Endogenous hyperinsulinism, including autoimmune insulin hypoglycemia (antibodies against insulin or the insulin receptor; Hirata ́s disease), insulinoma (or insulinomatosis with insulin expressing monohormonal endocrine cell clusters (IMECCs); a case with recurrent hypoglycemia even after total pancreatectomy was recently reported [245]), nesidioblastosis/NIPHS, and PGBHH have been discussed. The gene discussed is INSR; the disease is hyperinsulinism.