The classification of diabetes mellitus: A conceptual framework

Diabetes is the extreme manifestation of a spectrum of conditions in which the balance of insulin secretion and insulin action (or IR) has been altered. Loss of euglycemia is caused by relative insulin deficiency in the presence of IR, or by absolute insulin deficiency. There are related conditions in which an alteration of IR or β-cell dysfunction exists, but because of compensation (increased insulin secretion or increased insulin sensitivity) glucose homeostasis has not been lost. Patients with these conditions are at increased risk of developing diabetes if the compensatory mechanisms fail. There are multiple causes of IR and of β-cell failure. The elucidation of these causes and the attention to the different degrees of insulin deficiency and IR allow for better diagnosis, treatment, and prevention of diabetes and its related conditions.