Insulin's 85th anniversary—An enduring medical miracle

Abstract In 1922, the discovery of insulin led to a revolution in diabetes management. Since then, many improvements have been made to insulin preparations: early preparations of bovine and porcine insulins were purified and their duration of action prolonged, giving rise to the introduction of Neutral Protamine Hagedorn (NPH) insulin and monocomponent insulins. Then, with the advances in genetic engineering in the 1980s, it became possible to produce recombinant human insulin. Nowadays, modern molecular biology techniques enable the production of insulin analogues, which have several advantages over human insulin preparations including a reduced risk of hypoglycaemia. Insulin delivery is still predominantly via subcutaneous injections, but alternative routes of insulin administration are being investigated. Pulmonary delivery has emerged as the most feasible option thus far but oral delivery is an ultimate goal, although basic problems of insulin stability in the gut and absorption from the gastrointestinal tract still need to be resolved. The availability of a true artificial pancreas by means of a closed-loop system, linking continuous glucose monitoring with insulin-pump technology, would also constitute a significant advance, but major technological problems still need to be overcome.