Chronic hypoglycemia, which occurs with insulin-secreting tumors, leads to marked β cell atrophy,27 whereas chronic hyperglycemia can lead to β cell hyperplasia and hypertrophy.28,29 Using partial pancreatectomy to create a model of hyperglycemia in rats, we found that individual β cell size increased by 85%.29 Increases in glucose levels stimulate replication within a day,30 and over time lead to hyperplasia. This evidence concerns the gene INS and Hyperglycemia.