Ghrelin
The stomach hormone that releases growth hormone and makes people eat more, studied by infusion and copied by drugs
Ghrelin is a 28-amino-acid hormone made in the stomach and identified in 1999 as the natural ligand of the growth hormone secretagogue receptor. It needs an octanoyl group on its third amino acid to work. Infused into healthy people it raised food intake by 28%; it is not a medicine itself, but drugs that copy it are.
What is it?
Synthetic growth hormone secretagogues were made before anyone knew what natural signal their receptor answered. In 1999 researchers purified it from rat stomach: a 28-amino-acid peptide with an octanoyl fatty acid on its third amino acid, without which it does nothing. They named it ghrelin, from a root meaning grow. Human ghrelin differs from the rat form by two amino acids.
Its best-known effect is hunger. In a crossover study in nine healthy volunteers, an intravenous ghrelin infusion increased the energy every person ate from a free buffet, by 28% on average, and raised appetite scores without changing gastric emptying. It was the first circulating hormone shown to make people eat more.
Daily life moves it too. When 12 healthy young men slept less for two nights, ghrelin rose 28% and leptin fell 18%, with hunger up 24%, especially for calorie-dense foods.
Ghrelin itself is not a medicine. Its receptor was first identified as the target of synthetic growth hormone secretagogues, which are reliable tests for growth hormone deficiency but weaker than growth hormone itself as growth promoters. Drugs acting on it, such as anamorelin and the secretagogues ipamorelin and MK-677, have their own entries.
At a Glance
Every value in this table is printed from the Grey Peptides dataset, the same record the compound explorer and comparison tool read, so the three can never disagree.
Published Research
These are the studies that describe ghrelin, read from their PubMed abstracts: its discovery, three human studies and two reviews.
The discovery
Purified from rat stomach as the natural ligand of the growth hormone secretagogue receptor: a 28-amino-acid peptide with an octanoylated serine 3 that releases growth hormone in vivo and in vitro.
It makes people eat more
In nine healthy volunteers, intravenous ghrelin raised the energy eaten from a free-choice buffet by 28% against saline, in every individual, and increased appetite without changing gastric emptying.
Short sleep raises it
In 12 healthy young men, two nights of restricted sleep raised ghrelin 28%, lowered leptin 18% and increased hunger 24% and appetite 23% against extended sleep.
Protein beats it
19 people moved to a 30%-protein diet ate 441 kcal a day less and lost 4.9 kg over 12 weeks, despite compensatory changes in leptin and ghrelin: leptin fell and ghrelin rose.
Ghrelin and the synthetic secretagogues
Ghrelin's receptor was first found as the target of synthetic, orally active growth hormone secretagogues. These work as diagnostic tests for growth hormone deficiency but fall short of recombinant growth hormone as growth promoters.
Ghrelin
A review of ghrelin's roles beyond energy balance: learning and memory, gut motility and acid secretion, sleep and wake rhythm, reward seeking, taste and glucose metabolism.
Side Effects & Contraindications
Reported Side Effects
From infusion studies; it is not a treatment.
Contraindications & Cautions
Not a treatment.
Legal Status
Ghrelin is not a medicine anywhere.
Frequently Asked Questions
?What is ghrelin?
A 28-amino-acid stomach hormone that stimulates appetite and growth hormone release through the ghrelin receptor.
?Does it really cause hunger?
Infused into nine healthy people, it raised food intake by 28% in every one of them.
?Does sleep affect it?
In 12 young men, two short nights raised ghrelin 28% and hunger 24%.
?Can I take it?
No ghrelin product is approved. Drugs that act on its receptor, such as anamorelin, are separate entries.
References
- [pubmed] Kojima M, et al. "Ghrelin is a growth-hormone-releasing acylated peptide from stomach." Nature, 1999;402(6762):656-60. PMID: 10604470.
- [pubmed] Wren AM, et al. "Ghrelin enhances appetite and increases food intake in humans." J Clin Endocrinol Metab, 2001;86(12):5992. PMID: 11739476.
- [pubmed] Spiegel K, et al. "Brief communication: Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite." Ann Intern Med, 2004;141(11):846-50. PMID: 15583226.
- [pubmed] Weigle DS, et al. "A high-protein diet induces sustained reductions in appetite, ad libitum caloric intake, and body weight despite compensatory changes in diurnal plasma leptin and ghrelin concentrations." Am J Clin Nutr, 2005;82(1):41-8. PMID: 16002798.
- [pubmed] Arvat E, et al. "Ghrelin and synthetic GH secretagogues." Best Pract Res Clin Endocrinol Metab, 2002;16(3):505-17. PMID: 12464231.
- [pubmed] Müller TD, et al. "Ghrelin." Mol Metab, 2015;4(6):437-60. PMID: 26042199.
- [other] US FDA, Drugs@FDA (openFDA): no application for ghrelin. Read September 30, 2026.
Sources & Citations
Studies were read from PubMed; regulatory status comes from openFDA, read September 30, 2026.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Consult a licensed healthcare provider before making health decisions.