Leptin is a 16 Kilodalton protien produce that is encoded by the obese gene. It is also referred to the obesity gene product or adipose tissue-specific OB gene product referring to its exclusive site of secretion, the white fat adipocytes. Once released in the circulation, leptin lowers body weight by decreasing appetite and altering metabolic processes.The Hypothalamus appears to be the major target tissue for the hormone sinve leptin receptors are present within the appetite control centers of this region and are of very high affinity, also they are present in other tissues namely the skeletal muscle, kidneys, lungs, the pancreatic islets suggesting that this peptide exerts effects on energy expenditure through peripheral sites. They obesity (OB) gen protein, knows as leptin has an impoertant role in regulation of appetite and energy balance in human, therfore it is involved in the pathogenesis of poor appetite, low food intake, cachexia in the variable debilitaing diseases as diabetes milletus, liver cirrhosis, pulmonary tuberculosis and cancer.