ROLE OF REACTIVE OXYGEN SPECIES IN INDUCED HYPOTHYROID GOITERS AND HYPERTHYROIDISM IN RATS

In the thyroid, hydrogen peroxide (H2O2), produced superoxide (O-2(.-) ) by superoxide dismutase (SOD), is used by thyroid peroxidase to synt hesise hormones. The excess H2O2 is detoxified by catalase (CAT) and g lutathione peroxidase (GPx). Hormone synthesis being low in the hypofu nctioning gland, reactive oxygen species (ROS) may accumulate. In hype rthyroidism, the situation may be reversed. We have monitored antioxid ant status (SOD, CAT, GPx and reduced glutathione (GSH), and lipid per oxidation (LP)) in rat thyroid tissue. Hypothyroid goitres (PTU, 0.075 %, 18 weeks) showed SOD significantly reduced by 11% and a 16-42% elev ation in all the other parameters. In rats treated with T-4 (16 mu g/d ay/rat, 4 weeks) there was reverse trend in all the parameters. From t hese studies O-2(.-) and LP products appear to play a significant role in the development of goitres in hypothyroidism.