Insulin Resistance: Any Role in the Changing Epidemiology of Thyroid Cancer?

Abstract

In the past few decades, the incidence of thyroid cancer (TC), namely of its papillary hystotype (PTC), has shown a steady increase worldwide, which has been attributed at least in part to the increasing diagnosis of early stage tumors. However, some evidence suggests that environmental and lifestyle factors can also play a role. Among the potential risk factors involved in the changing epidemiology of TC, particular attention has been drawn to insulin-resistance and related metabolic disorders, such as obesity, type 2 diabetes, and metabolic syndrome, which have been also rapidly increasing worldwide due to widespread dietary and lifestyle changes. In accordance with this possibility, various epidemiological studies have indeed gathered substantial evidence that insulin resistance-related metabolic disorders might be associated with an increased TC risk either through hyperinsulinemia or by affecting other TC risk factors including iodine deficiency, elevated thyroid stimulating hormone, estrogen-dependent signaling, chronic autoimmune thyroiditis, and others. This review summarizes the current literature evaluating the relationship between metabolic disorders characterized by insulin resistance and the risk for TC as well as the possible underlying mechanisms. The potential implications of such association in TC prevention and therapy are discussed.

Keywords: insulin; insulin growth factor; insulin resistance; insulin sensitizers; metformin; obesity; thyroid cancer; type 2 diabetes.

Figure 1

Schematic representation of the possible links between insulin resistance and thyroid cancer (TC). Insulin resistance consequent to metabolic disorders, as well as exposure to endocrine disrupting chemicals (EDCs), genetic factors, and other conditions may affect the risk of TC by inducing or increasing various risk factors.