MK-677

Product Overview

MK-677 (Ibutamoren) is a synthetic, orally active growth hormone secretagogue that acts as a selective agonist of the ghrelin receptor (GHSR-1a). Unlike peptide-based growth hormone secretagogues, MK-677 is a non-peptide small molecule with high oral bioavailability, making it a widely used tool compound in research investigating the growth hormone/IGF-1 axis.

Research-Chem.uk supplies MK-677 as a laboratory research compound intended strictly for in-vitro, analytical and scientific research applications. It is not intended for human or veterinary use.

What Is MK-677 (Ibutamoren)?

MK-677, also known as Ibutamoren or Ibutamoren Mesylate, is a potent, long-acting, orally active agonist of the ghrelin receptor (GHS-R1a). It was originally developed as a tool compound to investigate the growth hormone secretagogue receptor and the downstream effects of sustained GH and IGF-1 elevation in research models.

Unlike peptide-based GH secretagogues such as GHRP-6 or Ipamorelin, MK-677 is a non-peptide small molecule. This confers high oral bioavailability and a prolonged half-life, making it particularly useful in research settings where sustained receptor activation is required.

MK-677 stimulates GH secretion by mimicking the action of ghrelin at the GHSR-1a receptor. This leads to pulsatile GH release from the pituitary and subsequent elevation of circulating IGF-1 in research models. The compound does not suppress endogenous GH secretion in the way that exogenous GH administration does, making it a useful tool for studying the GH/IGF-1 axis.

MK-677 is also known by the following identifiers:

• Ibutamoren
• Ibutamoren Mesylate
• L-163,191
• CAS: 159752-10-0

Mechanism of Action

MK-677 acts as a selective, non-peptide agonist of the growth hormone secretagogue receptor type 1a (GHSR-1a), the endogenous receptor for ghrelin. Activation of GHSR-1a in the hypothalamus and pituitary stimulates GH release through a mechanism distinct from GHRH-mediated GH secretion.

The primary signalling pathway involves:

• GHSR-1a receptor binding and activation
• Gq/11 protein coupling and phospholipase C activation
• IP3-mediated intracellular calcium mobilisation
• Pituitary somatotroph stimulation and GH secretion
• Hepatic IGF-1 production in response to elevated GH

MK-677 also acts at the hypothalamic level to stimulate GHRH release and inhibit somatostatin tone, further amplifying GH secretion. The compound's long half-life (approximately 24 hours in research models) allows for sustained receptor engagement, which is useful in experimental designs requiring prolonged GH/IGF-1 axis activation.

Because MK-677 acts through the ghrelin receptor rather than directly on the pituitary, it preserves the pulsatile nature of GH secretion, which is an important consideration in research models examining physiological GH dynamics.

MK-677 Research Applications

What Does the Research Say?

MK-677 has been the subject of a substantial body of pre-clinical and clinical research, primarily focused on its ability to stimulate GH and IGF-1 secretion and the downstream effects of sustained GH/IGF-1 axis activation.

Early research established MK-677 as a potent and selective GHSR-1a agonist with high oral bioavailability and a long duration of action. Studies in research models demonstrated consistent, dose-dependent increases in GH pulse amplitude and circulating IGF-1 concentrations following MK-677 administration.

Clinical research has examined MK-677 in the context of GH deficiency, age-related GH decline, body composition and bone metabolism. Studies have reported increases in IGF-1 and GH secretion, along with changes in lean body mass and bone turnover markers in research subjects. However, MK-677 is not an approved medicine and these findings should not be interpreted as evidence of clinical efficacy or safety for any therapeutic indication.

Research has also examined the metabolic effects of MK-677, including its influence on insulin sensitivity and glucose metabolism. GH has known effects on insulin signalling, and sustained GH elevation can affect glucose homeostasis. These metabolic interactions are an important consideration in research designs involving MK-677.

MK-677 remains a widely used tool compound in GH/IGF-1 axis research due to its oral activity, long half-life and well-characterised receptor pharmacology. It provides a useful experimental model for investigating the downstream effects of sustained GHSR-1a activation without the need for injectable peptide administration.

Research References

• Chapman IM, et al. (1996). Stimulation of the growth hormone (GH)-insulin-like growth factor I axis by daily oral administration of a GH secretogogue (MK-677) in healthy elderly subjects. Journal of Clinical Endocrinology & Metabolism, 81(12), 4249–4257.

  PMID: 8954023 · DOI: 10.1210/jcem.81.12.8954023

• Svensson J, et al. (1998). Two-month treatment of obese subjects with the oral growth hormone (GH) secretagogue MK-677 increases GH secretion, fat-free mass, and energy expenditure. Journal of Clinical Endocrinology & Metabolism, 83(2), 362–369.

  PMID: 9467543 · DOI: 10.1210/jcem.83.2.4539

• Nass R, et al. (2008). Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults. Annals of Internal Medicine, 149(9), 601–611.

  PMID: 18981485 · DOI: 10.7326/0003-4819-149-9-200811040-00003

• Copinschi G, et al. (1997). Prolonged oral treatment with MK-677, a novel growth hormone secretagogue, improves sleep quality in man. Neuroendocrinology, 66(4), 278–286.

  PMID: 9349662 · DOI: 10.1159/000127249

• Murphy MG, et al. (1998). Oral administration of the growth hormone secretagogue MK-677 increases markers of bone turnover in healthy and functionally impaired elderly adults. Journal of Bone and Mineral Research, 14(7), 1182–1188.

  PMID: 10404017 · DOI: 10.1359/jbmr.1999.14.7.1182

• Patchett AA, et al. (1995). Design and biological activities of L-163,191 (MK-0677): a potent, orally active growth hormone secretagogue. Proceedings of the National Academy of Sciences, 92(15), 7001–7005.

  PMID: 7624358 · DOI: 10.1073/pnas.92.15.7001

MK-677 Product Specifications

Quality and Purity

At Research-Chem.uk, analytical quality and batch traceability are central to our research compound range.

This MK-677 batch is supplied with a stated 99.9% purity, with HPLC analysis used to assess the supplied material. Each batch is supported by a Certificate of Analysis (COA) providing analytical documentation for the supplied material.

The product is supplied as a 30ml solution at 25mg/ml concentration. Researchers should always refer to the relevant batch-specific COA when recording analytical characteristics for experimental work.

Laboratory Research Applications

MK-677 may be suitable for laboratory investigations involving:

• GHSR-1a receptor pharmacology
• GH secretion dynamics
• IGF-1 regulation
• GH/IGF-1 axis biology
• Pituitary somatotroph function
• Hypothalamic neuroendocrine research
• Lean mass and nitrogen balance models
• Protein synthesis pathways
• Bone metabolism and turnover
• Osteoblast biology
• Glucose and insulin metabolism
• Lipid metabolism
• Sleep and GH secretion research
• Age-related GH decline models
• GH deficiency research models
• Comparative GH secretagogue studies
• Analytical and anti-doping research

MK-677 is supplied strictly as a research compound and is not intended to diagnose, treat, cure or prevent any disease or medical condition.