A decrease in circulating irisin levels was not only associated with cardio- and cerebrovascular conditions and diseases (myocardial infarction, HF, hypertension, atherosclerosis, vascular dementia, stroke), osteoporosis, T2DM, obesity, and CKD but also demonstrated its discriminatory ability for the prognosis of their natural evolution [33,34,35,36,37,38]. The gene discussed is FNDC5; the disease is obesity due to melanocortin 4 receptor deficiency.