There are many possible causes of hypoglycemia; among them are the following: prolonged starvation, especially combined with physical exertion; insulin hypersecretion, e.g., in pancreatic insulinoma or pancreatic islet hyperplasia; deficiencies of hormones with effects antagonistic to insulin, e.g., glucocorticosteroids in adrenal insufficiency; a more severe form of hypothyreosis; and some liver diseases, especially glycogen storage diseases. This evidence concerns the gene INS and pancreatic insulinoma.