The stunned beta cell: a brief history.

beta cell dysfunction is sufficient to cause hyperglycemia; beta cell loss is not necessary but, if severe, can be sufficient and may be accompanied by intrinsic beta cell dysfunction. Clinical testing can differentiate beta cell capacity from beta cell glucose sensitivity but cannot ascribe either to relative changes in beta cell mass versus function. However, longitudinal and intervention studies indicate that beta cell glucose insensitivity (stunning) closely tracks with hyperglycemia and is, at least in part, reversible. Rescuing stunned beta cells is a key therapeutic target.