Orexins, also named hypocretins, are neuropeptides present in the hypothalamus. The orexin signaling pathway thought to participate in a complex cycle of energy homeostasis,many studies have extended the multifaceted role of orexins to the regulation of peripheral functions either through a central control or direct interaction with peripheral target tissues such as hypophysis, adrenals, GIT or endocrine pancreas. Furthermore, pharmacological intervention directed at the orexin receptors may prove to be an attractive avenue toward the discovery of novel therapeutics for diseases involving dysregulation of energy homeostasis such as obesity and diabetes mellitus. This book, therefore, discuss the possible effects of orexin-A on insulin secretion, the hypothalamo- pituitary-adrenal axis function, and the adrenergic system, as regulators of energy homeostasis, this up- to-date analysis should help medical students, postgraduates, and specially researchers in physiology...