Type 2 Diabetes, Obesity and Their Relation to the Risks of Thyroid Cancer.

Abstract

Objective: patients with type 2 diabetes (T2DM) and obesity are generally known to have increased risk of various types of cancer, though studies addressing associations between T2DM/obesity and thyroid cancer are inconclusive. The aim of our study was to evaluate the risk of thyroid cancer focusing on diabetic patients under conditions of euthyroid status. A retrospective study in 184 patients was performed. Three cohorts were established according to tumor histology: malignant (M), benign (B) and low-risk carcinoma (MB). Fisher's exact test and Kruskal-Wallis one-way ANOVA of ranks were used for statistical analysis. The M (39.1 %), B (57.6 %) and MB (3.3 %) cohorts had comparable age (p=0.4), BMI (p=0.452), glycaemia (p=0.834), Hb1AC (p=0.157) and HOMA-IR (p=0.235). T2DM patients had larger thyroid gland volumes (28.8 vs 17.6 mL;p=0.001) compared to the cohort with normal glucose tolerance. Compared to women, men had more frequently present distal metastases (p=0.017), minimally invasive disease (p=0.027), more advanced staging (p=0.01) and positive pathogenic mutations in the TERT gene (p=0.009);these results were also significant for the diabetic male cohort (p=0.026). Type 2 diabetes and obesity are not risk factors for thyroid cancer, but a subgroup of males seems to have thyroid cancers of poorer prognosis. In general, diabetic patients with insulin resistance and hyperinsulinemia are also prone to have a goiter.

Key words: Thyroid cancer, Type 2 diabetes, Obesity, Thyroid nodule, Insulin resistance.