Leptin is a 16-kDa adipokine encoded by the obese gene. It helps maintain normal body weight and energy homeostasis. Leptin expression is regulated by insulin, glucocorticoids and leptin itself. Levels of circulating leptin are proportional to body fat mass and fluctuate based on changes in nutritional states. Leptin binds to and activates the long form of leptin receptors (LepRb) expressed in many regions of the brain. The hypothalamus is the main Leptin target and mediates its anti-obesity action. Leptin also has other physiologic and pathologic functions resembling those of cytokines which include the regulation of hematopoiesis, angiogenesis, wound healing, inflammation, and immune responses