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.
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. Last reviewed: 2026-07-05.
Related peptides: Ipamorelin, CJC-1295, Sermorelin.
Compare: MK-677 vs Ipamorelin, MK-677 vs CJC-1295, MK-677 vs Sermorelin.
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.