N4O5S |
|---|---|
| Molecular weight | ~528.7 g/mol (624.8 as mesylate salt) |
| CAS number | 159634-47-6 |
| Half-life | ~4–6 hours (plasma); functional activity ~24 hours |
| Bioavailability | Orally bioavailable |
| Production method | synthetic |
| Anti-doping status | Prohibited in sport (WADA) |
| US regulatory status | Not FDA-approved. Removed from FDA Category 2 on April 15, 2026. PCAC review scheduled July 23-24, 2026. Investigational compound. Available as a research chemical. Not a controlled substance. |
| Vendor | Size | Price | Price per mg |
|---|---|---|---|
| Peptide Labs | 12.5mg | $49.99 | $4.00/mg |
| SwissChems | 10mg | $89.95 | $9.00/mg |
| Peplogix Peptides | 20mg | $200 | $10.00/mg |
| Vendor | Best tested purity |
|---|
Related peptides: Ipamorelin, CJC-1295, Sermorelin.
Compare: MK-677 vs Ipamorelin, MK-677 vs CJC-1295.
No. MK-677 is neither a steroid nor a SARM. It is a non-peptide ghrelin receptor agonist (growth hormone secretagogue). It does not directly affect testosterone or androgen receptors.
Yes, oral administration is its primary route. Unlike injectable GH peptides, MK-677 is orally bioavailable with a long functional half-life of ~24 hours, allowing once-daily dosing.
No. MK-677 amplifies the body's natural GH pulsatile release through ghrelin receptor agonism. It does not suppress the hypothalamic-pituitary axis like exogenous HGH does.
Yes. Studies show MK-677 can elevate fasting blood glucose and reduce insulin sensitivity, particularly at higher doses and with long-term use. Blood glucose monitoring is recommended, especially for pre-diabetics.
Yes. MK-677 is prohibited at all times by WADA under the S2 category (Growth Hormone Secretagogues). It is detectable in anti-doping tests.
Vendors with independent lab tests for it: idenex.biz.
Vendors stocking it: SwissChems, PureRawz, Peplogix Peptides, Supopeptide, NCRP Canada, Disguised Alpha.