MK-677 (Capsules)

MK-677, known as ibutamoren or ibutamoren mesylate, is a potent, long-acting, orally active nonsteroidal ghrelin receptor agonist developed by Merck Research Laboratories [1]. Unlike peptidic growth hormone secretagogues, MK-677 is a small-molecule compound that mimics ghrelin to stimulate growth hormone release [2]. The compound operates through multiple mechanisms: increasing GHRH production, reducing somatostatin inhibition, and directly activating ghrelin receptor signaling in the pituitary [1]. Oral bioavailability exceeds 60%, making it suitable for preclinical research examining growth hormone-insulin-like growth factor I axis dynamics, bone metabolism, immune function, and metabolic signaling [3]. MK-677 has been studied in multiple preclinical models and limited clinical-stage research, demonstrating pulsatile GH secretion patterns.

Chemical Structure and Identification

• Compound Name: MK-677 (Ibutamoren Mesylate)
• Per capsule: 12.5 mg per capsule
• Molecular Formula: C₂₈H₄₀N₄O₈S₂ (mesylate salt)
• Molecular Weight: 528.7 g/mol
• CAS Number: 159752-10-0

Research Applications

• Growth Hormone Secretion: Investigation of GH pulsatility, IGF-I axis dynamics, and neuroendocrine regulation [1][2]
• Somatic Growth Research: Preclinical evaluation of lean body mass, bone mineral density, and growth marker responses [3]
• Bone Turnover Studies: Examination of bone anabolism markers and skeletal remodeling mechanisms [4]
• Metabolic Signaling: Research into glucose homeostasis, insulin sensitivity, and metabolic flexibility with GH stimulation [2]
• Sleep Quality Research: Investigation of ghrelin-mediated effects on sleep architecture and sleep stages [5]

Reference Citations

1. PubMed (30450851) – Effect of the Orally Active Growth Hormone Secretagogue MK-677 on Somatic Growth in Rats | https://pubmed.ncbi.nlm.nih.gov/30450851/
2. ScienceDirect (2025) – Knowing the minimal detectable dose of ibutamoren for hair testing and doping control | https://www.sciencedirect.com/science/article/abs/pii/S0009898125004577
3. PMC (6240568) – MK-677 Growth Hormone Secretagogue Effects on Body Composition and Growth Parameters | https://pmc.ncbi.nlm.nih.gov/articles/PMC6240568/
4. Journal of Bone and Mineral Research (1999) – MK-677 Increases Markers of Bone Turnover in Healthy and Functionally Impaired Elderly | https://pubmed.ncbi.nlm.nih.gov/
5. Cochrane Library – Prolonged oral treatment with MK-677, a novel growth hormone secretagogue, improves sleep quality in humans | https://www.cochranelibrary.com/

Important Regulatory Notice

These products are for research use only and are not intended for human consumption, therapeutic use, or diagnostic purposes. All compounds described herein have not been approved by the FDA for human use. These products are strictly intended for in vitro laboratory research and analytical purposes when conducted by qualified research professionals in licensed facilities. Users are responsible for ensuring compliance with all applicable laws regarding purchase and use of these materials.