Insulinomas derive from pancreatic beta-cells and are the most common form of functional neuroendocrine tumours of the pancreas with an incidence of 1-4 newly diagnosed cases per 1 million per year. Most are benign and have a diameter of less than 2 cm but in approximately 10% they are malignant (mostly in multiple endocrine neoplasia I patients) and metastasize, preferentially to lymph nodes and liver.

Resection is the therapy of choice and in many cases, the localization can be determined preoperatively.

However, the prognosis remains relatively poor with a 10-year survival of less than 30%.

Another cause of adult hyperinsulinemic hypoglycemia is adult beta cell hyperplasia for which the term “nesidioblastosis” has been resurrected that had been in use for CHI up to the 1980s. It is difficult to exactly determine the incidence of the disease, but it appears that in approximately 5% of the cases of adult hyperinsulinemic hypoglycaemia (AHH) nesidioblastosis may be the underlying pathology while insulinoma is responsible for the majority of cases.