Original article

Biochemical and immunological changes after antithyroid drugs, radioactive iodine, or thyroidectomy in Graves' disease: a retrospective comparative study

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Abstract

Aim: To compare changes in thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), free thyroxine (FT4), and thyrotropin receptor antibodies (TRAb) after antithyroid drugs, radioactive iodine, or total thyroidectomy in patients with Graves' disease.

Methods: This retrospective comparative cohort study included 60 adults treated at the University Clinical Centre Tuzla between 2021 and 2025, with 20 patients in each treatment group. Laboratory values obtained before treatment and at the first documented follow-up were analysed. The primary analysis compared change scores among treatment groups; within-group changes and correlations were secondary analyses.

Results: Baseline FT4 and TRAb differed among the treatment groups (p = 0.022 and p = 0.005, respectively). After thyroidectomy, FT3 and TRAb changed significantly (p = 0.004 and p < 0.001), whereas TSH and FT3 changed significantly within the radioactive iodine group (p = 0.014 and p = 0.027). No significant within-group changes were observed after antithyroid drug treatment. Change scores did not differ significantly among the groups for TSH, FT3, FT4, or TRAb. Changes in FT3 and FT4 were positively correlated (ρ = 0.649; p < 0.001), whereas changes in TSH were negatively correlated with FT3 and FT4.

Conclusion: Selected laboratory parameters changed within the thyroidectomy and radioactive iodine groups, but change scores did not differ significantly among the three treatment groups. These comparisons should be interpreted in view of baseline imbalance, small group sizes, non-consecutive sampling, and non-standardised follow-up.

Keywords: antithyroid agents, Graves’ disease, iodine radioisotopes, thyroidectomy, treatment outcome