Iodine-131 uptake and turnover rate vary over short intervals in Gravesʼ disease

Background: Despite the long experience with radioiodine for hyperthyroidism, controversy remains regarding the optimal method to determine the activity that is required to achieve long-term euthyroidism. Objectives: To compare the effect of estimated versus calculated activity of radioiodine in hyperthyroidism. Design: Systematic review and meta-analysis. Methods: We searched the databases Medline, EMBASE, Web of Science, and Cochrane Library for randomized and nonrandomized studies, comparing the effect of activity estimation methods with dosimetry for hyperthyroidism. The main outcome measure was the frequency of treatment success, defined as persistent euthyroidism after radioiodine treatment at the end of follow-up in the dose estimated and calculated dosimetry group. Furthermore, we assessed the cure rates of hyperthyroidism. Results: Three randomized and five nonrandomized studies, comparing the effect of estimated versus calculated activity of radioiodine on clinical outcomes for the treatment of hyperthyroidism, were included. The weighted mean relative frequency of successful treatment outcome (euthyroidism) was 1.03 (95% confidence interval (CI) 0.91-1.16) for estimated versus calculated activity; the weighted mean relative frequency of cure of hyperthyroidism (eu-or hypothyroidism) was 1.03 (95% CI 0.96-1.10). Subgroup analysis showed a relative frequency of euthyroidism of 1.03 (95% CI 0.84-1.26) for Graves' disease and of 1.05 (95% CI 0.91-1.19) for toxic multinodular goiter. Conclusion: The two main methods used to determine the activity in the treatment of hyperthyroidism with radioiodine, estimated and calculated, resulted in an equally successful treatment outcome. However, the heterogeneity of the included studies is a strong limitation that prevents a definitive conclusion from this meta-analysis.

Section: Discussionmentioning

confidence: 99%

Clinical outcomes after estimated versus calculated activity of radioiodine for the treatment of hyperthyroidism: systematic review and meta-analysis

Rooij¹,

Vandenbroucke²,

Smit³

et al. 2009

“…This is justified by studies showing that calculated doses do not carry any advantages over fixed doses (23 -25). Detrimental to any algorithm that includes a 24-h uptake is the great variation in 131 I uptake and turnover over short periods of time (26). In addition, the correlation between the intended and the actual dose delivered to the thyroid is highly variable, with a mean coefficient of variation of 45% (27).…”

Section: Discussionmentioning

confidence: 99%

Resumption of methimazole after 131I therapy of hyperthyroid diseases: effect on thyroid function and volume evaluated by a randomized clinical trial

Bonnema

Bennedbæk

Gram³

et al. 2003

Objective: Retrospective studies have indicated that anti-thyroid drugs (ATD) might possess a radioprotective effect, leading to a higher rate of recurrence of hyperthyroidism after iodine-131 ( 131 I) therapy. Design: A randomized clinical trial was performed to clarify whether resumption of methimazole after 131 I influences the final outcome of this treatment. Methods: We assigned 149 patients with Graves' disease or a toxic nodular goitre to groups either to resume (þATD) or not to resume (2ATD) methimazole 7 days after 131 I. Before 131I therapy, all patients were rendered euthyroid by methimazole, which was discontinued 4 days before the 131 I therapy. Results: During the follow-up period of 12 months, 13 patients developed hypothyroidism, 42 were euthyroid, and 18 had recurrence of hyperthyroidism in the þATD group; the respective numbers in the 2ATD group were 16, 42 and 18 (P ¼ 0.88). At 3 weeks after 131 I therapy, the serum free-thyroxine index was slightly decreased (by 5.7%; 95% confidence interval (CI) 215.5 to 5.4%) in the þ ATD group, in contrast to an increase of 35.9% (95% CI 18.8 to 55.5%) in the 2ATD group (P , 0.001 between groups). In the subgroup that remained euthyroid during follow-up, thyroid volume reduction, assessed by ultrasonography, was smaller in the þATD group [38.7% (95% CI 33.3to 44.1%)] than in the 2ATD group [48.6% (95% CI: 41.5 -55.6%)] (P , 0.05). Conclusion:No radioprotective effect could be demonstrated, with regard to final thyroid function, for the resumpton of methimazole 7 days after 131 I therapy. Although resumption of methimazole slightly reduced the magnitude of shrinkage of the goitre obtained by 131 I, the prevention of a temporary thyrotoxicosis in the early period after radiation favours this regimen.

“…Such a relationship was suggested by the studies of Le Moli et al (82) and de Klerk et al (69), but could not be confirmed in the study of Bonnema et al (77). This inconsistency probably reflects the fact that thyroid 131 I uptake varies with time (86), and the iodine biokinetics is probably also affected by the 131 I treatment itself. The recent advent of recombinant human TSH (rhTSH), which can double the 24-h thyroid 131 I uptake, opens up new possibilities (87).…”

Section: Impact Of the Large Goitre On The Trachea And Effect Of Therapymentioning

confidence: 99%

Controversies in radioiodine therapy: relation to ophthalmopathy, the possible radioprotective effect of antithyroid drugs, and use in large goitres

Bonnema

Bartalena

Toft

et al. 2002

In routine use for more than 50 years, radioiodine ( 131 I) is generally considered safe and devoid of major side effects. Therefore, it is surprising that relatively many aspects of radioiodine therapy are controversial, as illustrated by recent international questionnaire studies. Our review aims at highlighting three of these areas -namely, the influence of 131 I on the course of Graves' ophthalmopathy, the possible radioprotective effects of antithyroid drugs, and the use of 131 I in large goitres. 131 I therapy carries a small (but definite) risk of causing progression of Graves' ophthalmopathy. Identification of risk factors (thyroid dysfunction, high level of thyroid-stimulating hormone (TSH) receptor antibodies, cigarette smoking) allows the identification of patients at risk and the institution of concomitant glucocorticoid treatment, thereby hindering progression of eye disease.On the basis, largely, of retrospective data, it appears that carbimazole (or methimazole), if stopped 3-5 days before treatment, does not influence the outcome of 131 I therapy. Simultaneous thyrostatic medication most probably reduces the efficacy of 131 I, as does restarting it within 7 days. Propylthiouracil seems to have a more prolonged radioprotective effect than carbimazole.Surgery is the treatment of first choice in patients with a large goitre. However, in the case of patient ineligibility or preference, 131 I therapy may be an option. The treatment has a favourable effect on tracheal compression and inspiratorycapacity, but the reduction in thyroid volume is only 30-40%. Inpatient treatment, necessitated by the large doses, makes the treatment cumbersome.Controversy related to radioiodine therapy is mainly based on the lack of adequate prospective randomised studies comparing efficacy, side effects, cost and patient satisfaction.