Ghrelin
Also known as: Hunger hormone, Growth hormone secretagogue peptide, GHS-R1a ligand
Overview
Ghrelin is a 28-amino acid acylated peptide hormone produced primarily by X/A-like cells of the gastric fundus. It is the endogenous ligand for the growth hormone secretagogue receptor (GHS-R1a), stimulating GH release, appetite, and gastric motility. As the only known circulating orexigenic (appetite-stimulating) hormone and the endogenous counterpart to synthetic GHS-R1a agonists like GHRP-2, GHRP-6, Ipamorelin, and MK-677, ghrelin occupies a central position in metabolic and GH physiology research. Its unique octanoyl group modification at Ser3 is essential for GHS-R1a binding.
Mechanism of Action
Acylated ghrelin (the active form, octanoylated at Ser3 by ghrelin O-acyltransferase/GOAT enzyme) binds GHS-R1a (GHSR) on pituitary somatotrophs, triggering Gq-mediated phospholipase C activation, IP3-mediated calcium release, and GH secretion. In the hypothalamus, ghrelin activates NPY/AgRP neurons while suppressing POMC neurons, powerfully stimulating appetite. In the gastrointestinal tract, ghrelin via GHS-R1a promotes gastric motility and acid secretion. Ghrelin levels rise markedly before meals (promoting hunger) and fall post-meal. Des-acyl ghrelin (without octanoyl group) has distinct biological activities via non-GHS-R1a receptors.
Potential Benefits
- Endogenous GH secretagogue (natural GH pulse driver)
- Understanding ghrelin enabled development of all GHS-R1a agonist drugs
- Research target for anti-obesity drugs (ghrelin antagonists)
- Gastroparesis treatment target (promotes gastric motility)
- GH deficiency and cachexia therapeutic target
Dosage Protocols
The following reflects doses used in published research studies. This is not medical advice. Consult a qualified healthcare professional.
| Beginner | Research/clinical only — not a consumer peptide |
| Intermediate | N/A |
| Advanced | N/A |
| Cycle Duration | Research protocols: hours to days |
Endogenous appetite hormone. Therapeutics target ghrelin pathway (GHRPs are synthetic mimetics).
Use our Reconstitution Calculator to determine exact syringe units for your protocol.
Routes of Administration
Intravenous (research) 100%
Primary research route.
Subcutaneous Moderate — rapidly degraded
Acylated ghrelin requires stable formulation.
Read our full Routes of Administration Guide for detailed comparison of all delivery methods.
Stacking Protocols
Popular research stacks involving Ghrelin:
Research Context Only
Endogenous ghrelin is not used in stacking — GHRP-2/GHRP-6/Ipamorelin/MK-677 are synthetic mimetics used instead.
Explore our complete Peptide Stacking Guide for more combinations and safety considerations.
Reconstitution
| Storage | Refrigerate at 2-8°C after reconstitution. Do not freeze reconstituted solution. |
|---|
Typical vial sizes: 0.5-1 mg (research). Add bac water slowly down the side of the vial, swirl gently — do not shake. Use insulin syringe for precise dosing.
Need exact syringe measurements?
Amino Acid Sequence
Gly-Ser-Ser(octanoyl)-Phe-Leu-Ser-Pro-Glu-His-Gln-Arg-Val-Gln-Gln-Arg-Lys-Glu-Ser-Lys-Lys-Pro-Pro-Ala-Lys-Leu-Gln-Pro-Arg
Side Effects & Safety
- Appetite stimulation (primary pharmacological effect)
- Hyperinsulinemia at pharmacological doses
- Gastric acid secretion increase
Safety & Contraindications
This information is for educational purposes only. Consult a qualified healthcare provider before using any peptide.
Pregnancy / Lactation
Bleeding Disorders
Active Skin Infection at Injection Site
Pharmacokinetics
| Half-Life | ~10-30 minutes (acylated ghrelin) |
|---|---|
| Storage | Store lyophilized peptide at -20°C (long-term) or 2-8°C (short-term, under 30 days). Reconstituted: refrigerate at 2-8°C and use within 28-30 days. Protect from light. Do not freeze reconstituted solution. |
Synergistic Compounds
The following compounds have been studied alongside Ghrelin for potential complementary or synergistic effects:
Learn More
References & Further Reading
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