Ibutamoren, chemically known as MK-677, is a non-peptide, potent, long-acting, orally active secretagogue that stimulates the release of growth hormone (GH). It functions by mimicking the action of the endogenous hormone ghrelin, binding to the ghrelin receptor (GHSR) in the brain. Clinically, it has been studied for its potential to increase fat-free mass, improve bone mineral density, and alter lipid profiles, primarily through the resultant increase in both GH and Insulin-like Growth Factor 1 (IGF-1) levels. It is not a SARM but is often discussed within that pharmacological context.
Origin
Ibutamoren was developed in the 1990s as part of pharmaceutical research efforts to find an orally bioavailable compound that could safely and effectively elevate growth hormone levels for the treatment of GH deficiency and catabolic states. The chemical designation MK-677 is a laboratory code used during its development phase. Its origin is rooted in the quest to harness the anabolic and restorative properties of the somatotropic axis.
Mechanism
The primary mechanism of action is the agonism of the ghrelin receptor (GHSR1a), located in the pituitary and hypothalamus. Activation of this receptor potently stimulates the pituitary gland to release growth hormone, which in turn stimulates the liver to produce IGF-1. Importantly, Ibutamoren achieves this without significantly altering circulating cortisol levels, a common side effect of some other GH-releasing agents. This sustained elevation of the GH-IGF-1 axis drives anabolism and influences metabolic pathways.
Growth hormone secretagogues can alter long-term heart rhythm by modifying the heart's structure and electrical signaling, with risks varying by peptide.
Growth Hormone Secretagogues require careful selection and monitoring in insulin-resistant individuals to balance metabolic risks with body composition benefits.
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