Change in fasting plasma glucose (A), 2 h post-oral glucose tolerance test (B), and homeostasis model assessment (HOMA-B) insulin secretion (C) during the 16-year follow-up in the Whitehall II study. Of the 6,538 people studied, diabetes developed in 505. Time 0 was taken as the diagnosis of diabetes or as the end of follow-up for those remaining normoglycemic. Redrawn with permission from Tabák et al. (80).
Normally, blood glucose levels are tightly controlled by insulin, a hormone produced by the pancreas. Insulin lowers the blood glucose level. When the blood glucose elevates (for example, after eating food), insulin is released from the pancreas. This release of insulin promotes the uptake of glucose into body cells. In patients with diabetes, the absence of insufficient production of or lack of response to insulin causes hyperglycemia. Diabetes is a chronic medical condition, meaning that although it can be controlled, it lasts a lifetime.