Physicians can identify children or young adults who are likely to develop type I, or juvenile-onset, diabetes. These people have a relative with the disease, and their blood carries a telltale antibody against islet cells in the pancreas. These cells produce insulin, the hormone needed to metabolize sugars. The presence of the antibody signals that the immune system may be primed to attack the islet cells.
Tests in animals and in small groups of people have suggested that giving insulin to those who are diabetes-prone might forestall the development of type I diabetes. Although such preemptive tactics are tantalizing, a study by researchers at the University of Miami Medical School suggests they just don't work.