Endocrine Abstracts

Background: Larger thyroid volume and nodular thyroid disease were found to be associated with insulin resistance (IR) in patients with type 2 diabetes (T2DM). Similar analyses is lacking in T1DM.

Aims: To check the association between thyroid volume and IR using estimated glucose disposal rate (eGDR) in patients T1DM.

Materials and methods: We included 99 consecutive patients with T1DM aged 29 (mean, S.D.=6) with diabetes duration 13 (6) years. Exclusion criteria were: history of thyroid disease, current treatment of L-thyroxine or anti-thyroid drugs. Anti-thyroid peroxidase (ATPO), anti-thyroglobulin (ATg) antibodies, and anti-TSH receptor antibodies (TRAb) were determined. Assays for TSH and free thyroid hormones (trijodothyronine, fT₃, and thyroxine (fT₄)) were also performed. Thyroid was measured using ultrasonography. IR was assessed using eGDR, calculated according to the formula (24.4−12.97×WHR−3.39×HT−0.60×HbA1c), where WHR -waist-to-hip ratio and HT – history of hypertension (yes=1 and no=0).

Results: The prevalence of thyroid autoimmunity (positivity for ATPO, ATg, or TRAb) in the study group was 31%. Subclinical hypothyroidism was diagnosed in 7%, and overt hypothyroidism in 2% of patients. Mean (S.D.) thyroid volume was 15.6 (6.2) ml in patients with eGDR ≤7.5 (patients with IR) and 11.7 (4.7) ml in patients with eGDR above 7.5 (P=0.002). Thyroid volume correlated inversely with eGDR (r=−0.35, P<0.001). In multivariate linear regression model association between thyroid volume and eGDR was independent from sex, duration of diabetes, BMI, TSH, and presence of thyroid autoimmunity (β: −0.22, P=0.025).

Conclusion: Lower insulin sensitivity is associated with larger thyroid volume in patients with T1DM independently from BMI and signs of autoimmune thyroid disease.