An orally active ghrelin mimetic that increases GH and IGF-1 — the only oral growth hormone secretagogue.
MK-677 (ibutamoren) is a non-peptide, orally active ghrelin receptor agonist. Unlike injectable peptide GHRPs, MK-677 can be taken as a pill. It mimics ghrelin's action on the GHS-R1a receptor in the pituitary and hypothalamus, stimulating the release of growth hormone. It also increases IGF-1 levels dose-dependently.
MK-677 is technically not a peptide — it's a spiroindane compound (small molecule). However, it is commonly discussed in peptide protocols because it targets the same ghrelin receptor as peptide GHRPs. Its oral bioavailability and long half-life (approximately 24 hours) allow once-daily oral dosing, making it popular in anti-aging and body composition contexts.
Despite extensive research and clinical trials (Merck and Lumos Networks), MK-677 has not received FDA approval for any indication. It is classified as a research chemical. It is not a selective androgen receptor modulator (SARM) despite sometimes being marketed alongside SARMs — an important distinction.
Clinical studies demonstrate sustained increases in GH and IGF-1 levels lasting the duration of use. A 2-year study in elderly patients showed increased lean body mass and improved bone mineral density. Sleep quality improvements (increased REM sleep) have been documented. Studies in children with GH deficiency showed growth acceleration.
MK-677 significantly increases appetite — a notable side effect that may be desirable or undesirable depending on the patient's goals. It also may impair insulin sensitivity and raise fasting glucose. These metabolic effects require monitoring, especially in patients with diabetes or metabolic syndrome.
📚 Key Reference: PMID: 9467542 (MK-677 elderly study), PMID: 9448585 (GH/IGF-1 effects)
Significant appetite increase is common and can be problematic. Water retention and edema are frequently reported. May impair insulin sensitivity and raise blood glucose — concerning for diabetics or those with metabolic syndrome. Increased cortisol and prolactin (mild). Muscle pain has been reported. Long-term safety for cancer risk (elevated GH/IGF-1) is not established. Not for use in active malignancy. Consult your provider about metabolic monitoring.
NOT FDA-approved. Not a licensed pharmaceutical in the US. Technically classified as a research chemical. Not legally prescribable as a conventional drug. Available online as a 'research chemical' — quality and purity are unverified. Patients seeking this should work with a licensed provider using regulated compounding pharmacies, not online gray-market sources.