Objective: We aimed to investigate the effects of oxidative stress in the pathhogenesis and progression of thyroiditis in patients with Hashimotos thyroiditis whose aetiopathogenesis includes environmental and genetic factors.
Methods: 80 patients (40 euthyroid and 40 subclinical hypothyroidism) older than 18 years with newly diagnosed Hashimotos thyroiditis and not yet on any treatment were enrolled. Patients were followed up for 9 months. Blood sample was drawn at diagnosis for thyroid function tests and oxidative stress parameters. Total antioxidant status (TAS), total oxidative status (TOS), paraoxonase 1 (PON1), arylesterase, and total thiol (total SH) were measured by colorimetric method. The ratio of serum TOS level and TAS level gave the oxidative stress index. TSH, free thyroxine (fT4), anti-thyroid peroxidase (anti-TPO), and anti-thyroglobulin (anti-Tg) were measured by ECLIA method.
Results: Total SH level was found to be higher in the euthyroid group as compared to the subclinical hypothyroidism group (P=0.019). TAS, TOS, OSI, PON, and arylesterase levels were similar in the two groups (P>0.05). At 9 months of follow-up, overt hypothyroidism developed in 14 patients. Patients with overt hypothyroidism tended to have significantly higher average TOS and OSI levels at diagnosis (P<0.001) and significantly higher anti-Tg and anti-TPO levels at hypothyroidism development (P<0.05) than those who did not develop overt hypothyroidism. Multivariable Cox regression analysis showed TSH level (HR=1.348, P<0.001), fT4 level (HR=0.481, P=0.017), and OSI ratio (HR=2.349, P<0.001) to be independent predictors for the development of overt hypothyroidism in euthyroid patients and those with subclinical hypothyroidism.
Conclusion: Higher levels of autoantibodies and oxidative stress in patients developing overt hypothyroidism shows that oxidative stress plays a major role in the pathogenesis and progression of autoimmune thyroiditis.