Editing Frederick Banting (section)

=== Isolation of insulin ===
{{Main|Insulin#History of study}}

[[File:C. H. Best and F. G. Banting ca. 1924.png|thumb|left|[[Charles Best (medical scientist)|Charles Best]] and Banting, c. 1924]]
An article he read about the [[pancreas]] piqued Banting's interest in [[diabetes]]. Banting had to give a talk on the pancreas to one of his classes at the [[University of Western Ontario]] on November 1, 1920, and he was therefore reading reports that other scientists had written.{{Sfn|Bliss|1992|p=51–52}} Research by [[Bernhard Naunyn|Naunyn]], [[Oskar Minkowski|Minkowski]], [[Eugene Lindsay Opie|Opie]], [[Edward Albert Sharpey-Schafer|Sharpey-Schafer]], and others suggested that diabetes resulted from a lack of a protein [[hormone]] secreted by the [[islets of Langerhans]] in the pancreas. Schafer had named this putative hormone "insulin". The hormone was thought to control the metabolism of sugar; its lack led to an increase of sugar in the blood which was then excreted in urine. Attempts to extract insulin from ground-up pancreas cells were unsuccessful, likely because of the destruction of the insulin by the [[proteolysis]] [[enzyme]] of the pancreas. The challenge was to find a way to extract insulin from the pancreas prior to its destruction.<ref name="Nobel"/>

[[Moses Barron]] published an article in 1920 which described experimental closure of the [[pancreatic duct]] by [[ligature (medicine)|ligature]]; this further influenced Banting's thinking. The procedure caused deterioration of the cells of the pancreas that secrete [[trypsin]] which breaks down insulin, but it left the islets of Langerhans intact. Banting realized that this procedure would destroy the trypsin-secreting cells but not the insulin. Once the trypsin-secreting cells had died, insulin could be extracted from the islets of Langerhans. Banting discussed this approach with [[John Macleod (physiologist)|John Macleod]], professor of physiology at the University of Toronto. Macleod provided experimental facilities and the assistance of one of his students, [[Charles Best (medical scientist)|Charles Best]]. Banting and Best, with the assistance of biochemist [[James Collip]], began the production of insulin by this means.<ref name="Nobel"/>

As the experiments proceeded, the required quantities could no longer be obtained by performing surgery on living dogs. In November 1921, Banting hit upon the idea of obtaining insulin from the fetal pancreas. He removed the pancreases from fetal calves at a [[William Davies Company|William Davies slaughterhouse]] and found the extracts to be just as potent as those extracted from the dog pancreases. By December 1921, he had also succeeded in extracting insulin from the adult pancreas.<ref name="rosenfeld2002">{{cite journal |last1=Rosenfeld |first1=Louis |title=Insulin: Discovery and Controversy |journal=Clinical Chemistry |date=December 1, 2002 |volume=48 |issue=12 |pages=2270–2288 |doi=10.1093/clinchem/48.12.2270 |pmid=12446492 |url=http://clinchem.aaccjnls.org/content/48/12/2270 |language=en |issn=0009-9147|doi-access=free |url-access=subscription }}</ref> Pork and beef would remain the primary commercial sources of insulin until they were replaced by [[Insulin#Synthesis 2|genetically engineered bacteria]] in the late 20th century. On January 11, 1922, the first ever injection of insulin was given to 14-year-old Canadian [[Leonard Thompson (diabetic)|Leonard Thompson]] at [[Toronto General Hospital]]. In spring of 1922, Banting established a private practice in Toronto and began to treat diabetic patients. His first American patient was [[Elizabeth Hughes Gossett]], daughter of U.S. Secretary of State [[Charles Evans Hughes]].<ref name="bliss1982">{{cite book|last1=Bliss|first1=Michael|title=The Discovery of Insulin|date=1982|publisher=University of Chicago Press|location=Chicago|isbn=978-0226058979|url=https://archive.org/details/discoveryofinsul00blis}}</ref>

Banting and Macleod were jointly awarded the 1923 Nobel Prize in Physiology or Medicine. Banting split his half of the Prize money with Best, and Macleod split the other half of the Prize money with James Collip.