Long-term Effects of Radioiodine in Toxic Multinodular Goiter: Thyroid Volume, Function, and Autoimmunity

Abstract

Context Long-term studies evaluating the treatment of toxic multinodular goiter (TMNG) with fixed activities of radioiodine (RAI) are lacking. Objective The objective of this work is to describe the effects of 15 mCi on thyroid volume, function, and autoimmunity in the long term. Design and Setting A population-based, retrospective analysis with up to 12 years of follow-up was conducted in Siena, Italy. Participants Adult patients (n = 153) with TMNG, naive to RAI, were included. Methods Evaluation was performed of thyroid function, antithyroid antibodies, and ultrasound scans before and yearly after RAI. Main Outcome Measures Evaluations included hyperthyroidism cure, hypothyroidism, volume reduction, nadir and regain, and antibody titer change. Results The study revealed mean volume reductions greater than or equal to 50% at 3 years after RAI; the greatest annual reduction was observed during the first year (30 ± 17.8%; P < .001). Most patients (60%) achieved their volume nadir 3 to 6 years after RAI. Although 22% patients showed volume regain, the net reduction was statistically significant as late as 9 years after RAI (P = .005). The mean time to hypothyroidism was 2.7 ± 2.4 years, and it was associated with greater reductions in volume (P = .01). During the first 3 years after treatment, hyperthyroid patients decreased approximately by 50% per year without additional RAI. There was no statistically significant association of antibody titers with thyroid function except for antithyrotropin receptor antibodies and hyperthyroidism (P = .004). At the end of follow-up there were 61.6% euthyroid patients, 11% hyperthyroid (4.8% overt), and 27.4% hypothyroid patients (2.7% overt). Hyperthyroidism was cured in 89%. Conclusions The treatment of TMNG with 15 mCi of RAI induced low hypothyroidism rates while providing high cure rates and significant volume reduction, which was maintained in the long term.

Long-Term Follow-up of Patients With Autonomous Thyroid Nodules Treated With Radioiodine

“…Other studies have also shown that the presence of antithyroid antibodies and unsuppressed TSH at the time of 131 I treatment increases the chance of progression to hypothyroidism. 7,10,20 In the present study, antithyroid antibodies were positive in only 9 of 96 patients (9.4%), but their presence did not influence the therapeutic response, as also described by Roque et al 18 In the group of responder patients who remained in euthyroidism up to 12 months after 131 I, a small portion had a recurrence of hyperthyroidism (6.1%), and 16% evolved with hypothyroidism, highlighting the importance of clinical and laboratory follow-up. Indeed, previous studies 7,16 showed that the late cumulative rate of hypothyroidism after a single 131 I dose increases progressively, reaching almost 50% (72/147 cases) after up to 20 years of follow-up.…”

“…Regarding the change in thyroid volume after 131 I treatment, more than half showed a volume decrease greater than 40%, a result similar to that obtained in other studies. 2,18,21,22 It is noteworthy that 131 I treatment was well tolerated, with an adverse effect occurring around 2.4%, slightly higher than that described by other authors. 7 The major limitation of the present study is that it is retrospective.…”

“…17 Thus, most patients in this study were initially diagnosed with subclinical hyperthyroidism (68%), which is consistent with the literature. 12,18 Also, most individuals presented with MNG, whereas in the literature, this percentage varies between 30% and 86%. 2,7,11,13,15,16 In the present study, patients received a higher activity of 131 I than that described in the literature, which ranged from 4 to 50 mCi.…”

“…2,7,11,14,17 As expected, patients with autonomous nodules were older, with a mean age of 60 years, which agrees with other studies. 7,8,18 Typically, thyrotoxicosis due to autonomous nodules evolves gradually because most hormone overproduction depends on nodule growth, and the finding of subclinical hyperthyroidism is quite common. 17 Thus, most patients in this study were initially diagnosed with subclinical hyperthyroidism (68%), which is consistent with the literature.…”

Il gozzo multinodulare

“…I gozzi molto grandi con associati sintomi compressivi o con noduli maligni sono indirizzati all'intervento chirurgico. Il trattamento radiometabolico con 131 I rappresenta, invece, un'opzione terapeutica molto valida in caso di adenomi tossici o di gozzi multinodulari tossici [19]. Lo iodio radioattivo si concentra, infatti, quasi esclusivamente nei noduli con autonomia funzionale, determinandone la distruzione con risoluzione dell'ipertiroidismo e notevole riduzione dimensionale.…”