GHRP-6
Also known as: Growth Hormone Releasing Peptide 6, Growth Hormone Releasing Hexapeptide
GHRP-6 is a synthetic hexapeptide that stimulates growth hormone release through the ghrelin receptor. It was one of the first growth hormone releasing peptides developed.
GHRP-6 Overview & Molecular Profile
GHRP-6 (Growth Hormone Releasing Peptide-6) is a synthetic met-enkephalin analog that includes unnatural D-amino acids. Developed in the 1980s, it was one of the first peptides shown to stimulate growth hormone release through the ghrelin receptor pathway. GHRP-6 is notable for its strong effects on appetite stimulation and its ability to work synergistically with GHRH analogs.
Mechanism of Action: Hormonal Signaling & Receptor Binding
GHRP-6 acts as a ghrelin receptor (GHSR-1a) agonist, stimulating GH release from the pituitary gland. Unlike GHRH, it works through a different receptor and signaling pathway, allowing for synergistic effects when combined. GHRP-6 also stimulates hunger through its ghrelin-mimetic effects on appetite centers. It can stimulate the release of cortisol and prolactin at higher doses, though to a lesser extent than some other GHRPs.
Research-Observed Effects
Growth Hormone Release
Research demonstrates GHRP-6 produces robust, dose-dependent increases in growth hormone levels through direct activation of the growth hormone secretagogue receptor (GHSR-1a) located on pituitary somatotroph cells. Clinical studies show peak GH concentrations occurring 15-30 minutes after subcutaneous administration, with increases of 5-15 fold above baseline depending on dosage and individual response variability. GHRP-6 stimulates GH release through mechanisms independent of growth hormone releasing hormone (GHRH), allowing for synergistic effects when these compounds are combined in research protocols for growth hormone deficiency treatment studies. The peptide works by amplifying the natural pulsatile pattern of GH secretion rather than creating sustained unphysiological elevations, which is considered advantageous for maintaining normal feedback regulation. Research has documented GHRP-6's effectiveness in various populations including elderly subjects where natural GH production is diminished, making it valuable for age-related growth hormone decline research and sarcopenia prevention studies.
Appetite Stimulation
GHRP-6 produces the most pronounced appetite stimulation among growth hormone releasing peptides due to its strong ghrelin-mimetic activity at hypothalamic appetite control centers, with research subjects reporting significant hunger increases within 20-30 minutes of administration. Studies demonstrate that GHRP-6 activates the same GHSR-1a receptors that natural ghrelin uses to signal hunger, triggering orexigenic (appetite-stimulating) neuropeptide release including NPY (neuropeptide Y) and AgRP (agouti-related peptide) in the arcuate nucleus. This robust appetite stimulation research application makes GHRP-6 particularly valuable for studying feeding behavior mechanisms, cachexia treatment approaches, and metabolic disorders characterized by appetite dysregulation. Research in anorexia and cancer-related cachexia models shows GHRP-6 can significantly increase food intake and body weight gain, with some studies documenting 20-40% increases in caloric consumption. The appetite effects, while sometimes considered a side effect in general GH research, provide unique opportunities for investigating the gut-brain axis, satiety signaling pathways, and hunger hormone physiology.
Gastric Motility
Studies demonstrate GHRP-6's significant effects on gastrointestinal function through ghrelin pathway activation, including accelerated gastric emptying, enhanced intestinal peristalsis, and increased gastric acid secretion. Research in gastroparesis models shows GHRP-6 administration can improve gastric emptying time by 30-50%, suggesting potential diabetic gastroparesis treatment applications and post-operative ileus prevention studies. The peptide stimulates the migrating motor complex (MMC), the coordinated intestinal contractions that occur between meals to sweep debris through the digestive tract, with implications for small intestinal bacterial overgrowth (SIBO) research. GHRP-6's prokinetic effects appear mediated through both direct smooth muscle stimulation and indirect effects via the enteric nervous system and vagal pathways. These gastrointestinal effects have positioned GHRP-6 as a valuable research tool for studying gut motility disorders, functional dyspepsia mechanisms, and the relationship between growth hormone signaling and digestive function.
Cardioprotective Research
Emerging research suggests GHRP-6 may possess cardioprotective properties through mechanisms potentially independent of growth hormone release, including direct effects on cardiac myocytes and vascular endothelial cells. Studies in ischemia-reperfusion injury models demonstrate reduced infarct size, improved left ventricular function, and decreased cardiomyocyte apoptosis following GHRP-6 treatment, with some studies showing up to 40% reduction in infarct area. Research indicates the peptide may activate cardioprotective signaling cascades including the PI3K/Akt pathway and reduce oxidative stress markers in cardiac tissue. GHRP-6 has been studied for effects on cardiac fibrosis, with some research suggesting reduced collagen deposition and improved ventricular compliance in heart failure models. These cardiovascular research applications have generated interest in GHRP-6 for coronary artery disease studies, post-myocardial infarction recovery research, and investigations into peptide-based cardioprotection strategies.
Research Dosing Information
Research studies have used dosages ranging from 25 mcg to 300 mcg, typically administered 2-3 times daily. The peptide is commonly studied in combination with GHRH analogs for synergistic effects.
Note: Dosing information is provided for research reference only and is based on published studies using research subjects. This is not a recommendation for any use.
Research Studies & References
Growth hormone releasing peptides
Bowers CY (1998). Journal of Clinical Endocrinology & Metabolism
This landmark review by Dr. Cyril Bowers, the pioneer who discovered growth hormone releasing peptides in the 1970s, provides comprehensive analysis of GHRP-6 and related compounds' mechanisms, pharmacology, and clinical potential. The paper details the discovery process that led to identification of the ghrelin receptor pathway and explains how GHRP-6 stimulates GH release through mechanisms distinct from and synergistic with growth hormone releasing hormone. Dr. Bowers presents extensive pharmacokinetic data showing dose-response relationships, peak GH levels occurring 15-30 minutes post-administration, and the duration of GH elevation in various study populations. The review examines GHRP-6's effects on other pituitary hormones including modest increases in ACTH, cortisol, and prolactin at higher doses, contrasting this with more selective newer peptides. This foundational work established GHRP-6 as a critical research tool for understanding growth hormone physiology and laid groundwork for clinical applications in growth hormone deficiency treatment and anti-aging research.
GHRP-6 effects on food intake and gastrointestinal motility
Asakawa A, Inui A, et al. (2003). Regulatory Peptides
This study investigated GHRP-6's orexigenic (appetite-stimulating) effects and gastrointestinal motility changes in rodent models, providing mechanistic insight into its ghrelin-mimetic properties. Researchers demonstrated that peripheral and central administration of GHRP-6 significantly increased food intake in a dose-dependent manner, with peak effects occurring 30-60 minutes after injection. The study documented that GHRP-6's appetite-stimulating effects were abolished in ghrelin receptor knockout mice, confirming the GHSR-1a receptor as the primary mediator. Gastric emptying studies revealed accelerated solid meal transit times of approximately 35% compared to controls, suggesting therapeutic potential for gastroparesis research. Additionally, the research identified increased expression of orexigenic neuropeptides NPY and AgRP in the hypothalamus following GHRP-6 treatment, establishing the neuroendocrine pathway underlying appetite stimulation and providing foundation for cachexia treatment studies.
Cardioprotective effects of GHRP-6 in experimental myocardial infarction
Berlanga J, Cibrian D, et al. (2007). Life Sciences
This preclinical study examined GHRP-6's cardioprotective properties in a rat model of ischemia-reperfusion injury, demonstrating significant heart-protective effects potentially independent of growth hormone release. Researchers subjected rats to 30-minute coronary artery occlusion followed by reperfusion and treated experimental groups with GHRP-6 at the time of reperfusion. Results showed approximately 40% reduction in infarct size, significantly improved left ventricular developed pressure, and reduced cardiac enzyme release (creatine kinase and troponin) in treated animals. The study identified activation of pro-survival kinases including Akt and reduced levels of pro-apoptotic markers in cardiac tissue. Importantly, the cardioprotective effects were observed at doses that did not significantly elevate circulating GH levels, suggesting direct cardiac mechanisms. These findings positioned GHRP-6 as a candidate for adjunctive treatment studies for acute myocardial infarction and stimulated investigation into peptide-based cardioprotection strategies.
Comparative Research
Explore in-depth research analyses and comparative studies featuring GHRP-6.
Frequently Asked Questions
Ipamorelin
C38H49N9O5
Ipamorelin is a selective growth hormone secretagogue and ghrelin receptor agonist. It stimulates the release of growth hormone from the pituitary gland without significantly affecting cortisol or prolactin levels.
CJC-1295
C152H252N44O42
CJC-1295 is a synthetic analog of growth hormone releasing hormone (GHRH) with a Drug Affinity Complex that extends its half-life significantly compared to native GHRH.