Radioiodine therapy activity 550 MBq of I131 in thyrotoxicosis patients

Background. Radioiodine therapy (RIT) is an alternative method to surgical treatment used in the treatment of hyperthyroidism (Graves’ disease or solitary/multinodular toxic goiter (STG/MTG) etiology). However, treatment protocol doesn’t exist.

Aim. To evaluate the outcomes of the I131 treatment in hyperthyroidism using the standard dose (550 Mbq), and to explore the factors that influence the outcome of treatment.

Methods. We studied 38 patients (35 women and 3 men) with hyperthyroidism. Each patient was carried I131 RIT in a dose of 550 Mbq. Patients were randomized 2 group – patients with Graves' disease and patients with a solitary/multinodular toxic goiter. Antithyroid drugs withdraw was usually conducted for 7–14 days prior to RIT. Follow-up period ranged from 6 to 8 months, the average was 6.6 ± 0.4 months.

Results. Six months after the RIT 23 patients (61%) reached hypothyroidism, 7 patients (18%) was observed euthyroidism, thyrotoxicosis stayed in 8 patients (21%). In patients with Graves&apos; disease onset hypothyroidism were more likely (75% vs 35.7%, p < 0.001). Thus at STG/MTG achieve euthyrosis percentage was higher (28.6% vs 12.5%). Predictors of a positive outcome of the treatment are: less thyroid size (<30 ml for women, <40 ml for men) and younger age (under 35 years old). Statistical significance in influencing the outcome of treatment by disease duration, level of stimulating antibodies against thyrotropin receptors have not been identified.

Conclusions. Fixed activity of 550 MBq I131 has a different efficacy in the treatment of hyperthyroidism in patients with Graves’ disease and STG/MTG. In addition, on treatment results affect patient age and the size of the thyroid gland, which should be considered during planning RIT. In order to improve the effectiveness of radioiodine therapy of hyperthyroidism requires personalization tactics of treatment based on clinical factors, as well as the use of in vivo dosimetry planning when therapeutic activity calculating.

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