Relation of prediabetes and type 2 diabetes mellitus to thyroid cancer

OBJECTIVE: Patients with type 2 diabetes (T2DM) generally experience a higher incidence of cancer. However, the association between T2DM and thyroid cancer is inconclusive. METHODS: Case-control prospective study, where 722 patients were screened for T2DM and prediabetes (PDM) and underwent thyroid ultrasound and biochemical tests. The patients were assigned to groups of PDM (n = 55), T2DM (n = 79) or a non-diabetes group (NDM) (n = 588). Fine-needle aspiration biopsy was carried out in 263 patients. Histological examinations were done for 109 patients after surgery, with findings of 52 benign (BS) and 57 malignant tumors (MS). RESULTS: Thirty-three percent of patients with T2DM and especially PDM were newly diagnosed by our screening: 6.5% with T2DM and 72% with PDM, respectively. The percentage of thyroid cancers did not significantly differ between the groups (χ(2) test = 0.461; P = 0.794). Relevant positive thyroid predictors for T2DM (t-statistic = 25.87; P < 0.01) and PDM (21.69; P < 0.01) contrary to NDM (−26.9; P < 0.01) were thyroid volume (4.79; P < 0.01), thyroid nodule volume (3.25; P < 0.01) and multinodular thyroid gland (4.83; P < 0.01), while negative relevant predictors included the occurrence of autoimmune thyroid disease (AITD) (−2.01; P < 0.05). CONCLUSION: In general, we did not observe an increased risk for thyroid cancer in the diabetic and prediabetic groups in comparison to controls, in spite of well-established increased risk for other malignancies. Structural and benign changes such as larger and multinodular thyroid glands, in comparison to autoimmune thyroid disease, are present more often in diabetics.