IL6 and Parkinson disease: The aim of this study is to evaluate the serum levels of systemic inflammatory markers such as neutrophil–lymphocyte ratio (NLR), neutrophil-HDL ratio (NHR), monocyte-HDL ratio (MHR), platelet–lymphocyte ratio (PLR), IL-6, IGF-1, systemic immune-inflammation index (SII), and systemic inflammation response index (SIRI) in patients with PD, and to analyze the relationship between these markers and the clinical stage of the disease as well as its motor and non-motor symptoms.