Time to Normalization and Sustainable Normal Serum Thyrotropin Concentrations in Patients with Hyperthyroidism: Comparison of Methimazole and Radioactive Iodine Treatments

Elsevier

Available online 7 August 2022

Endocrine PracticeAbstractObjective

The aim of this study was to compare the “time to euthyroidism” and “time spent in euthyroidism” following methimazole (MMI) and radioactive iodine (RAI) treatments.

Methods

Three hundred fifty-eight patients with hyperthyroidism, 178 who underwent long-term MMI treatment and 180 patients who underwent RAI treatment, were analyzed. The time to normalization of increased serum values of free thyroxine and triiodothyronine and suppressed serum thyroid-stimulating hormone (TSH) values as well as the percentage of time that the thyroid hormone levels remained within normal ranges during a mean follow-up time of 12 years were compared.

Results

The mean time to euthyroidism was 4.59 ± 2.63 months (range, 2-16 months) in the MMI group and 15.39 ± 12.11 months (range, 2-61 months) in the RAI group (P < .001). During follow-up, the percentage of time spent in euthyroidism was 94.5% ± 7.3% and 82.5% + 11.0% in the MMI and RAI groups, respectively (P < .001). Serum TSH values above and below the normal range were observed in 5.3% and 0.2% of patients, respectively, in the MMI group and 9.8% and 7.7% of patients, respectively, in the RAI group (P < .001). The time to euthyroidism and the percentage of time spent in euthyroidism in 40 RAI-treated patients with euthyroidism were similar to those in the MMI group and significantly shorter than those in the RAI-treated hypothyroid and relapsed subgroups. In patients who continued MMI therapy for >10 years, the percentage of time spent in euthyroidism was >99%.

Conclusion

In our cohort of selected patients, MMI therapy was accompanied by faster achievement of the euthyroid state and more sustained normal serum TSH levels during long-term follow-up compared with RAI therapy.

AbbreviationsLT-ATD

long-term antithyroid drug

LT-MMI

long-term methimazole

RAI-Eu

radioactive iodine-treated patients who became euthyroid

RAI-Hypo

radioactive iodine-treated patients who had overt hypothyroidism

RAI-Relapse

radioactive iodine-treated patients who experienced relapse

TOHID

Towards Outstanding Hyperthyroid Care Induced by Antithyroid Drugs

TSH

thyroid-stimulating hormone

Key words

hyperthyroidism

Graves' disease

antithyroid drugs

methimazole

long-term

radioactive iodine

euthyroidism

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© 2022 AACE. Published by Elsevier Inc. All rights reserved.

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