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Introduction Autoimmune reactions in Graves’ disease (GD) occur not only in the thyroid gland, but also in the orbital connective tissue, eyelids, extraocular muscles. The occurrence of orbitopathy in the course of GD is influenced by environmental factors, e.g. cigarette smoking. Objectives The aim of the study was to analyze the effect of cigarette smoking on the efficacy of activity of radioiodine(131I) therapy in patients with GD. We also studied the influence of cigarette smoking and the efficacy of prednisone prophylaxis on the risk of thyroid-associated ophthalmopathy (TAO) development after radioiodine therapy (RIT) during two years of follow-up. Patients and methods Medical records of hyperthyroid patients treated with radioiodine had been included. Patients were scheduled to visit outpatient clinics at baseline and 1, 3, 6, 9, 12, 18, and 24 months after RIT. Results The studied group consisted of 336 patients (274 women, 62 men) diagnosed with GD and treated with RIT; 130 patients received second therapeutic dose of 131I due to recurrent hyperthyroidism. Among all studied patients, 220 (65.5%) were smokers and 116 (34.5%) non-smokers. In the group of smokers 115 (52.2%) of patients received single RIT, 105 (47.8%) received second dose of RAI due to recurrent hyperthyroidism. In non-smokers 91 (78.6%) received single activity of RAI, while 25 (21.4%) patients required second RIT due to recurrent hyperthyroidism. The ophthalmic symptoms in the group of smokers after RIT were less frequent, if the patient received preventative treatment in the form of oral prednisone (P = 0.0088). Conclusions The results of our study suggest that cigarette smoking reduces the efficacy of treatment with 131I in patients with GD. The study also confirmed the effectiveness of steroid prophylaxis against TAO development or exacerbation after RIT.

The present study evaluated the effects of smoking on the amount of therapeutic doses of radioiodine ((131)I) given to patients with Graves’ disease (GB). The study also retrospectively analyzed the relationship between the onset of symptoms of thyroid ophthalmopathy (OT) after treatment with (131)I within 2 years and changes of TSHR-Abs levels, and the impact of prednisone administration before and after the therapy on OT development in both smoking and non-smoking patients.The study group included 116 patients, 97 women and 19 men, aged 28 ÷ 77 years (average 51 years) who were diagnosed with GB and treated with therapeutic doses of (131)I. Of the 116 patients treated, 85 patients were given a single dose of (131)I, whereas in 31 patients, due to recurrent hyperthyroidism, there was a need for a second dose of (131)I. In the group of 85 studied patients who received a single therapeutic dose of (131)I, 34 patients were smokers, including 27 women and 7 men, whereas in the group of 31 patients with recurrent hyperthyroidism who received repeated doses of 131I, 21 patients were smokers, 17 women and 4 men. Patients qualified for the therapy with (131)I and diagnosed with mild OT, were given prednisone, administered orally with an initial dose of 0.4 - 0.5 mg/kg daily tapering within 4-6 weeks.The results of the study demonstrated that there was a statistically significant relationship (p0.05) between cigarette smoking and the number of administered therapeutic doses of (131)I in patients with GD. Smoking patients needed to be given the second therapeutic dose of (131)I more frequently. The relationship between the onset of symptoms of OT in patients with GD and the TSHRAb in serum within two years after (131)I administration was highly significant (p0.0001). The results obtained in our study showed that efficacy of therapy was lower in smokers with GD when compared with non-smokers Since the increased titer of TSHR-Ab was associated with higher risk of OT development, especially in smokers, its routine measurement after (131)I administration could be considered in all treated patients with GD. Steroid prophylaxis should be recommended for each smoking GD patient with mild OT qualified for (131)I therapy.