The only oral GH secretagogue — stimulates GH and IGF-1 through ghrelin receptor activation.
MK-677 (Ibutamoren, also known as L-163,191) is a non-peptide oral growth hormone secretagogue that mimics the action of ghrelin and activates the GHS-R1a (growth hormone secretagogue receptor 1a). It is the only orally bioavailable GH secretagogue, providing a convenient alternative to injectable GHRPs (growth hormone releasing peptides) such as GHRP-2 and GHRP-6. MK-677 was developed by Merck and has been evaluated in multiple Phase II human clinical trials for conditions including GH deficiency, muscle wasting, hip fracture recovery, and Alzheimer’s disease. It significantly elevates both pulsatile GH secretion and IGF-1 levels, with effects lasting approximately 24 hours from a single dose. Unlike injectable GH, MK-677 stimulates the body’s own GH production in a physiological pulsatile pattern, which is considered safer and more natural than exogenous GH administration. The compound has demonstrated improvements in body composition, bone mineral density, and sleep quality in human studies.
* Benefits based on preclinical/animal research unless otherwise noted.
MK-677 binds to and activates the ghrelin receptor (GHS-R1a) in the pituitary gland and hypothalamus, mimicking the action of the endogenous hunger hormone ghrelin. This activation stimulates the pituitary to release GH in pulsatile bursts, which in turn stimulates the liver to produce IGF-1 (insulin-like growth factor 1). Unlike synthetic GH, MK-677 preserves the natural pulsatile pattern of GH secretion, which is important for maintaining GH receptor sensitivity and avoiding the desensitization that can occur with continuous GH exposure. MK-677 has a half-life of approximately 24 hours, allowing for once-daily dosing. Bedtime administration aligns with the natural nocturnal GH pulse and may enhance sleep quality through GH’s effects on slow-wave sleep architecture. The compound also increases ghrelin signaling in the hypothalamus, which stimulates appetite — a common and expected effect that should be managed through dietary awareness.
Protocol Notes: Bedtime dosing aligns with natural GH pulse. Start with 10 mg to assess tolerance. Increased hunger is common — manage caloric intake. Monitor IGF-1 every 3 months.
Store at room temperature, away from light and moisture.
When sourcing MK-677 (Capsule) for research purposes, the following quality benchmarks should be verified before use.
Store at room temperature, away from light and moisture.
The statements made within this website have not been evaluated by the US Food and Drug Administration. The products and information provided are not intended to diagnose, treat, cure, or prevent any disease. This website is intended for educational and research purposes only. Many peptides described on this site are not approved by the FDA for human therapeutic use and are classified as research chemicals. Nothing on this site constitutes medical advice.
Moderate Evidence — Multiple animal studies and/or early human trials. Reasonable confidence in mechanism, but human data is limited.
Peptides commonly used alongside MK-677 (Capsule) for synergistic effects.
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