Oxidative stress plays an important role in hyperthyroidism induced tissue damage.
We aimed to determine whether radioiodine therapy (RIT) has benefit effect on the oxidant and antioxidant status in subclinical hyperthyroidism.
Material and methods: We studied 40 patients with untreated subclinical hyperthyroidism, (33 female, 7 male), aged 2378 years; 14 patients with multinodular goitre, and 25 patients with solitary autonomous nodule. Twelve normal adult volunteers as control group.
Before the treatment all the patients has normal levels of serum fT3, fT4, low levels of serum TSH (<0.1 mU/l) and effective half-life was more than 3 days. Malignant changes were excluded in all nodules by fine needle aspiration biopsy.
In the investigated groups, we evaluate malondialdehyde (MDA) as a marker of oxidative stress, glutathione (GSH) and glutathione peroxidase (GPx) activity as a parameters of antioxidant system before and 6 months after RIT.
The serum fT4, fT3 and TSH were evaluated before and monthly up to 12 months after RIT. Thyroid ultrasound, and thyroid scan were done before and after12 months of 131I therapy. The activity dose was calculated by Marinellis formula and ranged between 200 and 600 MBq. The absorbed dose ranged between 160 and 280 Gy.
Results: Subclinical hyperthyroidism caused a significant increase in MDA level (P<0.05) as well as a significant decrease in GPx activities (P<0.05) and GSH level (P<0.05) compared to euthyroid controls subject.
Achievement of euthyroidism after 6 months of radioiodine administration resulted in a significant decrease of MDA, significant increase of GSH and non significant increase in GPx activities. Thyroid volume reduced to 45% (average); 38 patient were in euthyroidism, two patients received 2 doses of RIT.
Conclusions: Our results confirm the imbalance of the antioxidant/oxidant status in subclinical hyperthyroidism. RIT was more effective to improve these balances.