Overview of the Physiology and Pathophysiology of Leptin With Special Emphasis on its Role in the Kidney Abstract The adipocyte product leptin is a pleiotropic adipokine and hormone, with a role extending beyond appetite suppression and increased energy expenditure. This review summarizes the biology of the leptin system and the roles of its different receptors in a multitude of cellular functions in different organs, with special emphasis on the kidney. Leptin's physiological functions as well as deleterious effects in states of leptin deficiency or hyperleptinemia are emphasized. Chronic hyperleptinemia can increase blood pressure through the sympathetic nervous system and renal salt retention. The concept of selective leptin resistance in obesity is emerging, whereby leptin's effect on appetite and energy expenditure is blunted, with a concomitant increase in leptin's other effects as a result of the accompanying hyperleptinemia. The divergence in response likely is explained by di ...