Evaluation of interrelationships between thyroid function, insulin resistance, lipid profile and inflammation in autoimmune thyroiditis
Celestino Neves1, Marta Alves1, Miguel Pereira1, Isolina Pimentel1, Ema Carvalho1, Renata Ramalho2, Carmo Palmares2, Cristina Guimarães2, João Pedro Ramos2, Davide Carvalho1, Luís Delgado2 & José Luís Medina1
Background: Autoimmune thyroiditis (AIT) is associated with increased risk of cardiovascular disease.
Objective: To evaluate the interrelationships between insulin resistance (IR) and other cardiovascular risk factors, such as high sensitivity CRP (C reactive protein) and homocysteine in patients with AIT.
Patients and methods: We analysed thyroid function, anti-thyroid antibodies, BMI, indices of IR, such as HOMA-IR, HISI (Hepatic Insulin Sensitivity Index), WBISI (Whole-Body Insulin Sensitivity Index), IGI (Insulinogenic Index), total cholesterol (TC), HDL-cholesterol, LDL-cholesterol, triglycerides (TG), ApoB, ApoA1, Lp(a), homocysteine, CRP, folic acid and B12 vitamin levels in 260 patients with AIT, 93.8% female, with a mean age of 47.2±14.8 years old and BMI 27.5±5.6 kg/m2. Each patient was submitted to an OGTT (75 g glucose) with measurements of glucose, insulin and C-peptide each 30 min, during 2 h. Statistic analysis was done with ANOVA and Pearson correlation tests. Results are expressed as mean±SD. A P<0.05 was considered significant.
Results: Analitical results are presented: TSH 3.680±11.877 UI/ml; FT3 2.94±0.99 pg/ml; FT4 1.52±1.84 ng/dl; C-peptide 2.62±1.04 ng/ml; TC 203.58±41.12 mg/dl; TG 117.27±83.87 mg/dl; HDL-cholesterol 57.08±14.87 mg/dl; ApoA1 145.24±29.71 mg/dl; ApoB 97.02±24.36 mg/dl; Lp(a) 28.21±32.22 mg/dl; CRP 0.47±0.83 mg/dl. We found positive significant correlations between IGI and anti-TPO (r=0.179; P=0.005), C-peptide (r=0.463; P<0.001), TG (r=0.227; P<0.001), CRP (r=0.162; P=0.02) and TSH (r=0.126, P=0.048) levels. HISI results positively correlated with TSH (r=0.173; P=0.006). We also detected significant negative correlations between WBISI and TG (r=−0.191; P=0.003), and CRP (r=−0.181; P=0.008) levels.
Conclusion: The interrelationships between thyroid function, insulin resistance, lipid profile and inflammation may explain the increased cardiovascular risk associated with AIT.