The islets of Langerhans are the endocrine part of the pancreas. These are the clusters of prism-shaped cells that release a hormone known as insulin which is required for the conversion of excess sugars into glycogen in the liver and muscles. Another hormone released by this gland is glucagon which is an antagonist of insulin. It activates liver glycogenolysis (breakdown of glycogen) and increases blood sugar level. Deficiency of insulin leads to one of the most common hormonal disorders called diabetes mellitus.