Rising thyroid cancer incidence in the world might be related to insulin resistance

Studies have reported an increasing incidence of thyroid cancer worldwide. The reasons are likely related to improved imaging modalities, altered histopathologic criteria for diagnosis of thyroid cancer, and nuclear exposure. However, the classical assumption derived from epidemiological studies is that it should be questioned whether there are other modifiable risk factors contributing to this increased incidence. Insulin resistance (IR), which is a major component of metabolic syndrome (MetS), is associated with cardiovascular disease risk. Furthermore, previous studies have shown a positive relationship between IR and several common adult cancers. Incidence of thyroid cancer is increasing in parallel to the rise of MetS (and thus IR) incidence. In recent reports, patients with IR have larger thyroid volumes and higher risk for formation of thyroid nodules. Additionally, it was also shown that increased prevalence of IR is present in patients with differentiated thyroid carcinoma. It can be hypothesized that a relationship between the IR and thyroid cancer could be one reason for increasing incidence in the world. (C) 2009 Elsevier Ltd. All rights reserved.