INS and pancreatic insulinoma: Second, we know from work we have done with human insulinomas (60, 85) - rare, benign proliferative tumors of the beta cell that overproduce insulin and cause hypoglycemia - that many different types of gene variants (single and multiple nucleotide mutations, copy number loss, copy number gain, chromosomal rearrangements, etc.)are associated with human beta cell proliferation in a manner that expands beta cell mass, while also preserving beta cell function (insulin production) so effectively that it leads to hypoglycemia.