Ghrelin

lenomorelin (INN), "hunger hormone", acyl-ghrelin (active form), des-acyl ghrelin (unacylated form), GHRL gene product

Sexual health, hormones & signalling

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Summary

Class: Naturally occurring 28-amino-acid peptide hormone, unusual in carrying an eight-carbon fatty acid (octanoyl) on its third amino acid, which is required for receptor activity
Mechanism: The body's own ligand for the growth hormone secretagogue receptor (GHS-R1a): triggers GH release from the pituitary, stimulates appetite via the hypothalamus, speeds stomach emptying and raises blood glucose by restraining insulin
Routes studied: Intravenous and subcutaneous infusion/injection in human trials; many routes in animals
Dose range reported: Human trials: IV boluses of ~1 µg/kg; infusions of 1–5 pmol/kg/min; subcutaneous 2–10 µg/kg once or twice daily in cachexia studies (e.g. 2 µg/kg twice daily for 3 weeks in COPD). Community use of ghrelin itself is rare; most community "ghrelin" use is actually of mimetics (GHRP-6, ipamorelin, MK-677)
Half-life: Acyl-ghrelin ~10–30 minutes in plasma; it is rapidly de-acylated to des-acyl ghrelin, which has a longer half-life but does not activate GHS-R1a
Storage: Lyophilised: freeze or refrigerate; the acyl group is unstable. Reconstituted: use promptly, refrigerate, protect from light
Regulatory status: Not approved as a medicine anywhere. Its synthetic mimetic anamorelin is approved in Japan for cancer cachexia; the diagnostic mimetic macimorelin is approved in the US and EU for testing GH deficiency

Doses are as reported in studies or by the community — never recommendations.

1What it is

Ghrelin is a hormone your stomach makes and releases into the blood, mostly when it is empty. It was discovered in 1999 by Masayasu Kojima and Kenji Kangawa in Japan, who went looking for the natural molecule that fits the "orphan" receptor through which synthetic GH (GHRP-6 and its relatives) were already known to work (Kojima 1999, Nature). Finding the body's own ligand after the drugs was unusual, and it is why every GH-releasing peptide on this site — ipamorelin (#4), GHRP-2, GHRP-6, hexarelin, MK-677, anamorelin — is best understood as a ghrelin mimic.

Ghrelin levels rise before meals and fall after, rise during weight loss and fall in obesity, and are very high in anorexia nervosa and cachexia. It is a naturally occurring molecule; synthetic human ghrelin is used in research but has not become a medicine, mainly because of its short and because long-acting mimetics are easier to use.

2How it's thought to work

Growth hormone. ghrelin acts on receptors in the pituitary and hypothalamus to release GH in pulses, synergising with GHRH. It is the most potent natural GH releaser known on a molar basis.

Appetite. it activates NPY/AgRP neurons in the arcuate nucleus of the hypothalamus — the same circuit leptin (#119) inhibits — producing hunger within minutes of infusion.

Gut. speeds gastric emptying and gut motility, which is why mimetics were trialled for post-operative ileus and gastroparesis.

Glucose. suppresses insulin secretion and raises blood glucose; blocking ghrelin improves glucose tolerance in animals.

Other. reported cardioprotective, anti-inflammatory, anxiolytic and sleep effects in animals; also raises ACTH/cortisol and prolactin modestly, unlike the "clean" synthetic ipamorelin.

Des-acyl ghrelin. , the major circulating form, does not bind GHS-R1a and appears to have separate, sometimes opposing metabolic effects through an unidentified receptor.

The stomach's own hunger hormone at the GHS-R1a receptor. The same signal drives a growth hormone pulse from the pituitary and an appetite signal in the hypothalamus.Schematic — not to scale

3What the research shows

Graded A (small)

GH release and appetite in healthy people

IV ghrelin produces a large, dose-dependent GH peak in healthy volunteers (Takaya 2000, J Clin Endocrinol Metab) and, in a placebo-controlled crossover, increased food intake at a buffet meal by about 28% (Wren 2001, J Clin Endocrinol Metab). [2][3]

Graded A (small) / B

Cancer anorexia/cachexia

A placebo-controlled crossover in cancer patients with appetite loss showed increased energy intake with IV ghrelin (Neary 2004, J Clin Endocrinol Metab). Longer studies are small. The field moved to the oral mimetic anamorelin, which in Phase 3 (ROMANA 1 and 2) increased lean body mass but not handgrip strength (Temel 2016, Lancet Oncol); approved in Japan in 2021, refused by the EMA in 2017. [4][7]

COPD and heart-failure cachexia

Open-label and small controlled studies of IV ghrelin twice daily for 3 weeks reported gains in weight, muscle strength and walking distance in underweight COPD patients (Nagaya 2005, Chest) and improved cardiac output in chronic heart failure (Nagaya 2004, Circulation). Small, from one group, not followed by larger confirmatory trials. [5][6]

Graded A (small)

Gastroparesis and ileus

Small of ghrelin and mimetics (e.g. relamorelin, TZP-101) reported faster gastric emptying; larger programmes had mixed results and none reached approval.

Diagnostic GH stimulation

The mimetic macimorelin is approved for diagnosing adult GH deficiency on the strength of validation trials against the insulin tolerance test (Garcia 2018, J Clin Endocrinol Metab). [9]

Metabolism, sleep, mood

Rodent work on glucose, anxiety, sleep and reward. Human data are limited to short infusions.

4Reported side effects and interactions

Literature-reported

Short-term IV and SC ghrelin was well tolerated in trials: transient flushing, warmth, sweating, mild drowsiness, bowel sounds/hunger, and expected hormonal changes — rises in GH, cortisol, ACTH, prolactin and glucose with a fall in insulin. Long-term human safety is not established.

Community-reported

ghrelin itself is seldom used; the ghrelin-mimetic experience (strong hunger, water retention, lethargy, raised fasting glucose) is covered under GHRP-6 and MK-677.

Theoretical. chronic GH/IGF-1 elevation and raised glucose with sustained use; tumour-growth caution shared across the GH axis; ghrelin receptors on some tumours. Reduced insulin secretion is a concern for anyone with impaired glucose handling.

Interactions. additive GH release with GHRH analogues (sermorelin, CJC-1295, tesamorelin); raised glucose may affect glucose-lowering medicines; somatostatin blunts its GH effect.

Markers researchers commonly monitor

Based on ghrelin physiology and GH-axis practice:

Marker	Why it's watched
IGF-1	the integrated marker of GH release over weeks.
Fasting glucose, fasting insulin, HbA1c	ghrelin suppresses insulin and raises glucose directly, on top of GH's effect; the most important safety markers.
Morning cortisol and prolactin	ghrelin raises both modestly, unlike ipamorelin; a baseline shows whether that matters for the individual.
Body weight, appetite log and body composition	the outcomes that matter in cachexia and the things that drift unwanted in healthy users.
Lipid panel	GH and weight change both shift lipids.
Blood pressure and heart rate	ghrelin is a mild vasodilator and inotrope in trials.

Free for everyone. Safety information is never behind a paywall.

5Reconstitution and handling

Research-grade human ghrelin is supplied in microgram-to-milligram vials and is more fragile than most peptides because the octanoyl ester hydrolyses. with sterile or immediately before use where possible; keep cold, protect from light, and discard solutions that have been stored for more than a few days. Doses in trials were weight-based in micrograms per kilogram, so unit maths matters.

Open in calculator, pre-loaded →

6Commonly studied alongside

Ipamorelin (#4), GHRP-6, GHRP-2, hexarelin, MK-677 and anamorelin (its mimetics); CJC-1295 / sermorelin / tesamorelin (GHRH side of the axis); leptin (#119), its counterpart in appetite regulation; GLP-1 agonists such as semaglutide (#3), which act in the opposite direction on appetite.

Informational cross-links. Not stack recommendations.

7Regulatory status by region

Region	Status (checked —)
United States	Ghrelin not FDA-approved. Macimorelin (Macrilen) approved 2017 as a diagnostic. Anamorelin not approved. Ghrelin not on FDA compounding bulk lists †
European Union	Ghrelin not authorised. Macimorelin (Ghryvelin) authorised 2019. Anamorelin refused 2017
United Kingdom	Not licensed; macimorelin licensed as a diagnostic
Australia	Not approved
South Africa	Not registered
Sport	Prohibited by WADA under S2 (growth hormone secretagogues, which explicitly names lenomorelin/ghrelin and its mimetics)

8Open questions

Does des-acyl ghrelin have its own receptor and clinical role?
Whether ghrelin or a mimetic can improve functional outcomes (strength, survival) in cachexia, not just lean mass.
Long-term safety of sustained ghrelin-receptor activation — the question that hangs over every GH .
Ghrelin's role in alcohol and reward behaviour, where antagonists are being studied.

9References

1Kojima M et al. (1999). Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature. PubMed · DOI
2Takaya K et al. (2000). Ghrelin strongly stimulates growth hormone release in humans. J Clin Endocrinol Metab. PubMed · DOI
3Wren AM et al. (2001). Ghrelin enhances appetite and increases food intake in humans. J Clin Endocrinol Metab. PubMed · DOI
4Neary NM et al. (2004). Ghrelin increases energy intake in cancer patients with impaired appetite. J Clin Endocrinol Metab. PubMed
5Nagaya N et al. (2005). Treatment of cachexia with ghrelin in patients with COPD. Chest. PubMed · DOI
6Nagaya N et al. (2004). Effects of ghrelin administration on left ventricular function, exercise capacity, and muscle wasting in patients with chronic heart failure. Circulation. PubMed · DOI
7Temel JS et al. (2016). Anamorelin in patients with non-small-cell lung cancer and cachexia (ROMANA 1 and 2). Lancet Oncol. PubMed
8Müller TD et al. (2015). Ghrelin. Mol Metab (comprehensive review). PubMed · DOI
9Garcia JM et al. (2018). Macimorelin as a diagnostic test for adult GH deficiency. J Clin Endocrinol Metab. PubMed · DOI

References are being resolved to PubMed/DOI identifiers; links search PubMed for the citation until then.

† Being confirmed by our reviewers against current sources.

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11Page history

26 Oct 2026Profile published — awaiting medical review

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