Hexarelin dosage protocol

What Hexarelin Is

Hexarelin is a synthetic hexapeptide, a type of growth hormone-releasing peptide (GHRP). It is a synthetic analog of ghrelin and acts as a specific ligand for the growth hormone secretagogue (GHS) receptor (PMID 25645463, PMID 25278975). Unlike ghrelin, hexarelin is described as chemically more stable and functionally more potent (PMID 25278975).

GHRPs are synthetic, non-natural peptides that potently stimulate growth hormone (GH) secretion in animals and humans (PMID 9186261). They have no structural homology with Growth Hormone-Releasing Hormone (GHRH) and act via specific receptors in the pituitary or hypothalamus (PMID 9186261). Hexarelin is one of several GHRPs, including GHRP-1, GHRP-2, and GHRP-6, that have been synthesized and studied (PMID 9186261).

How it is Thought to Work

Hexarelin primarily works by binding to and activating the growth hormone secretagogue receptor (GHSR) in the brain (PMID 25278975). Its GH-releasing activity is marked and dose-related, effective after intravenous, subcutaneous, intranasal, and oral administration in humans (PMID 9186261). The GH-releasing effect is reproducible but can undergo partial desensitization with continuous infusion, while intermittent administration increases IGF-1 levels in animals and humans (PMID 9186261).

Mechanisms underlying GHRP effects are still being investigated, but they may counteract somatostatinergic activity in the pituitary and hypothalamus, and/or act partially via a GHRH-mediated mechanism (PMID 9186261). Beyond GHSR, hexarelin has been shown to bind to the non-GHSR CD36, which has been identified as a specific cardiac receptor for hexarelin and mediates its cardioprotective effects (PMID 25278975). Hexarelin also regulates peroxisome proliferator-activated receptor gamma (PPAR-γ) in macrophages and adipocytes (PMID 25645463).

Laboratory and Animal Studies

Studies in animals show that prolonged administration of GHRPs, including hexarelin, increases insulin-like growth factor 1 (IGF-1) levels (PMID 9186261). Ghrelin and hexarelin have been shown to exert growth hormone-independent cardiovascular activity (PMID 25645463).

In cell models, hexarelin regulates PPAR-γ in macrophages and adipocytes, which is significant for adipogenesis, lipid metabolism, and insulin sensitization (PMID 25645463). Ghrelin has shown protective effects on beta cells against lipotoxicity in cell studies, and administration of ghrelin reduces glucose levels and increases insulin-producing beta cell number and insulin secretion in pancreatectomized rats and streptozotocin-treated newborn rats, suggesting a role in pancreatic regeneration (PMID 25645463).

Metabolism studies in rats involving oral and intravenous administration of hexarelin identified at least three metabolites (PMID 23101768). Hexarelin and its metabolites were also investigated in human urine after nasal administration (PMID 25869809).

Human Evidence So Far

Hexarelin has potent GH-releasing activity in humans (PMID 9801990). In healthy individuals, the GH-releasing activity of GHRPs does not depend on sex but shows age-related variations, increasing from birth to puberty, maintaining similar levels in adulthood, and decreasing after the sixth decade, though remaining higher than GHRH (PMID 9186261).

In human volunteers, hexarelin, when administered nasally, was found to metabolize intensively and be excreted as a set of parent compounds with metabolites, including Hexarelin (1-3) free acid (PMID 25869809). The detection window in urine depends on individual metabolism, drug preparation, and administration route (PMID 25869809).

A study in patients with Prader-Willi syndrome (PWS) showed a blunted GH response to intravenous hexarelin compared to obese children, suggesting potential differences in pituitary GH deficiency or hypothalamic regulation of GH secretion in PWS patients (PMID 9801990).

Open Questions and Limitations

The precise mechanisms by which GHRPs, including hexarelin, exert their effects are still unclear (PMID 9186261). The existence of a natural ligand for the GHRP receptor, despite the receptor being cloned, has not yet been found (PMID 9186261).

Research into hexarelin has opened perspectives in endocrine, metabolic, and cardiovascular areas, suggesting potential therapeutic applications for diabetes and related heart diseases (PMID 25645463). The cardiovascular actions of hexarelin, independent of GH release, are an area of ongoing discussion (PMID 25278975).

The use of GHRPs like hexarelin in sports is regulated due to their potential to enhance performance by increasing GH secretion, leading to efforts to detect them and their metabolites in doping control (PMID 26811125, PMID 23101768).

Key Terms Explained

**GHRPs (Growth Hormone-Releasing Peptides):** Synthetic peptides that stimulate the release of growth hormone.

**GHS Receptor (Growth Hormone Secretagogue Receptor):** A specific receptor that binds ghrelin and synthetic compounds like hexarelin, leading to growth hormone release.

**GHRH (Growth Hormone-Releasing Hormone):** A natural hormone that also stimulates growth hormone release.

**IGF-1 (Insulin-like Growth Factor 1):** A hormone similar in molecular structure to insulin, which plays a role in childhood growth and continues to have anabolic effects in adults.

**PPAR-γ (Peroxisome Proliferator-Activated Receptor gamma):** A protein that regulates gene expression involved in lipid metabolism, glucose homeostasis, and inflammation.