Endocrine Abstracts

Background: Hashimoto thyroiditis (HT) is the most common autoimmune disease and patients may present different levels of thyroid dysfunction. The association between hypothyroidism and cardiovascular events is well established. However, it remains unclear how mild thyroid dysfunction, autoimmunity and chronic inflammation in HT contribute to an increased cardiovascular risk in euthyroid patients and in subclinical hypothyrodism. Therefore, this study aims to assess insulin resistance, lipid panel and low-grade inflammation in HT patients.

Methods: A total of 228 patients with HT were enrolled and divided into 3 groups, accordingly to TSH levels – TSH 0.35–2.49 µUI/ml, TSH 2.5–4.94 µUI/ml and TSH>4.94 µUI/ml. We assessed thyroid function tests, thyroid antibodies, lipid profile, insulin resistance indexes [homeostasis model assessment insulin resistance (HOMA-IR), quantitative insulin sensitivity check index (QUICKI), insulinogenic index (IGI), whole body insulin sensitivity index (WBISI) and hepatic insulin sensitivity index (HISI)], high-sensitivity C-reactive protein (hs-CRP), vitamin B12, folic acid and homocysteine. Statistical analysis was made using one-way ANOVA, Student’s t-test, Pearson’s correlations and multiple linear regression.

Results: 93.9% of our population were women and mean age was 47.06 ± 15.4 years. No significant statistical differences were found between groups, regarding age, sex and body mass index. The group TSH > 4.94 µUI/ml, in comparison to the group TSH 2.5–4.94 µUI/ml, showed significant higher values of HOMA-IR (3.77 ± 2.93 vs 1.95 ± 1.25, P < 0.001) and inferior values of QUICKI (0.48 ± 0.13 vs 0.70 ± 0.39, P = 0.049) and HISI (41.73 ± 29.03 vs 79.84 ± 63.72, P = 0.026). The group with TSH 2.5–4.94 µUI/ml, in comparison to the group TSH 0.35–2.49 µUI/ml, presented significant higher levels of Apolipoprotein B (ApoB) (102.14 ± 33.885 vs 97.64 ± 21.001, P = 0.036). In the total group, positive correlations were found between TSH and both triglycerides (r = 0.206, P = 0.002) and HOMA-IR (r = 0.209, P = 0.002). Positive correlations were found between thyroid peroxidase antibodies levels and total cholesterol (r = 0.166, P = 0.013), LDL-cholesterol (r = 0.173, P = 0.01), triglycerides (r = 0.148, P = 0.027), ApoB (r = 0.190, P = 0.006) and HOMA-IR (r = 0.141, P = 0.033). Thyroglobulin antibodies correlated positively with triglycerides (r = 0.140, P = 0.036). Hs-CRP correlated positively with IGI (r = 0.156, P = 0.024) and negatively with WBISI (r = −0.177, P = 0.010).

Conclusions: HT patients with mild thyroid disfunction present a more atherogenic lipid profile and higher resistance to insulin action. Thyroid autoimmunity also seems to be related to insulin resistance, to a less favorable lipid panel and low-grade inflammation. These findings demonstrate the importance of screening for cardiovascular comorbidities in these patients to provide an early diagnosis and better treatment decisions.