The objective of this paper is to review the current evidence of a novel gastric hormone ghrelin. Ghrelin is an endogenous ligand for the growth hormone secretagogue receptor (GHS-R) that potently stimulates growth hormone (GH) release. The discovery of ghrelin opens up a new regulatory system for the GH secretion. Surprisingly, recent studies in rodents suggest that peripherally or centrally administrated ghrelin, independent of GH, decreases fat oxidation and increases food intake and adiposity. In addition, plasma ghrelin levels are lower in obese human subjects. Ghrelin might participate in meal initiation and may signal to the hypothalamus when an increase in the metabolic efficiency is needed. However, the role of ghrelin in the regulation of body weight in humans is unknown. Whether ghrelin's somatotrophic effect surpasses its adipogenic effect in the prolonged administration determines its effect on energy balance. New interesting implications for ghrelin have recently been suggested. For instance, ghrelin's cardiovascular effects might have clinical relevance. Furthermore, ghrelin might be involved in the growth of some neoplasms. In conclusion, ghrelin, a new somatotrophic, orexigenic and adipogenic peptide hormone, links the regulatory systems for growth and energy balance.