Introduction: 131-I treatment of nodular, especially nontoxic, goitre is still reserved mainly for elderly patients, whose numerous concomitant diseases disqualify them from surgery. Therapy often involves isolation and is available only in selected centres, which may be located far from some patients’ places of residence, which is inconvenient for elderly people. The aim of the study was to assess the effectiveness of outpatient fractionated 131-I treatment of patients with large nodular goitres, as well as to evaluate complications and the factors affecting treatment results.

Material and methods: The study included 35 patients with a large nodular goitre. Thyroid volume and treatment results were evaluated using US and CT neck examination.

Results: Mean thyroid volume prior to treatment was 104.36 mL (range 36.23–301.09 mL). An average administered 131-I activity was 1806 MBq (range 800–4000). The average reduction of goitre volume was 43.18% (range –17.23–89.66%). Final treatment results correlated with the thyroid size reduction obtained three months after treatment (r = 0.74; p = 0.001). Symptoms of transient hyperthyroidism were observed in 8.57% of patients, in 5.4% Graves disease was induced (including severe Graves’ orbitopathy in 2.7%), and in 2.86% TRAb increase without development of hyperthyroidism was observed. The treatment results were not influenced by initial thyroid volume (r = –0.01; p = 0.95). An increase in thyroid volume during the treatment was reported in 20% of patients, with a mean increase of 22.3% (range 0.63–55.03%). Post-treatment hypothyroidism was diagnosed in 42.9% of patients. One patient was diagnosed with salivary gland damage.

Conclusions: Fractionated 131-I treatment of large nodular goitres is an effective method, the results of which are comparable to those obtained from the administration of one-time high doses of radioiodine. (Endokrynol Pol 2015; 66 (4): 301–307)