Insulin

Insulin's isolation in 1921 Toronto transformed diabetes from an invariably fatal diagnosis into a manageable chronic condition. Frederick Banting, a surgeon with a hunch and limited research experience, partnered with student assistant Charles Best to achieve what established physiologists had failed to do: extract the pancreatic hormone that regulates blood sugar.

The adjacent possible had been building since the 1860s, when researchers linked the pancreas to diabetes. By 1901, scientists had named the hypothetical substance 'insulin' and knew it came from the islets of Langerhans. Multiple teams had tried to extract it, but pancreatic digestive enzymes destroyed the hormone during extraction. The key insight Banting brought was procedural: tie off the pancreatic duct to cause the enzyme-producing cells to atrophy, then extract insulin from the remaining islet tissue.

The summer of 1921 saw Banting and Best working in a borrowed laboratory while Professor J.J.R. Macleod, their supervisor, vacationed in Scotland. Their extraction worked on diabetic dogs; by January 1922, they treated the first human patient, 14-year-old Leonard Thompson, at Toronto General Hospital. Thompson lived another 13 years, dying of pneumonia rather than diabetes.

The commercialization unfolded with remarkable speed. Eli Lilly began industrial-scale production in 1922, using slaughterhouse pancreases from pigs and cattle. The path dependence established by animal-derived insulin would persist for six decades until recombinant DNA technology enabled synthetic human insulin in the 1980s.

The Nobel Prize followed quickly—Banting and Macleod shared the 1923 award in Physiology or Medicine, sparking controversy that continues to this day. Banting, furious that Macleod was recognized while Best was not, split his prize money with Best. Macleod shared his with James Collip, the biochemist who had purified the crude extract.

Insulin became the first protein to have its amino acid sequence determined (Frederick Sanger, 1955 Nobel Prize) and the first human protein produced through genetic engineering (1978). The arc from Banting's hypothesis to today's insulin pumps and continuous glucose monitors demonstrates how a single medical breakthrough can spawn decades of consequential innovations.