IngentaConnect Outcome of radioiodine-131 therapy in hyperfunctioning thyroid no...

Abstract:

Summary Objective

To investigate the risk of hypothyroidism after radioiodine (¹³¹I) treatment for hyperfunctioning thyroid nodules. Design

Retrospective analysis of patients treated with ¹³¹I for hyperfunctioning thyroid nodules and followed up for a maximum of 20 years. Patients

A total of 346 patients treated with ¹³¹I in the years 1975–95, for a single hyperfunctioning nodule. Measurements

Hypothyroidism was defined as TSH levels > 3·7 mU/l. Kaplan–Meier survival analysis was used to analyse permanence of euthyroidism after ¹³¹I. A stepwise Cox proportional hazard model was used to identify factors influencing the progression to hypothyroidism. Results

The cumulative incidence of hypothyroidism was 7·6% at 1 year, 28% at 5 years, 46% at 10 years and 60% at 20 years. Age (P < 0·01), 24-th ¹³¹I uptake (P < 0·05) and previous treatment with methimazole (MMI, P < 0·1) were associated with a faster progression towards hypothyroidism, while thyroid and nodule size, thyroid status at diagnosis and degree of extranodular thyroid parenchymal suppression had no influence. In hyperthyroid patients with partial parenchymal suppression, however, previous MMI treatment was the most important prognostic factor (P < 0·01). Conclusions

After 20 years of follow-up, 60% of patients treated with ¹³¹I for a single hyperfunctioning nodule are hypothyroid. Factors increasing the risk of hypothyroidism are age, ¹³¹I uptake and MMI pretreatment. The prognostic value of this last factor, however, depends on the degree of suppression of the extranodular thyroid parenchyma at the scan.

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Outcome of radioiodine-131 therapy in hyperfunctioning thyroid nodules: a 20 years’ retrospective study