A change in carbohydrate metabolism is called impaired glucose tolerance. This term refers to the ability of the body to convert the excess glucose entering the plasma into reserve substances. Thus, excess glucose does not accumulate in the blood. If the incoming carbohydrates, splitting to glucose, circulate in the blood for a long time in an increased amount, this can lead to diabetes. Certain organic substances and biochemical processes regulate the metabolism of carbohydrates in the body. What kind of peptide hormone is involved in reducing the concentration of glucose in the blood?