The following have been proposed as the main mechanisms underlying insulin resistance: (1) genetic variation leading to abnormal insulin structure and biological activity; (2) insulin and post-insulin receptor defects in target tissue; and (3) increases in substances that antagonize the physiological role of insulin, such as catecholamines, growth hormone, glucagon, insulin antibodies, glucocorticoids, and insulin receptor antibodies. This evidence concerns the gene GCG and Insulin resistance.