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ACUTE EFFECT OF INORGANIC IODIDE AFTER 131 I THERAPY FOR HYPERTHYROIDISM
Author(s) -
SCHIMMEL MARTIN,
UTIGER ROBERT D.
Publication year - 1977
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1111/j.1365-2265.1977.tb02018.x
Subject(s) - iodide , medicine , endocrinology , triiodothyronine , iodine , thyroid , chemistry , organic chemistry
SUMMARY Patients treated with inorganic iodide weeks to years following 131 I therapy for hyperthyroidism do not adapt to its antithyroid effect. To determine whether such adaptation occurs soon after 131 I therapy, serum thyroxine (T4) and triiodothyronine (T3) concentrations were measured daily for 9‐14 days following 131 I therapy in seventeen hyperthyroid patients. Nine patients received 150 mg KI daily starting 48 h after 131 I administration; eight received only 131 I. Serum T4 and T3 concentrations did not change significantly in the patients who received only 131 I. In the patients who received 131 I and KI, serum T4 and T3 concentrations fell promptly, reaching nadir values 2‐10 days after initiation of iodide, and then increased despite continuation of KI therapy. The mean maximal fall in serum T4 was 34% and in serum T3 42%. These results show that ‘escape’ from the acute antithyroid effect of iodide occurs when it is given immediately after 131 I therapy, thus limiting the utility of iodide as a therapeutic agent at this time. 131 I‐iodide is a widely used and effective form of therapy for hyperthyroidism. Reduction in thyroid hormone does not occur within the first weeks after 131 I therapy. Exacerbation of hyperthyroidism may occur shortly after 131 I administration, with frequency ranging from 0 to 11% in several large species (Chapman et al ., 1954; Cassidy & Astwood, 1959; Lamberg et al ., 1959; Green & Wilson, 1964). Such exacerbations are thought to reflect acute thyroid radiation necrosis and subsequent hormone release, and may limit the use of 131 I therapeutically. Inorganic iodide is a rapidly, but usually transiently, effective antithyroid agent when used alone. No reports are available concerning the efficacy of iodide when given immediately following 131 I therapy. Since some hormone release after 131 I therapy may reflect thyroid destruction, rather than secretion, it is possible iodide might be less effective in this setting. On the other hand, if iodine is effective immediately after 131 I therapy, especially if its action is sustained (as occurs in patients treated with 131 I months or years previously; Hagen et al ., 1967; Braverman et al ., 1969), it might be a useful adjunct for certain hyperthyroid patients treated with 131 I. This report describes the result of a study of patients so treated.