FNDC5 and obesity due to melanocortin 4 receptor deficiency: Irisin is a multifunctional protein secreted by skeletal muscles, first discovered and named by Bostrom et al.11 Irisin is a matter of extensive study due to its association with chronic metabolic diseases such as obesity and diabetes.25-27 Circulating irisin is related to various disease states, including but not limited to, type 2 diabetes, CKD, and hypothyroidism.28-31 Irisin may also serve as a biomarker for acute myocardial infarction and a clinical prognostic indicator for acute pancreatitis.16,18 The present study shows reduced serum levels of irisin in patients with ischemic AKI.