Human ghrelin is a 28-amino acid peptide synthesized mainly by endocrine cells of the stomach, but also expresses in other organs. Ghrelin promotes the release of growth hormone, adrenocorticotropic hormone and prolactin. Ghrelin has multiple paracrine, autocrine and endocrine effects on the regulation of food intake, energy homeostasis, gastrointestinal function, cardiac contractility and output, apoptosis, inflammation, and immune system. Ghrelin can also pass through the blood brain barrier (BBB) and activate the vagus nerve system in the brain.
Human ghrelin has been administered as an infusion or a bolus to human subjects participating in more than 100 clinical studies, including healthy volunteers and patients with obesity, prior gastrectomy, cancer, pituitary disease, diabetes, and eating disorders. These studies have reported that administration of human ghrelin is safe with low-to-none toxicity and side effects.