Insulin
Insulin is a peptide hormone produced chiefly by pancreatic beta cells in the islets of Langerhans. It helps maintain glucose balance by promoting glucose uptake in muscle and fat, encouraging storage of glucose as glycogen, and reducing the liver's release of glucose. As a medicine, insulin replaces or supplements the body's hormone when needed. Its isolation for treatment in the early 1920s transformed diabetes care; recombinant methods later enabled large-scale production of human insulin.
Structure and production
Insulin is a protein hormone made mainly by beta cells, which are located in clusters called pancreatic islets. Beta cells produce a precursor called proinsulin and process it into mature insulin. Human insulin contains 51 amino acids arranged in two chains, conventionally called A and B, held together by disulfide bonds. When blood glucose rises, especially after food is absorbed, beta cells release insulin into the bloodstream.
Role in metabolism
Insulin binds to receptors on target cells and helps coordinate how the body uses and stores nutrients. In skeletal muscle and adipose tissue, it promotes glucose uptake; in the liver and muscles, it supports the storage of glucose as glycogen. It also restrains the liver's production and release of glucose. Insulin works alongside other metabolic signals, including glucagon, which generally helps raise blood glucose when it is low. These actions make insulin central to the regulation of energy balance after meals and between meals.
Insulin as a medicine
Insulin treatment supplies hormone that the body does not make in sufficient amounts or cannot use effectively. People with type 1 diabetes need insulin because their pancreas no longer produces enough of it; some people with type 2 diabetes also use insulin as part of treatment. Formulations are grouped by how quickly they begin to work and how long their effects last. Most are delivered by injection or an insulin pump, while inhaled insulin is available in some settings. Because insulin can lower blood glucose too far, hypoglycemia is an important potential adverse effect; treatment choices and dosing require clinical guidance.
Discovery and development
The therapeutic discovery of insulin followed decades of research linking the pancreas with diabetes; the word and the underlying idea predated the Toronto work. In 1921, Frederick Banting and medical student Charles Best began experiments at the University of Toronto with support from physiologist John Macleod. Biochemist James Collip later improved the purification of pancreatic extracts, making human treatment possible. Leonard Thompson received an insulin injection in January 1922; the first preparation had little effect, but better-purified material and subsequent treatment brought marked improvement. The work was collaborative, although the 1923 Nobel Prize in Physiology or Medicine was awarded to Banting and Macleod; they shared their prize money with Best and Collip. In 1978, researchers at City of Hope and Genentech developed a recombinant-DNA method to make human insulin. The U.S. Food and Drug Administration approved Humulin in 1982, the first biosynthetic human insulin product and the first medical product approved in the United States that was derived from recombinant-DNA technology.
Key facts
- Type
- A peptide hormone composed of 51 amino acids in two linked chains.
- Main source in the body
- Beta cells in the islets of the pancreas.
- Primary role
- Helps regulate blood glucose and nutrient storage, including glucose uptake in muscle and fat and glycogen storage in liver and muscle.
- Clinical importance
- Insulin replacement is essential for people with type 1 diabetes and is also used by some people with type 2 diabetes.
- Production milestone
- The FDA approved recombinant biosynthetic human insulin in 1982.
Timeline
1921
Banting and Best began experiments on pancreatic extracts at the University of Toronto, with Macleod's support; Collip later worked to purify the extract.
11 January 1922
Leonard Thompson received an early insulin injection. The first preparation had little effect; improved purification enabled successful subsequent treatment.
October 1923
The first commercial supply of insulin was shipped, and Banting and Macleod received the Nobel Prize in Physiology or Medicine.
1978
Researchers at City of Hope and Genentech developed a method for producing human insulin using recombinant DNA technology.
1982
The FDA approved Humulin, the first biosynthetic human insulin product and the first U.S.-approved medical product derived from recombinant-DNA technology.
Ask about this article
Answers use only “Insulin” and its references, with citations.
References
- 1.INS gene: MedlinePlus Genetics
MedlinePlus Genetics, U.S. National Library of Medicine · other · reliability: high · retrieved 18 October 2026
Supports: Describes insulin production by pancreatic beta cells, glucose transport, and the processing of proinsulin into insulin chains.
- 2.Role of Insulin in Health and Disease: An Update
International Journal of Molecular Sciences; full text archived in PubMed Central, U.S. National Library of Medicine · other · reliability: high · retrieved 18 October 2026
Supports: Peer-reviewed review of insulin structure, secretion, metabolic actions, and roles in glucose regulation.
- 3.Insulin, Medicines, & Other Diabetes Treatments
National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health · other · reliability: high · retrieved 18 October 2026
Supports: Explains the use of insulin in type 1 and type 2 diabetes, formulation classes, delivery methods, and hypoglycemia risk.
- 4.Insulin Basics
American Diabetes Association · other · reliability: high · retrieved 18 October 2026
Supports: Summarizes insulin production by beta cells, its role in glucose use and storage, and the forms and delivery methods of insulin therapy.
- 5.The “miracle” discovery that reversed the diabetes death sentence
Nobel Prize Outreach · other · reliability: high · retrieved 18 October 2026
Supports: Historical account of the Toronto research, Leonard Thompson's treatment, the collaborators' contributions, and the 1923 Nobel Prize.
- 6.Chapter 3: The Making of Insulin
Connaught Fund, University of Toronto · other · reliability: high · retrieved 18 October 2026
Supports: University history documenting the Banting, Best, Macleod, and Collip collaboration and the first successful human treatment in January 1922.
- 7.100 Years of Insulin
U.S. Food and Drug Administration · other · reliability: high · retrieved 18 October 2026
Supports: FDA history of insulin's early production and the development and approval of recombinant biosynthetic human insulin.
- 8.Insulin
Encyclopaedia Britannica · encyclopedia · reliability: high · retrieved 18 October 2026
Supports: Reference overview of insulin's hormone function, glucose regulation, and historical background.
References are suggested by the research engine and may be incomplete. Unverified URLs are omitted rather than guessed.
Article history
- Version 118 October 2026 · EditorCreated by Zapia