Ghrelin
Ghrelin is the endogenous 28-aa octanoylated peptide from the stomach that activates GHS-R1a to stimulate GH release and appetite. All synthetic GHSPs were developed to mimic or improve upon ghrelin's GHS-R1a agonism.
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Compound Profile
Ghrelin
Key Data
Research reference only
Research Focus
Preclinical data
⚠ Research & Educational Use Only. Ghrelin is a research chemical documented here for scientific education. All information references peer-reviewed literature and preclinical/clinical study data. Not for human consumption. Not medical advice. Consult a licensed researcher or healthcare professional before any laboratory use.
- Most potent endogenous GH secretagogue — activates GHS-R1a in the pituitary and hypothalamus to trigger GH pulses
- Drives appetite via activation of NPY/AgRP neurons in the hypothalamic arcuate nucleus
- Cardioprotective in ischemia-reperfusion models via GHS-R1a on cardiomyocytes (independent of GH axis)
- Ghrelin is not FDA-approved for human use. It is a research chemical for scientific study only.
Research At a Glance
- Most potent endogenous GH secretagogue — activates GHS-R1a in the pituitary and hypothalamus to trigger GH pulses
- Drives appetite via activation of NPY/AgRP neurons in the hypothalamic arcuate nucleus
- Cardioprotective in ischemia-reperfusion models via GHS-R1a on cardiomyocytes (independent of GH axis)
- Promotes gastric motility and emptying — relevant to gastroparesis research
In Plain English
Simple summaryGhrelin is a 28-amino acid peptide primarily produced in the stomach -- your gut releases it when it's empty, and levels drop sharply after eating. It's the body's main hunger signal, but calling it just a 'hunger hormone' understates what it does. Ghrelin also directly stimulates growth hormone release from the pituitary (it's the endogenous ligand for the GHS-R1a receptor that synthetic GHRPs like GHRP-2 and ipamorelin are designed to target), and it has documented effects on sleep architecture, stress response, memory, and even cardiovascular protection. The acylated form (acyl-ghrelin) is the active form that drives GH release; des-acyl ghrelin is the more abundant circulating form and has different, sometimes opposing, metabolic effects.
- Most potent endogenous GH secretagogue — activates GHS-R1a in the pituitary and hypothalamus to trigger GH pulses
- Drives appetite via activation of NPY/AgRP neurons in the hypothalamic arcuate nucleus
- Cardioprotective in ischemia-reperfusion models via GHS-R1a on cardiomyocytes
The full scientific detail, mechanisms, citations, and dosing data, follows below.
What is Ghrelin?
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Ghrelin is a 28-amino acid peptide hormone predominantly secreted by endocrine X/A-like cells (P/D1 cells) of the gastric fundus. Its defining feature is an octanoyl (n-octanoic acid) modification on Ser3, which is essential for its binding to and activation of the growth hormone secretagogue receptor type 1a (GHS-R1a).
Ghrelin was discovered in 1999 by Kojima et al. as the endogenous ligand for GHS-R1a — a receptor that had been identified years earlier as the target for synthetic growth hormone secretagogues like GHRP-2 and GHRP-6. This discovery elegantly explained the mechanism by which all earlier GHSPs worked, and identified the stomach as a major endocrine organ in the GH axis.
**Two key functions:**
1. **GH Secretagogue**: Ghrelin acts synergistically with GHRH in the hypothalamus to amplify GH pulses from the anterior pituitary. Fasting-induced ghrelin rises coordinate with GHRH to produce larger nocturnal GH pulses and enhance the GH response to exercise.
2. **Orexigenic hormone**: Ghrelin is the only known circulating orexigen (appetite stimulant). Its levels rise before meals and fall after eating. It activates NPY/AgRP neurons in the hypothalamic arcuate nucleus to drive food-seeking behavior. Its antagonist LEAP-2 (also documented in this database) is the counter-regulatory signal.
The entire family of synthetic GHSPs — GHRP-2, GHRP-6, ipamorelin, hexarelin, and MK-677 — were designed to mimic or improve upon ghrelin's properties. They share GHS-R1a agonism but differ in selectivity (cardiac receptors, appetite effects), half-life, and potency.
Research applications include: GH deficiency research, cardiac ischemia protection, cancer cachexia, sarcopenia, GI motility disorders (gastroparesis), and metabolic disease (ghrelin/LEAP-2 ratio as a metabolic biomarker).
By the Numbers
Key Research Benefits
Documented effects observed in preclinical and clinical studies on Ghrelin. See all Growth Hormone Secretagogues peptides for comparison.
Side Effects & Risks
Adverse effects reported in the research literature. All data sourced from preclinical and clinical study reports. View all peptides' side effects →
Dosing Data from the Literature
Doses referenced below are sourced from published preclinical and clinical studies. Use the peptide dose calculator to convert these values to injection volume.
Ghrelin is primarily used as an endogenous reference standard in research. For experimental GH secretion studies, IV doses of 0.33-3.3 nmol/kg (approximately 1-10 mcg/kg) have been studied in healthy adults.
IV research dose: 1-10 mcg/kg as a bolus Half-life limitation: Enzymatic degradation of the octanoyl group limits duration of effect Research applications: GH secretion studies, appetite research, GI motility studies, cardiac research Synthetic analogues (GHRP-2, ipamorelin, hexarelin) are preferred for most research due to improved stability
Administration in Research Settings
Standard reconstitution and administration methodology for laboratory research use.
Ghrelin must be administered intravenously or subcutaneously due to extremely rapid degradation. The octanoyl modification at Ser3 is required for GHS-R1a binding and is cleaved by plasma butyrylcholinesterase and other esterases within minutes.
What the research doesn't show
Ghrelin's complexity is often underappreciated. It's not simply 'more ghrelin = more hunger and GH.' The acylated vs des-acylated balance, circadian rhythm, receptor desensitization, and interaction with other appetite hormones all shape what any given ghrelin signal actually does. Using exogenous ghrelin therapeutically is complicated by exactly this complexity.
Medical Expert Videos
Physicians, researchers, and pharmacologists explain Ghrelin, covering mechanisms of action, clinical context, and study findings.
Videos sourced from YouTube search. KnowYourPeptide does not endorse any individual creator. For research education only.
The Bottom Line
Ghrelin has a growing body of preclinical evidence and a well-characterised safety profile in research settings. The most-studied application is: most potent endogenous gh secretagogue — activates ghs-r1a in the pituitary and hypothalamus to trigger gh pulses.
The most commonly reported side effect in research subjects is potent appetite stimulation — significant hunger spike following ghs-r1a activation. It is a research chemical, not approved for human use.
Frequently Asked Questions
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Quick Reference
How It Compares
All the synthetic GHRPs (GHRP-2, GHRP-6, ipamorelin, hexarelin) are essentially engineered to activate the ghrelin receptor more selectively or durably than ghrelin itself. Leptin is the opposing appetite hormone -- ghrelin rises when energy stores are low, leptin rises when they're high. Understanding ghrelin's biology is foundational for understanding how every GHRP in this directory actually works.
Compare Ghrelin side-by-sideResearch Use Only
This information is for educational research purposes only. This is not medical advice. Consult a qualified healthcare professional.