Objectives: Patients with thyroid dysfunction due to AITD have been found to have increased oxidative stress. Possible associations of oxidative stress with thyroid hormone (TH) and thyroid autoantibodies (ThAb) levels in euthyroid patients with autoimmune thyroiditis have not been adequately studied. We examined possible associations of oxidative stress markers with TH levels and with the presence of ThAb in euthyroid women with Hashimotos thyroiditis (with or without T4 replacement).
Methods: A total of 298 women were examined: 208 women with ThAb (+) (mean age 47.9±11.5, range 2269 years, group 1: 100 euthyroid and group 2: 108 on T4 replacement). 90 women with ThAb (−) and negative family history for AITD served as controls (mean age 43.6±12.9, range 1967). The type of food, the frequency and the way of cooking was filled and the weekly diet antioxidative score (DAS) was calculated. Peroxide lipid levels (index of oxidative stress, TOS) and the calculated diet antioxidative score were estimated.
Results: DAS was inversely associated with TOS (r=−0.11, P=0.049). Mean DAS was lower in women with anti-TPO (+) vs anti-TPO (−): (167.9±47.5 vs 181.7±55.0, P=0.031, MannWhitney U test). Multivariate logistic regression analysis showed that TPO positivity was significantly associated with DAS (P=0.044 or 0.995) when age, TSH and smoking were taken into account. No difference in TOS according to TPO positivity was found. TOS was positively associated with T4 (r=0.137, P=0.001). This association remained significant when TSH, anti-TPO positivity and age were taken into account. TOS was positively associated with T3 levels (r=0.190, P=0.001); however this was no longer significant in the multivariate analysis. No significant difference concerning TOS was found between women on or without thyroxine replacement therapy.
Conclusions: Diet with lower antioxidant score may be a predisposing factor for the development of thyroid autoimmunity (TPO positivity). TOS is positively associated with TH levels even in the normal range as has been previously shown in the hyperthyroid state. No association of anti-TG Abs with oxidative parameters was found.