Which organ secretes insulin?

• A. Pancreas
• B. Adrenal gland
• C. Liver
• D. Stomach

Answer: (A)

Insulin is a hormone produced by the pancreas, specifically by the beta cells in the islets of Langerhans. When blood glucose rises, these cells release insulin into the bloodstream, signaling muscles and adipose tissue to take up glucose and prompting the liver to store excess glucose as glycogen. The pancreas has an endocrine role (hormone secretion) and an exocrine role (digestive enzymes); insulin comes from the endocrine portion. The other organs listed do not secrete insulin: the adrenal gland makes hormones like adrenaline and cortisol, the liver does not produce insulin (it responds to it and stores glucose), and the stomach mainly secretes acid and other stomach hormones. Therefore, insulin is secreted by the pancreas.