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Islets of Langerhans

Groups of pancreatic cells which make the hormones such as insulin which control the blood sugar levels.

Specialised cells

Cells which are adapted to carry out a specific function in the body

Type 2 diabetes

The pancreas does produce insulin but cells stop responding properly to the insulin. It is often linked to obesity and lack of exercise and taking more exercise, losing weight and eating a carefully balanced diet can often control or even reverse type 2 diabetes.

Type 1 diabetes

Develops when the body does not produce the right amount of insulin or, in some cases, does not produce any at all. It must be treated with daily injections of insulin. People affected also need to manage their diet, eat regularly and plan exercise carefully to balance their energy needs with their food and insulin intake.

Blood sugar

The sugar (glucose) dissolved in the blood; the normal range is 4.0 - 7.8 mmol/l

Amino acid

The basic building blocks of proteins. There are twenty amino acids used, in different combinations, to make every protein required by the human body.


The study of the human body to investigate how a disease or injury lead to death


An endocrine gland which produces insulin


A polysaccharide, (C6H10O5)n, that is stored in the liver and in muscles and can be converted back into glucose when needed by the body.


A type of sugar: a mono saccharide with 6 carbon atoms (a hexose sugar).


A polymer made up of amino acids joined by peptide bonds. The amino acids present and the order in which they occur vary from one protein to another.


A chemical messenger produced by a particular gland or cells of the endocrine system. Hormones are transported throughout the body in the blood stream but they produce a response only in specific target cells


A large organ in the upper abdomen which manufactures, stores and breaks down substances as required by the body


The liquid which leaves your body through the urethra. It contains water, salts urea and other chemicals.


A short piece of DNA which is responsible for the inheritance of a particular characteristic. It codes for the production of a specific protein. Genes occupy a fixed position, called a locus, on a particular DNA molecule.

1922: Insulin

In 1922, the Canadian physiologists Fred Banting and Charles Best announced to the world that they had discovered Insulin and successfully used it to treat diabetes in a human patient. Until then, diabetics would struggle to grow and there was no successful treatment. They would become walking skeletons and die prematurely due to severe weight loss.

An ancient problem

Diabetes mellitus had been known since ancient times. Egyptian writings from as early as 1500BC described a wasting disease in which the sufferer produced sweet-tasting urine. From the 1850's onwards, autopsies of people who had died from diabetes suggested that the problem was caused when the pancreas did not function properly. Many physicians speculated that specialised cells, called the islets of Langerhans, produced a chemical that allowed the body to regulate its blood sugar level. Diabetes was caused when this chemical was not produced.

Animal experiments show the solution

Fred Banting (right) and Charles Best with one of their diabetic dogs

Banting and Best worked in the University of Toronto. They removed the pancreas from dogs which then developed diabetes. Their experiments may seem cruel today but without them, insulin would never have been found as the treatment for diabetes.

New methods of testing blood sugar levels allowed Banting and Best to accurately determine the effects of their treatments. They struggled to purify the chemical hormone produced by the pancreas and extracted many compounds from the islets of Langerhans. These were injected into the diabetic dogs to try and find the hormone that would reverse their diabetes.

An early advert for insulin from 1928

Initially the injections were very impure and often had fatal side-effects. A team of researchers were recruited and eventually they were able to make an extract from the islets of Langerhans that was pure enough to try on a human patient. In May 1922, fourteen-year-old Leonard Thompson was successfully treated in Toronto Hospital with the extract that they called insulin. In 1928, Oskar Wintersteiner proved that insulin was a protein.

We now know that insulin allows the cells of the body to take in sugar from a digested meal. The liver is especially important in the process of regulating the body's blood sugar level. Insulin enables the liver to take in sugar (glucose) after a meal and store it as glycogen. This is used later to return glucose to the blood when blood sugar levels begin to fall.

You can find out more about insulin in Hormones and their effects.

Meeting the demand for insulin

News of Banting and Best's success spread quickly and soon their laboratory was unable to meet the demand for the new wonder drug.

Commercial preparation of insulin began by extracting it from the pancreas of slaughtered cows and pigs. Early insulins were injected three or four times a day, just before each meal. More long-acting insulins were developed so that the need to inject so often was reduced.


In 1955 the Nobel Prize-winner Frederick Sanger found the amino acid sequence of human insulin. This allowed a human insulin gene to be made which was then used to genetically engineer bacteria that could produce large amounts of highly pure human insulin. This is now the main type of insulin available, both short and long-acting versions are used. In 2016 there were 3.6 million people in the UK with diabetes. 10% of these have Type 1 diabetes where the body produces little or no insulin; Type 2 diabetes is much more common; in this type of diabetes the body does not produce enough insulin or body cells do not respond to the insulin produced.

You can learn more about what causes diabetes in our Diabetes topic.

An old syringe and modern pen device for injecting insulin
(courtesy of Novo Nordisk)
Today a regular supply of insulin can be delivered throughout the day using a pump