Thyroid volume and nodules in patients with impaired fasting glucose and type 2 diabetes mellitus

Abstract

Background. The relationship between insulin resistance and thyroid nodules is not clearly understood. Insulin resistance is associated with increased thyroid volume and nodule prevalence in patients with metabolic syndrome. Metformin commonly used in patients with type 2 diabetes mellitus (T2DM) might possibly alter thyroid function and morphology. Data on the association of thyroid morphology and abnormal glucose metabolism are limited. This prospective study was carried out to evaluate impaired fasting glucose (IFG) and T2DM as a risk factor for increased thyroid volume and nodule prevalence in iodine-deficient area. Materials and methods. This was a prospective case-control study in patients with IFG and T2DM. Data were gathered on all patients newly diagnosed with IFG and T2DM between January 2018 and December 2020. Sixty-five patients with IFG and 52people with T2DM were randomly matched for age, gender, and smoking habits with 38 subjects with normal glucose metabolism. Serum thyroid-stimulating hormone (TSH) was evaluated, and thyroid ultrasonography was performed in all participants. Results. Mean TSH level in the T2DM group (2.1±0.9 mIU/l) was significantly higher than in controls (1.4±0.7 mIU/l) and in the IFG group (1.5±0.8 mIU/l) (p<0.001 for both). Thyroid autoantibody levels were within normal limits and did not differ significantly between 3 groups. Mean thyroid volume was significantly higher in the IFG (16.1±4.2 cm3) and T2DM groups (19.4±5.2 cm3) compared to controls (11.9±3.7cm3). In the T2DM group, there was a positive correlation between TSH and body mass index (r=0.43; p<0.01), and between TSH and waist circumference (r=0.37; p<0.01). The number of patients with thyroid nodules was also higher in the IFG (46.2%) and T2DM groups (63.1%) than in controls (18.4%). Conclusions. The results suggest that patients with impaired glucose metabolism and type 2 diabetes mellitus have significantly increased thyroid volume and nodule prevalence.