Thyroid dysfunction after radioiodine therapy common with Graves’ disease
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Among adults with Graves’ disease, thyroid dysfunction was common and often recurrent during the first 12 months after radioiodine treatment, according to findings from the PRAGMA study.
For the retrospective, multicenter, observational study, Petros Perros, BSc, MBBS, MD, a consultant endocrinologist at the Royal Victoria Infirmary in Newcastle upon Tyne, United Kingdom, and colleagues aimed to quantify the frequency of abnormal thyroid function after radioiodine and compare the efficacy of common management approaches for Graves’ disease. They included adult patients treated with radioiodine who had 12 months of follow‐up after therapy and whose most recent radioiodine dose was administered at least 1 year before enrollment.
The researchers defined euthyroidism as both serum thyroid-stimulating hormone and free thyroxine within their reference ranges or, when only one was available, within its reference range; hypothyroidism as TSH at least 10 mU/L or subnormal free T4 regardless of TSH; hyperthyroidism as TSH below and free T4 above their reference ranges; dysthyroidism as the sum of hypo‐ and hyperthyroidism; subclinical hypothyroidism as normal free T4 and TSH between the upper limit of normal and less than 10 mU/L; and subclinical hyperthyroidism as low TSH and normal free T4.
Overall, the study involved 812 patients from 31 U.K. centers who were studied after radioiodine therapy, of whom hypothyroidism occurred in 80.7% and hyperthyroidism in 48.6%.
Of the three principal management strategies employed after radioiodine therapy — antithyroid drugs alone, levothyroxine alone and a combination of the two — differences between them were small. Researchers found that adherence to national guidelines concerning thyroid function monitoring in the first 6 months was low, between 21.4% and 28.7%.
In addition, dysthyroidism was not associated with any negative outcomes, including new‐onset or exacerbation of Graves’ orbitopathy, weight gain and cardiovascular events, and no significant differences between centers were observed in demographics, clinical practice and thyroid status after radioiodine.
“Dysthyroidism in the first 12 months after radioiodine, especially hypothyroidism, is very common and often recurrent, suggesting suboptimal management,” the researchers concluded. “The findings of PRAGMA indicate that guidance from professional organizations on whether avoidance of dysthyroidism after radioiodine should be pursued rigorously by clinicians for all patients with Graves’ disease post‐radioiodine would be valuable.”
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