Endocrine Abstracts

Background: Increasing incidence of thyroid cancer may be attributable to sensitive diagnostic tools as well as changes in exposure to certain environmental factors. Type 2 diabetes mellitus (DM) reaches high prevalence worldwide. DM is a risk factor for many chronic disorders including cardiovascular disease and cancer. Insulin resistance (IR) is a fundamental aspect of the etiology of DM and compensatory hyperinsulinemia could promote cancer growth. The association between DM and thyroid cancer is inconclusive.

Methods: Case–control prospective study in 698 randomly selected patients without history/treatment of thyroid disease in iodine sufficient area. The patients were screened for DM, underwent thyroid ultrasound and laboratory tests. The patients were assigned to group of prediabetes (PDM) (n=53; 7.6%), DM (n=64; 9%) and non-DM (NDM) (n=581). FNA (fine needle aspiration biopsy) was carried out in 224 patients.

Results: Thyroid size (ml) in DM 15.1 (9.59–21.57), PDM 13.35 (8.94–17.88), NDM 10.87 (7.94–16.2); (P=0.001; after adjustment for age P=0.062). TSH (mUI/l) in DM 2.4 (1–6.7), PDM 1.2 (0.7–2.45) and NDM 1.6 (0.85–3.6) (P=0.65). PDM/DM were in 40% of patients diagnosed by our screening. FNA Bethesda I (n=22; 9.8%), II (n=169; 75.5%), III (n=13; 5.8%), IV (n=7; 3.1%), V (n=8; 3.6%), VI (n=5; 2.2%). Histological examination was done in 37 patients, 19 findings were malignant (2.72%). Rate of thyroid malignancy was similar in PDM/DM 3.42% vs NDM 2.58%. In both groups the most common type of thyroid tumor was papillary carcinoma (50%; P=0.668). Advanced differentiated thyroid carcinoma and other histological types including poorly differentiated tumors were just in NDM group. TSH correlated negatively with thyroid size in all study groups (r=−0.474; P=0), and with thyroid nodule size just in NDM (r=−0.357; P=0). This relation remained identical after exclusion of patients with Graves-Basedow thyrotoxicosis (r=−0.459; P=0). Just in NDM and PDM groups, the thyroid size was positively correlated with HOMA IR (r=0.303; P=0.001 vs r=0.414; P=0.013), BMI (r=0.201; P=0 vs r=0.330; P=0.025) and C-peptide (r=0.266; P=0.004 vs r=0.437; P=0.009).

Conclusion: In the most insulin resistant subjects, diabetic and prediabetic group, we did not observe significantly increased risk of thyroid cancer. Thyroid cancer types with poorer prognosis were observed just in NDM. Thyroid gland is larger in DM, but ageing is essential part of this growth. TSH represents major stimulus of thyroid growth. However, other growth factors besides TSH must be involved.