Endocrine Abstracts

Introduction: Thyroid dysfunction has been associated with cardiovascular events since it worsens atherogenesis, insulin resistance and dyslipidemia. Thyroid hormones and adipokines interact with each other to regulate metabolism. The impact of thyroid dysfunction on adipokines serum levels remains controversial.

Objective: To evaluate the interrelations between thyroid function and cardiovascular risk factors as insulin resistance, lipid profile, inflammatory markers and adipokines, in autoimmune thyroiditis patients.

Methods: 60 patients with autoimmune thyroiditis were evaluated and tree groups were defined based on TSH level: TSH between 0.4 and 4.0 μUI/ml (50 individuals), TSH between 0.4 and 2.5 μUI/ml (29 individuals) and TSH higher than 4.0 μUI/ml and normal levels of free T4 (FT4) and free T3 (FT3) (10 individuals). We measured thyroid function and autoimmunity, lipid profile, serum homocysteine, vitamin B12, folic acid, high-sensitivity C-reactive protein, adiponectin, resistin, PAI-1 (plasminogen activator inhibitor-1), VCAM-1 (vascular cell adhesion molecule 1), ICAM-1(intercellular adhesion molecule 1), and insulin resistance markers comprising the HOMA-IR and WBISI (Whole-Body Insulin Sensitivity Index). A 75-g OGTT was performed in the morning (before 11 AM), and blood samples were obtained every 30 min for 120 min for measurements of plasma glucose, insulin, and C-peptide. Fisher’s exact test, Kruskal-Wallis test, One-way ANOVA test and Pearson’s correlations were performed for statistical analysis.

Results: In our sample, median age was 51.0 (32.3–59.8) years. There were no significant differences regarding median age or median BMI between groups. Patients with TSH>4.0 presented higher HOMA-IR when compared to those with patients with TSH 0.4–4.0 (2.1 (1.4–3.0) vs 1.02 (0.41–2.45), P=0.042) and lower WBISI (46.4 (27.7–72.7) vs 60.6 (42.8–124.3), P=0.042). In all sample, TSH was positively correlated with HOMA-IR (r=0.317, P=0.014) and negatively with WBISI (r=−0.311, P=0.027). We observed positive correlation with resistin and fasting C-peptid (r=0.440, P=0.001). FT3 was negatively correlated with PAI-1 (r=−0.328, P=0.011). In TSH 0.4–4.0 group, we found positive correlations between TSH and both HOMA-IR (r=0.404, P=0.004) and resistin (r=0.420, P=0.002). FT3 was negatively correlated with PAI-1 (r=−0.311, P=0.030). In TSH 0.4–2.5 group, FT3 was positively correlated with homocysteine (r=0.441, P=0.021) and negatively correlated with PAI-1 (r=−0.440, P=0.019). In TSH>0.4 group, we observed positive correlation between FT4 and HDL (r=0.768, P=0.009).

Conclusions: Autoimmune thyroiditis is associated with an increased cardiovascular risk. This association is complex and involves multiple factors. We found significant interrelationships between thyroid function, lipid profile, insulin resistance, homocysteine, resistin and PAI-1.