Article

Reviews in Endocrine and Metabolic Disorders

, Volume 7, Issue 4, pp 237-249

First online:

Role of endogenous ghrelin in growth hormone secretion, appetite regulation and metabolism

  • Eleni V. DimarakiAffiliated withDepartment of Medicine, Division of Endocrinology and Metabolic Diseases, Evanston Northwestern Healthcare and Northwestern University Feinberg School of Medicine
  • , Craig A. JaffeAffiliated withDepartment of Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical Center and Ann Arbor Veterans Affairs Medical3920 Taubman Center, Division of Metabolism, Endocrinology and Diabetes Email author 

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Abstract

Ghrelin, a 28-amino acid hormone that is acylated post-translation, is the endogenous ligand for the growth hormone (GH) secretagogue (GHS) receptor (GHS-R). The highest concentrations of ghrelin are found in the stomach; however ghrelin peptide is also present in hypothalamic nuclei known to be important in the control of GH and feeding behavior. Exogenous ghrelin potently stimulates pituitary GH release through a mechanism that is dependent, in part, on endogenous GH-releasing hormone. Whether endogenous ghrelin plays a role in the control of GH secretion and growth is not clear and ghrelin deficient animals appear to grow normally. In contrast, experimental animal and clinical data suggest that abnormalities in GHS-R signaling could impact growth. Ghrelin or other GHS are clinically useful for GH-testing and limited data suggest that they might be useful in the treatment of some patients with GH deficiency. Substantial data have implicated ghrelin as an important regulator of feeding behavior and energy equilibrium. Ghrelin has a potent orexigenic effect in both animals and humans and this effect is mediated through hypothalamic neuropeptide Y (NPY) and Agouti-related peptide (AgRP). Appetite simulation coupled with other metabolic effects promotes weight gain during chronic treatment with ghrelin. These metabolic effects are in part mediated through an increase in respiratory quotient (VQ). Presence of ghrelin appears to be necessary for the development of obesity in some animal models. Whether abnormalities in ghrelin signaling are involved in human obesity is not yet known.

Keywords

Ghrelin Somatotropin Growth Obesity Feeding Fasting Appetite Neuropeptides Stomach Review