What Is Ghrelin? Benefits, Research & Safety

Ghrelin was discovered in 1999 by Masayasu Kojima and colleagues in Japan. They identified it as the endogenous ligand for the growth hormone secretagogue receptor (GHS-R), which had been known since the development of synthetic growth hormone secretagogues. The name "ghrelin" derives from "ghre," a Proto-Indo-European root for "grow," reflecting its growth hormone-releasing activity. The discovery explained how synthetic GH secretagogues like GHRP-6 worked—they mimicked an endogenous signal. The surprising finding was that ghrelin was primarily produced in the stomach, not the brain. This established a gut-brain signaling axis connecting nutritional status to hypothalamic appetite centers. Research quickly revealed ghrelin's potent orexigenic (appetite-stimulating) effects. Ghrelin levels rise before meals (preprandial) and fall after eating, acting as a meal initiation signal. This positioned ghrelin as a potential target for obesity treatment. Studies in conditions like anorexia nervosa, cachexia, and post-surgical patients have explored both the pathophysiology of ghrelin dysregulation and therapeutic potential of ghrelin or ghrelin agonists. The ghrelin-growth hormone connection has also led to interest in ghrelin for age-related conditions, though the complexity of ghrelin biology has made therapeutic development challenging.