Discovery of insulin

Discovery of insulin
Name	Discovery of insulin
Caption	Early insulin vials and syringes used in clinical administration
Date	1921–1922
Location	Toronto, Ontario, Canada
Participants	Frederick Banting, Charles Best, John Macleod, James Collip, Eli Lilly and Company, University of Toronto
Outcome	Isolation of pancreatic extract capable of treating diabetes mellitus; development of therapeutic insulin

Discovery of insulin

The discovery of insulin refers to the isolation and development of a pancreatic extract that effectively treated diabetes mellitus in humans, achieved principally in Toronto in 1921–1922. This breakthrough connected laboratory physiology, clinical medicine, pharmaceutical manufacturing, and academic institutions, rapidly transforming the prognosis of diabetes from fatal disease to manageable chronic condition. The work involved collaborations and disputes among clinicians and scientists that reverberated through 20th century biomedical research, pharmaceutical industry practices, and Nobel Prize history.

Background and early research on diabetes

By the late 19th and early 20th centuries, physicians such as Sir William Osler, Elliott P. Joslin, and pathologists like Oskar Minkowski and Joseph von Mering had linked pancreatic pathology to diabetes; Minkowski and von Mering demonstrated pancreatic removal induced diabetes in dogs at the University of Strasbourg. Researchers including Paul Langerhans had identified pancreatic islets later named after him, and investigators such as E. L. Scott, E. G. L. Williams, and George Oliver explored pancreatic extracts and their physiological effects at institutions like Cambridge University and University College London. The therapeutic concept of a pancreatic "internal secretion" was pursued by laboratories under figures such as Eugen Steinach, Nicolae Paulescu at the University of Bucharest, and researchers in Vienna and Berlin, while clinical diabetologists including Harold R. Himsworth and Frederick Menzies were advancing diagnostic and dietary management at hospitals like Royal Victoria Hospital and Guy's Hospital. Early attempts to produce a stable, non-toxic pancreatic extract were hindered by proteolytic enzymes and inadequate purification techniques available to laboratories such as Rockefeller Institute and pharmaceutical firms including Parke, Davis.

The Toronto experiments and isolation (1921–1922)

In the summer of 1921 at the University of Toronto, surgeon Frederick Banting and medical student Charles Best began experiments in the laboratory of physiologist John Macleod using a technique of ligating pancreatic ducts in dogs to degenerate exocrine tissue and preserve the insulin-producing islets; contemporaneous methods had roots in techniques from St. Bartholomew's Hospital and practices described by investigators at University of Vienna. Banting and Best's crude pancreatic extracts were first tested in pancreatectomized dogs and later in patients admitted to the Toronto General Hospital. Biochemist James Collip joined to refine purification, applying protein chemistry from laboratories influenced by Frederick Sanger and methods resembling those used at University of Cambridge and University of Edinburgh to reduce impurities and endotoxin-like reactions. Clinical application occurred when a 14-year-old patient, Leonard Thompson, received the partially purified extract in January 1922 at Toronto General Hospital, resulting in dramatic reduction of glycosuria and ketonuria after Collip's biochemical improvements.

Contributions of key researchers (Banting, Best, Collip, Macleod)

Frederick Banting conceptualized the duct-ligation strategy and initiated the surgical and experimental program; his clinical insight linked pancreatic islet function to glucose regulation. Charles Best performed day-to-day experiments, prepared extracts, and assisted with physiological assays at Macleod's laboratory bench. John Macleod provided laboratory space, experimental guidance, and intellectual oversight, securing support from the University of Toronto and the Connaught Laboratories infrastructure, and liaising with clinicians like Mayo Clinic consultants and hospital administrators. James Collip applied biochemical extraction and purification techniques derived from protein chemistry traditions at institutions such as McGill University and University of Toronto, producing a formulation suitable for human therapy and facilitating transfer to manufacturers such as Eli Lilly and Company and Connaught Laboratories. Collectively, these figures interacted with contemporaries including Harvey Cushing, E. G. Young, and industrial partners like Herman Banting (relative collaborator in production logistics).

Clinical trials, commercialization, and production

Following successful clinical responses at Toronto General Hospital, the University of Toronto and industrial partners moved to scale production. Eli Lilly and Company collaborated to industrialize insulin manufacture, adopting purification protocols developed by Collip and quality control informed by regulatory practices emerging from agencies modeled on Food and Drug Administration-era principles. The Connaught Laboratories produced public health-oriented supplies distributed to hospitals and clinics across Canada, the United States, and Europe. Early clinical trials and compassionate use extended to institutions such as Massachusetts General Hospital, Royal Infirmary of Edinburgh, and Charité – Universitätsmedizin Berlin. Patent and licensing decisions—controversially minimal at the University of Toronto—enabled rapid dissemination and low-cost access, shaping relationships between academia, private industry, and philanthropic bodies like the Rockefeller Foundation.

Scientific impact and subsequent developments

The insulin breakthrough propelled endocrinology as a distinct specialty, influencing researchers at Harvard Medical School, Johns Hopkins University, and Karolinska Institute to investigate hormonal regulation, receptor biology, and glucose metabolism. It stimulated biochemical advances in peptide isolation, amino acid sequencing exemplified later by Frederick Sanger's insulin work, and laid groundwork for synthetic and recombinant approaches at laboratories including Genentech and firms such as Novo Nordisk and Eli Lilly and Company that later developed long-acting analogs and recombinant human insulin. Clinical practice evolved with contributions from Elliott P. Joslin and diabetology centers at Toronto Western Hospital and Mayo Clinic, leading to protocols for insulin dosing, subcutaneous administration, and innovations such as insulin pens and continuous infusion inspired by engineering from Massachusetts Institute of Technology collaborations.

Controversies and recognition (Nobel Prize and credit disputes)

Recognition culminated in the 1923 Nobel Prize in Physiology or Medicine awarded to John Macleod and Frederick Banting; Banting, protesting perceived omission of Charles Best, shared his prize money with Best, while Macleod shared his award money with James Collip. Debates persisted among historians and scientists regarding priority claims involving Nicolae Paulescu of the University of Bucharest—who published on pancreatic extracts earlier—and other contributors from laboratories in France, Romania, and Austria, as well as the roles of institutional credit and commercial partners like Eli Lilly and Company. The episode influenced later policies on attribution, patenting, and university-industry collaboration at institutions such as Stanford University and Massachusetts Institute of Technology and remains a case study in scientific ethics, credit allocation, and the sociology of biomedical discovery.

Category:History of medicine