Radioactive Iodine for the Treatment of Subclinical Thyrotoxicosis Grade 1 and 2: Outcome of up to 18-Year Follow Up

Abstract

BackgroundSubclinical thyrotoxicosis (SCT) is associated with significant morbidity and mortality, specifically increased risk of atrial fibrillation and cardiovascular death. The management is ill-defined due to the scarcity of randomised controlled studies. Some clinicians recommend radioiodine (RAI) treatment however its long-term outcome is unknown. Therefore, further data is needed to provide robust evidence-based guidelines.MethodsA prospective, single-protocol analysis of the outcome of SCT patients (Grade 1; 0.1-0.4 mIU/L and Grade 2; <0.1 mIU/L) treated with mean dose of 427 MBq of I131, followed up for up to 18 years. Thyroid function tests were measured at 4-6 weeks, 3-, 6-, and 12-months post-RAI, and annually thereafter. Cure was defined as achieving a euthyroid/hypothyroid state.ResultsSeventy-eight patients with a median age of 68 years (range 36-84) and varying aetiology [55 toxic multinodular goitre (TMNG), 10 toxic nodule (TN) and 13 Graves’ disease (GD)] were followed up for a median period of 7.5 years (range 1-18). The cure rate was 100%. The rates of hypothyroidism in TMNG, TN and GD were 23.6%, 30% and 38.5% respectively. The median time to hypothyroidism was 6 and 12 months in GD and TMNG/TN respectively. No differences in outcome between Grade 1 versus Grade 2 were observed.ConclusionRAI using single mean dose of 427 MBq is effective and safe, irrespective of aetiology or grade of TSH suppression. GD patients become hypothyroid within the first year, whilst TMNG/TN for up to 9-years. Thus after 12 months of follow up, annual thyroid function monitoring is advised.

Subclinical Thyrotoxicosis and Cardiovascular Risk: Assessment of Circulating Endothelial Progenitor Cells, Proangiogenic Cells, and Endothelial Function

“…We have just reported that treatment of SCT can lead to a 100% cure using radioiodine therapy ( 41 ). However, there are no randomized clinical studies to guide us on the ideal management of SCT or the reduction of cardiovascular risk.…”

“…Measuring TSH levels routinely every 6 months should be considered in all adults with untreated SCT, with further evaluation of FT4 and FT3 if the TSH level is not within the reference range ( 42 ). A brief summary of the guidelines for the management of SCT has been published in our previous paper ( 41 ). The Medical Research Council-funded pilot study in the United Kingdom showed difficulty with the recruitment of patients with SCT into intervention with radioiodine therapy.…”

Effect of Radioiodine Treatment on Quality of Life in Patients with Subclinical Hyperthyroidism: A Prospective Controlled Study

“…Recent studies extended the cardiovascular risk profile to the presence of subclinical hyperthyroidism or even a formally "normal" thyroid function with higher FT4 levels within the normal range [5,6,7,8]. Consequently, RIT has been more frequently considered in patients with borderline conditions and subclinical hyperthyroidism, not only overt symptomatic hyperthyroidism [9]. In these patients, RIT is mainly supposed to contribute to cardiac risk reduction rather than alleviating thyroid specific symptoms.…”