Endocrine Abstracts

Aim: To evaluate the relationship between autoimmune thyroiditis (AIT), subclinical hypothyroidism (SCH) and cardiovascular risk factors.

Patients and methods: We recorded thyroid function tests, BMI, insulin resistance markers comprising the homeostasis model assessment for insulin resistance (HOMA-IR and HOMA-B), the quantitative insulin sensitivity check index (QUICKI), hepatic insulin sensitivity index (HISI), whole-body insulin sensitivity index (WBISI), insulinogenic index (IGI) and the levels of total cholesterol (TC), HDL, LDL-cholesterol, triglycerides (TG), apolipoprotein B (ApoB), ApoA1, lipoprotein (a) (Lp(a)), homocysteine, CRP (C-reactive protein), folic acid and vitamin B12 in 186 subjects with AIT in euthyroid state, and in 69 subjects with AIT and SCH. A 75-g OGTT was performed in the morning and blood samples were obtained for measurements of plasma glucose, insulin, and C-peptide. Statistical analysis was performed with logistic regression and Spearman correlations. Data are expressed by mean±S.D. Statistical significance was considered for a bilateral value of P<0.05.

Results: Ninety-four percent of studied subjects were female. Mean age and BMI were similar in both groups. Patients with higher levels of total cholesterol (OR=1.008; P=0.03), CRP (OR=1.684; P=0.04) or anti-thyroglobulin antibodies (OR=1.002; P=0.02) have an increased likelihood of having SCH. In the total group, we observed a positive correlation between TSH, CPR (r=0.13; P=0.04) and HOMA-IR (r=0.17; P=0.02). We found also a positive correlation between FT₃ and HDL-cholesterol (r=0.16; P<0.01) and between FT₄ and IGI (r=0.22; P<0.01). TSH levels correlated negatively with HISI (r=−0.17; P=0.02) and WBISI (r=−0.17; P=0.02) in the total group. In the euthyroid group, there was a positive correlation between FT₃ and HDL-cholesterol (r=0.17; P=0.03) and between FT₄ and IGI (r=0.25; P<0.01). In the group with SCH, FT₃ correlated negatively with homocysteine (r=−0.36; P=0.01), and HISI (r=−0.30; P=0.04), and the levels of FT₄ correlated negatively with anti-TPO (r=−0.28; P=0.02).

Conclusions: The interrelations between thyroid function, lipid profile, CPR and insulin-resistance demonstrate an increase of cardiovascular risk in subclinical hypothyroidism due to autoimmune thyroiditis.