Royal Society of Biology logo Insulin Important hormone that regulates blood sugar levels Heritage Lottery Fund logo Biotechnology and Biological Sciences Research Council logo

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The hormone insulin is produced by the pancreas to regulate blood sugar levels. Now a vital treatment for patients with diabetes, insulin was not used as medication until 1922 and the development of this drug for medical use took many years.

Patients with type 1 diabetes regularly self-administer insulin to regulate their blood sugar levels. But before insulin was available, the condition was life-threatening and sufferers often died within a short space of time. All that was known that the symptoms of diabetes could be improved by reducing sugar intake, and that the pancreas was damaged in patients with the condition.

The first real advance was in 1869, when Paul Langerhans found clusters of cells within the part of the pancreas that produces digestive juices. The cells Langerhans had discovered turned out to be the insulin-producing beta cells, and were later called the islets of Langerhans in his honour.

In 1889, Oscar Minkowski and Joseph von Mering showed that removing the pancreas from a dog caused it to get diabetes; therefore, the pancreas must produce a secretion to regulate glucose levels.

In 1901, Eugenie Opie linked the islet cells to diabetes, but no further progress was made until 1920. Dr Frederick Banting convinced Professor John Macleod at the University of Toronto to support his laboratory study of diabetes, and recruited Charles Best as an assistant. In 1921 they began their ground-breaking experiments.

Firstly, they removed the pancreas from a dog, which developed diabetes. They then removed the pancreas from a second, healthy dog, ground it up and filtered it to produce “isletin”, and injected this into the diabetic dog. Miraculously, the substance seemed to work and the dog’s blood glucose levels fell; with a few such injections a day, it remained healthy. Banting and Best quickly had to upgrade their work, and started using cows to provide the pancreases they needed. They also added Bertram Collip to their team, who was extremely important in purifying the extract, which was now called “insulin”.

It was not long before the team wanted to test the purified filtrate on humans, and began by injecting themselves. In 1922, Leonard Thompson, a 14 year old boy with type 1 diabetes, became the first patient to be successfully treated with insulin.

In 1923 Banting and Macleod were awarded a Nobel Prize; however, they felt strongly that Best and Collip should have been similarly honoured, and shared their prize money with them.

With the relief of the symptoms of his disease, and with the increased strength and vigor resulting from the increased diet, the pessimistic, melancholy diabetic becomes optimistic and cheerful. Insulin is not a cure for diabetes; it is a treatment."

Sir Frederick Banting, Nobel Prize Lecture, 1923

In 1958, Fred Sanger also received a Nobel Prize for determining the chemical structure of insulin, which allowed it to be chemically synthesised years later. By the 1980s synthetic insulin, which caused fewer adverse reactions than the animal-derived hormone, was widely distributed to patients. Although insulin does not cure diabetes, it has changed the course of this disease so that patients can now lead a normal life, something that would previously have been unimaginable.