A hormone secreted by the beta cells of the pancreas. It regulates the metabolism of carbohydrates, proteins, and fats in the body. Increase in blood glucose stimulates insulin secretion. Insulin, in turn, ensures the absorption of glucose by tissues and stimulates glycogenesis in the liver. During treatment with insulin preparations (due to the possible appearance of antibodies to exogenous insulin), the level of insulinemia varies depending on the concentration of antibodies. In this case, it is better to replace the determination of endogenous insulin levels with the C-peptide test. The value of the insulin-glucose ratio > 0.3 suggests the presence of insulinoma.