RAGE polymorphisms and oxidative stress levels in Hashimoto's thyroiditis.

BACKGROUND: Polymorphisms of the receptor for advanced glycation end products (RAGE) gene have been studied in various autoimmune disorders, but not in Hashimoto's thyroiditis. Also, increased oxidative stress has been described in patients with Hashimoto's thyroiditis. The aim of this study was to investigate the possible role of two common RAGE polymorphisms (-429T>C, -374T>A) in Hashimoto's thyroiditis; in parallel, we studied oxidative stress levels. MATERIALS AND METHODS: A total of 300 consecutive euthyroid women were examined and classified into three groups: Hashimoto's thyroiditis with treatment (n = 96), Hashimoto's thyroiditis without treatment (n = 109) and controls (n = 95). For a rough evaluation of oxidative stress, total lipid peroxide levels in serum were measured. The -429T>C AluI and -374T>A MfeI polymorphisms of RAGE were studied in genomic DNA. RESULTS: Significant association of the RAGE system with Hashimoto's thyroiditis was found only with regard to the prevalence of the -429T>C, but not with -374T>A polymorphism. The levels of oxidative stress were significantly elevated in Hashimoto's thyroiditis patients under treatment. Further analysis demonstrated that an oxidative stress cut-off value of 590 µmol/L is associated with an increased risk of progression of Hashimoto's thyroiditis from euthyroidism to hypothyroidism; this risk is further increased in carriers of the RAGE -429T>C polymorphism. CONCLUSIONS: Our findings indicate that both examined risk factors may be implicated in the occurrence of Hashimoto's thyroiditis, but this covers only a fraction of the pathophysiology of the disease.

The effect of obesity and dietary habits on oxidative stress in Hashimoto's thyroiditis

Objective: Increased oxidative stress has been described in patients with Hashimoto's thyroiditis (HT). The aim of the present study was to investigate whether high oxidative stress is further influenced by obesity and dietary habits in euthyroid women with HT. Methods: Two hundred eighteen consecutive euthyroid women with HT were studied and separated in two groups; 102 with thyroxine replacement and 114 without. For the evaluation of oxidative stress, total lipid peroxide levels in serum (TOS) were measured and recoded as 'high TOS' vs 'medium/low TOS'. The type of food and consumption frequency were recorded. Two binary variables were considered; normal vs low fruit consumption and daily vs sporadic vegetable consumption. Results: 'High TOS' was more frequent in women under thyroxine replacement (31.4% vs 14.7%, OR = 2.7, 95% CI: 1.4­5.2). The prevalence of 'high TOS' was higher among overweight/obese women compared to women with normal BMI (30.4% vs 12.5%, OR = 3.1, 95% CI: 1.5­6.4). Low fruit consumption was associated with increased 'high TOS' prevalence (30.6% vs 12.9%, OR = 3.0, 95% CI: 1.4­6.2). Sporadic vegetable consumption was associated with increased 'high TOS' prevalence compared to daily consumption (29.9% vs 13.5%, OR = 2.7, 95% CI: 1.3­5.7). The examined risk factors were independent and additive in their effect on TOS. At least three risk factors had to be concomitantly present for the likelihood of 'high TOS' to be significantly elevated. Conclusions: Oxidative stress is increased in women with HT under thyroxine replacement. Nevertheless, normal BMI, daily fruit and vegetable consumption, all contribute in maintaining oxidative stress at low levels.