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Radioiodine-131 treatment of thyrotoxicosis: dose required for and some factors affecting the early induction of hypothyroidism

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The results of sodium iodide 131I treatment of thyrotoxicosis in 1,168 patients (302 males, 866 females; 58.5% diffuse and 41.5% multinodular toxic goitre) are presented. At the end of the 1st year post-treatment, 54.4% were hypothyroid, and the incidence of hypothyroidism after the 2nd year increased by 3% per year. When the results were analysed according to the calculated radiation dose the thyroid, it was found that the cumulative incidence of hypothyroidism from 6 months to 2 years posttreatment rose almost proportionally to the dose in cases of doses of 1,500–15,000 rad, but increased very little for higher doses; however, the long-term incidence of hypothyroidism was almost independent of the thyroid dose. Multivariate analysis showed that the results of 131I therapy at 6 months depended also on sex (treatment being more effective in women), the consistency of the thyroid gland and the year of treatment, with the same radiation dose giving a higher incidence of hypothyroidism in patients treated recently, in comparison to those treated early in the period studied. Of the patients treated in the period 1978–1982 (mean dose, 300 μCi/g), 93.5% were cured with a single dose of 131I, and 78% were hypothyroid at 6 months post-treatment.

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Correspondence to C. C. Alevizaki.

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Alevizaki, C.C., Alevizaki-Harhalaki, M.C. & Ikkos, D.G. Radioiodine-131 treatment of thyrotoxicosis: dose required for and some factors affecting the early induction of hypothyroidism. Eur J Nucl Med 10, 450–454 (1985). https://doi.org/10.1007/BF00256589

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Key words

  • Thyrotoxicosis
  • iodine 131 therapy