In 1916, Sir Edward Sharpe Shaffer discovered insulin secreted by the human pancreas. In 1921, Canadian physiologists Banting and Best described the antidiabetic role of insulin. In 1923, Eli Lilly collected and marketed insulin from the pancreas of pigs and cows. In 1954, Frederick Sanger discovered the amino acid sequence and chemical structure of human insulin. In 1977, Itakura and his colleagues first synthesized two chains of human insulin. In 1980, Novo Industry of Denmark converted pig insulin into 99% pure human insulin. In 1981, scientists at Hope National Medical Center in California produced pure human insulin. In 1982, Eli Lilly commercially produced human insulin called Humulin. Currently, companies such as Genintech, Novo Industries, Biogen, Eli Lilly etc. are commercially marketing pure human insulin.