# Ghrelin > The only hormone that makes you hungry — a stomach peptide, uniquely fatty-acid-modified, that drives appetite and also releases growth hormone. - Also known as: Lenomorelin, the hunger hormone, acyl-ghrelin - Class: Peptide Hormones, Growth Hormone - FDA approved: No - Canonical page: https://americanpeptide.com/catalog/ghrelin ## Overview Ghrelin is a 28-amino-acid hormone made mainly in the stomach and best known as the body’s principal hunger signal — levels rise before meals and fall after eating. It is biochemically unusual: it requires an octanoyl (C8 fatty-acid) group attached to its third residue to be active, the only known hormone modified this way. Beyond appetite, ghrelin is a potent releaser of growth hormone, which links it to the secretagogue peptides elsewhere in this catalog. Almost every appetite hormone tells you to stop eating; ghrelin is the one that tells you to start. Secreted by the stomach when it is empty, it rises in the run-up to a meal, drives the sensation of hunger through hypothalamic feeding circuits, and falls once you have eaten. That makes it the orexigenic counterweight to satiety hormones like leptin, amylin, and the incretins — and a natural target for the opposite therapeutic goal: stimulating appetite in wasting conditions. Its defining oddity is chemical. Ghrelin is the only human hormone known to carry an O-acyl fatty-acid modification — an octanoyl group esterified to the serine at position 3 by a dedicated enzyme (ghrelin O-acyltransferase, GOAT). Without that fatty acid the peptide cannot activate its receptor. This makes the GOAT enzyme an unusual drug target and the acylation a defining feature of how the hormone is studied and measured (acyl- versus des-acyl ghrelin). Ghrelin’s second action is on growth hormone: it is the endogenous ligand of the growth-hormone secretagogue receptor, the same receptor hit by synthetic GHRPs such as ipamorelin and hexarelin found elsewhere in this catalog — so ghrelin is, in effect, the natural template those drugs imitate. Therapeutically the interest runs toward appetite stimulation: ghrelin-receptor agonists (anamorelin, relamorelin) have been studied for cancer cachexia and gastroparesis, making the hunger hormone a candidate where too little appetite is the problem. ## Mechanism Agonist at the growth-hormone secretagogue receptor (GHSR-1a). The octanoyl modification (added by the enzyme GOAT) is required for receptor binding. Activation stimulates appetite via hypothalamic NPY/AgRP neurons and triggers growth-hormone release from the pituitary. ## Chemistry | Property | Value | | --- | --- | | Molecular weight | 3370.9 Da | | CAS number | 304853-26-7 | ## Sequence ``` GSSFLSPEHQRVQQRKESKKPPAKLQPR (Ser3 O-octanoylated; human) ``` ## Research areas Studied in: Appetite regulation, Growth hormone regulation, Cachexia, Energy balance, Peptide hormones. Guides on this site: - [Growth Hormone & Body Composition](https://americanpeptide.com/research-areas/growth-hormone-axis): Secretagogues studied for GH release, IGF-1, and body composition. - [Peptide Hormone Synthesis](https://americanpeptide.com/research-areas/peptide-hormones): How hormone sequences are turned into pure, stable, manufacturable synthetic drugs. ## Key research - Appetite — the principal circulating hunger signal; rises before meals and stimulates feeding via hypothalamic NPY/AgRP neurons. - Growth hormone — the endogenous ligand of GHSR-1a, the receptor targeted by synthetic secretagogues (ipamorelin, hexarelin). - Cachexia — ghrelin-receptor agonists (anamorelin) studied to stimulate appetite and lean mass in cancer-related wasting. - Unique acylation — the only human hormone requiring an octanoyl fatty-acid modification (via GOAT) for activity; the enzyme is a distinctive drug target. - Energy balance — acts opposite to satiety hormones such as leptin and amylin in body-weight regulation. ## Storage, handling & synthesis **Synthesis.** The standout synthetic challenge in this class: activity requires an O-octanoyl ester on the Ser3 hydroxyl — the only such acylation among human hormones (installed biologically by ghrelin O-acyltransferase, GOAT). Standard solid-phase synthesis assembles the 28-mer, but installing and preserving the acid- and base-labile octanoyl ester demands orthogonal side-chain protection and a deliberately mild final deprotection/cleavage, since the unmodified by-product (des-acyl ghrelin) is inactive. The acylation is the purity-defining step, and acyl-vs-des-acyl ratio is the assay that matters most. ## FAQs ### What is ghrelin? A stomach-derived hormone that is the body’s main hunger signal — it rises before meals to stimulate appetite and falls after eating. It also triggers growth-hormone release. ### Why is ghrelin chemically unusual? It is the only known human hormone that needs a fatty-acid (octanoyl) group attached to one of its residues to work. The enzyme that adds it, GOAT, is a distinctive potential drug target. ### How is ghrelin related to growth-hormone peptides? Ghrelin is the natural ligand of the growth-hormone secretagogue receptor — the same receptor that synthetic GHRPs like ipamorelin and hexarelin activate. Those drugs essentially mimic ghrelin’s growth-hormone action. ### Is this medical advice? No — this is a research and educational reference, not dosing guidance. ## Latest research Recent trials and publications mentioning Ghrelin, pulled automatically from ClinicalTrials.gov and PubMed (unfiltered search results, refreshed daily). ### Recent trials - [Bariatric Endoscopic Antral Myotomy Combined With Fundal Gastric Mucosal Ablation](https://clinicaltrials.gov/study/NCT07612527) — RECRUITING · PHASE2 · NCT07612527 - [Determining the Effect of Food Ordering on Blood Glucose In Gestational Diabetes Mellitus (DEFI-GDM)](https://clinicaltrials.gov/study/NCT06896799) — RECRUITING · NA · NCT06896799 - [Metabolic Flux Analysis in Metabolic Dysfunction-Associated Steatotic Liver Disease](https://clinicaltrials.gov/study/NCT07760909) — NOT_YET_RECRUITING · NA · NCT07760909 - [Effect of Probiotics on Appetite Regulation in Adults With Overweight/Obesity](https://clinicaltrials.gov/study/NCT07715955) — RECRUITING · NA · NCT07715955 - [Metabolic and Cognitive Parameters Following Partial Sleep Deprivation](https://clinicaltrials.gov/study/NCT01823263) — COMPLETED · NA · NCT01823263 - [Cardiometabolic Effects of the Recommended Daily Pecan Intake Dose](https://clinicaltrials.gov/study/NCT07696403) — NOT_YET_RECRUITING · NA · NCT07696403 --- Source: AmericanPeptide.com — https://americanpeptide.com/catalog/ghrelin Data license: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Attribution: AmericanPeptide.com. Research reference only — computational and educational content, not medical advice.