Endocrine Abstracts

Introduction: In treating hyperthyroidism in Graves’ disease (GD) patients with 131-iodine, the optimum activity of radioiodide is yet to be established. We analysed factors affecting the efficacy of ¹³¹I radiotherapy in GD patients.

Materials and methods: The analysed group consisted of 362 (80.9% females and 19.1% males) GD patients, of median age 53 (min: 14 and max: 85) years. GD was diagnosed from clinical features, laboratory tests, thyroid USG, and scintigraphy. All patients with orbitopathy (GO) received glucocorticoids to prevent GO exacerbation. Focal lesions were observed in 164 (84% females and 16% males) patients. ¹³¹I was applied for the first time in 85.4% of patients; 45.8% received ¹³¹I more than once; 6.1% of all patients received it on first onset of hyperthyroidism, while 48.1% received it on first recurrence. The activity delivered was based on clinical status, thyroid USG-established volume and 24-h ¹³¹I uptake. Ranges of ¹³¹I activity applied were: up to 555, 555–800, and above 800 MBq. Six months post ¹³¹I treatment euthyroidism or hypothyroidism were stated in 72% of patients.

Results: The median thyroid volume was significantly larger in men (30 ml (18.95–52.75)) than in women (24 ml (16.1–37)) (P=0.006). No significant differences in efficacy related to ¹³¹I activity applied were stated six months post treatment. In the group of patients treated with lower (<555 MBq) or higher (555–800 MBq) ¹³¹I activity, 76 or 68.5% of patients, respectively, were effectively cured. Presence of focal lesions did not affect the efficacy of ¹³¹I treatment either. In the group of 28 GO patients significant increase of hTRAB level was observed. De novo GO occurred in 1.9% of patients.

Conclusions: The efficacy of ¹³¹I treatment in GD patients evaluated after 6 months was negatively affected by larger thyroid volumes and by anti-thyroid medication.