Serum proinsulin

Human proinsulin is a precursor of insulin. It is composed of insulin and C-peptide. It has dual immunological activity and can bind to both insulin antibodies and C-peptide antibodies. Proinsulin is synthesized and secreted by islet β cells, which are mainly catabolized in the kidney. Under physiological conditions, only a very small amount of proinsulin is released into the blood. Under pathological conditions, the islet beta cells of the islets release proinsulin, which increases the level of proinsulin in the blood.