Insulin is a hormone, synthesized and secreted by Pancreas, which is and elongated structure about 15 cm in length, 100 gm is weight and is situated behind the stomach. The pancreas consists of two parts-the Exocrine and Endocrine. The Exocrine part constituents about 80 to 85% of the total gland. The total weight of endocrine pancreas in the adult however does not exceed 1-1.5 gm. The exocrine part secretes various enzymes which are needed for digestion. The endocrine, part consists of “ Islets of Langerhans” which are made up of several types of cells. They are alpha cells (also called A cells) which secrete glucagons; the beta cells (also called B Cells) which secrete insulin; delta cells (also called D cells) which secret somatostatin.

Insulin was first discovered in 1922 by Banting and Best. Its chemical structure was worked out in 1956 by Sanger. Steiner discovered by Proinsulin in 1967.

Because of the Insulin secretion, blood sugar remains within the normal limits.


  • Our body needs glucose to produce energy, in order to carry out body’s various vital functions. Glucose is obtained from the carbohydrates mainly Cereals and starch such as wheat, Rice Fruit, etc. Insulin helps the entry of glucose into all cells of the body. However, glucose entry in liver, brain, R.B.C.’s is largely, independent of insulin. Hence, insulin while present within the cells of the body, converts the glucose into energy, which is required to perform major body functions. But when Insulin is insufficient or lacking, then the glucose is not transported to the cells and no energy is produced.
  • Along with entry of glucose into the cells, insulin also helps in Glycogen sis, i.e. synthesis of glycogen from glucose, in liver and muscle cells. This stored glycogen will act as a source of reserve energy. In between the meals, when the cells need energy, the stored glycogen is transformed back into glucose and is utilized by the cells.
  • Insulin inhibits the synthesis of glucose from sources other than Carbohydrates (known as Neoglucogenesis). This decreases the blood glucose level.
  • Insulin also helps in the entry of amino acids into cells and their synthesis into protein.
  • Insulin promote lipogenesis (i.e., synthesis of triglyceride) and thus facilitates entry of fatty acids within the cells.

Therefore, in the absence of Insulin maintenance of blood sugar level is hampered, leading to hyperglycaemia, and severe consequences.