What Is Ghrelin? The Gut Hormone Behind Hunger and GH
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Ghrelin

Also called hunger hormone, acyl ghrelin, GHS-R ligand · Reviewed

Definition: Ghrelin is a peptide hormone first purified from the stomach. It raises appetite and triggers growth hormone release by switching on the growth hormone secretagogue receptor. It was discovered in 1999 as the body's own signal for the receptor that synthetic GHRPs had already been shown to use.

How it was found

Kojima and colleagues purified ghrelin from rat stomach and reported it in Nature in 1999. It is a chain of 28 amino acids with a fatty acid (an octanoyl group) attached to the third amino acid, serine. That fatty acid is essential for its activity. Human ghrelin differs from rat ghrelin by only two amino acids.

The name comes from "ghre", a Proto-Indo-European root meaning "grow". The paper concluded that GH release may be controlled by ghrelin as well as by GHRH.

Appetite and other effects

StatPearls describes ghrelin as a hormone known for stimulating appetite and feeding, with roles in energy balance and carbohydrate metabolism. Its effects on eating run both through basic need and through brain areas linked to reward and motivation.

Drugs that act on the ghrelin receptor

Macrilen (macimorelin) is an FDA-approved growth hormone secretagogue receptor agonist, taken by mouth. Its label use is to diagnose adult growth hormone deficiency, not to treat anything.

Timing from the Macrilen label

  1. Highest GH levels: 30 to 90 minutes after the dose.
  2. Mean half-life of macimorelin: 4.1 hours. 5 half-lives = 5 × 4.1 = 20.5 hours.
  3. A liquid meal cut AUC by 49%. The label PK figures come from people who had fasted for at least 8 hours.

Read more on Dose Track: Ipamorelin guide

General education drawn from labels and published studies, not personal medical advice. Your prescriber, pharmacist and the label that came with your product are the final word.
GHRP (growth hormone-releasing peptide)A GHRP (growth hormone-releasing peptide) is a small synthetic peptide that makes the pituitary release… Growth hormone secretagogueA growth hormone secretagogue is a compound that makes your pituitary gland release more of its own growth… GHRH (growth hormone-releasing hormone)GHRH (growth hormone-releasing hormone, also called GRF) is a hormone made in the hypothalamus, part of… Receptor agonistA receptor agonist is a drug that binds to a receptor on a cell and switches it on, so the cell responds…

Frequently asked questions

Why is ghrelin called the hunger hormone?+
Because it stimulates appetite and feeding. It was first purified from the stomach in 1999.
Is there an approved drug that copies ghrelin?+
Macrilen (macimorelin) is an FDA-approved agonist of the same receptor. Its label use is a test to diagnose adult growth hormone deficiency.

Sources

  1. Kojima M et al. Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature 1999. PMID 10604470
  2. Young ER, Jialal I. Biochemistry, Ghrelin. StatPearls 2023. PMID 31613472
  3. Macrilen (macimorelin) US prescribing information, sections 1 and 12, DailyMed

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