The novel peptide hormone ghrelin has recently been recognized as an important co-regulator of growth hormone secretion and energy homeostasis. The significance of ghrelin for obesity and cachexia as well as in the regulation of growth processes is the subject of ongoing basic research as well as clinical studies. It is our goal to emphasize the critical significance of the hypothalamic signaling modalities induced by ghrelin for a better understanding of how this novel hormone affects energy balance and metabolism.