Ghrelin

Also known as: Hunger hormone, Growth hormone secretagogue peptide, GHS-R1a ligand

Growth Hormone SecretagoguesWeight Loss & Metabolic

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

Research Dosage Notes

The following reflects doses used in published research studies. This is not medical advice.

Research context only as exogenous ghrelin. GHS-R1a agonists (e.g., MK-677 25 mg/day) used for ghrelin pathway activation clinically.

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

Synergistic Compounds

The following compounds have been studied alongside Ghrelin for potential complementary or synergistic effects:

IpamorelinGHRP-6MK-677 (Ibutamoren)

Learn More

Beginner's GuideNew to peptides? Start hereStacking GuideSynergistic combinationsAdministration RoutesSubQ, IM, oral, nasal & moreReconstitution CalculatorCalculate exact dosingPeptides vs SARMsFull comparisonHow Peptides Are MadeSPPS, purification & QC

References & Further Reading

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More Peptides in This Category

CJC-1295IpamorelinGHRP-6GHRP-2SermorelinTesamorelin