Leptin is an endogenous peptide that binds leptin receptors; it is involved in feeding behavior and energy homeostasis. Leptin exhibits anorexigenic, antihypertensive, and neuroprotective activities. Leptin induces secretion of α-melanocyte-stimulating hormone (α-MSH) and gonadotropin-releasing hormone (GnRH). In obese and hypertensive rats, leptin decreases blood pressure. This peptide also inhibits myocardial muscle contractility and modulates bone growth and resorption. Additionally, leptin may be involved in the development of atherosclerosis. In animal models of Alzheimer’s disease, leptin decreases levels of tau and amyloid-β (Aβ), improving cognitive performance.