Background: In Hashimotos thyroiditis, chronic inflammation and autoimmunity increases oxidant radicals and cause oxidative stress. However, the effect of levothyroxine therapy on the oxidant and antioxidant systems is not known in overt hypothyroidism. Therefore, we sought to investigate the effect of levothyroxine sodium therapy on oxidative stress in patients with Hashimoto thyroiditis and overt hypothyroidism.
Materials and methods: 36 patients (nine males and 27 females) with a diagnosis of Hashimotos thyroiditis and overt hypothyroidism older than 18 years and not yet on any therapy were enrolled. Blood samples were taken at diagnosis and after 6 months following treatment with levothyroxine for measurements of TSH, free thyroxine (fT4), anti-thyroid peroxidase (anti-TPO), anti-thyroglobulin (anti-Tg), and oxidative stress parameters. TSH, fT4, anti-TPO, and anti-Tg levels were measured using the ECLIA method. Total antioxidant status (TAS), total oxidative status (TOS), paraoxonase 1 (PON1), aryesterase, and total thiol (total SH) levels were measured using the colorimetric method. Oxidative stress index (OSI) was obtained from the ratio of TOS and TAS levels.
Results: TSH, anti-TPO, and anti-Tg levels decreased after treatment (P<0.05) while fT4 level increased (P<0.05). TAS level increased after treatment (1.5±0.2 vs 1.7±0.3, P=0.030) while TOS level decreased (6.5±1.9 vs 4.4±1.3, P=0.012). OSI ratio also decreased after treatment (4.3±2.3 vs 2.7±1, P=0.003). Total SH level increased after treatment (442.8±63.8 vs 470.3±30.1, P=0.034), but no significant change was observed in arylesterase and log(PON) levels.
Conclusion: Levothyroxine treatment was found to have positive effects in terms of thyroid antibodies and oxidative stress parameters in patients with Hashimotos thyroiditis. More studies are needed to understand whether this effect of levothyroxine is due to increase of antioxidant molecules and induction of enzyme synthesis or reduction of inflammation.