Where does insulin that diabetics inject come from?

The first successful insulin preparations came from cows (and later pigs). The pancreatic islets and the insulin protein contained within them were isolated from animals slaughtered for food in a similar but more complex fashion than was used by our doctor and med-student duo. The bovine (cow) and porcine (pig) insulin were purified, bottled, and sold.

Bovine and porcine insulin worked very well (and still do!) for the vast majority of patients, but some could develop an allergy or other types of reactions to the foreign protein (a foreign protein is a protein which is not native to humans). In the 1980's technology had advanced to the point where we could make human insulin. The advantage would be that human insulin would have a much lower chance of inducing a reaction because it is not a foreign protein (all humans have the exact same insulin, so we do not "see" this as a foreign protein).

The technology which made this approach possible was the development of recombinant DNA ... more.

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