Animal and human studies demonstrated the regulatory function of leptin in nervous system and showed that non-motor manifestations such as cognitive dysfunction of patients with PD as well as mesostriatal and mesolimbic dopaminergic pathways are affected by serum and cerebrospinal fluid (CSF) level of leptin.14-18 On the other hand, both motor symptoms and NMS influence the energy intake and energy expenditure. Here, LEP is linked to Parkinson disease.