Szosland and Lewński, in their publication, define insulin resistance as a state of reduced sensitivity or reactivity of target tissues to the metabolic actions of circulating insulin. They indicate that insulin resistance can be selective, when it covers only some directions of insulin action, e.g. only its effect on glucose removal in the liver. Plasma insulin levels are constantly changing under several physiological stimuli, and the threshold values for the diagnosis of IO are strictly defined. Impaired insulin action can occur as a result of disturbances at three levels: • prereceptor (insulin antibodies, damaged insulin molecule), • receptor (insulin receptor defects, anti-receptor antibodies) • post-receptor (deregulated intracellular pathways).Source: Szosland, Konrad & Lewiński, Andrzej. (2018). Insulin resistance – “the good or the bad and ugly”. Neuro endocrinology letters. 39. 355-362.