The influence of thiamazole, lithium carbonate, or prednisone administration on the efficacy of radioiodine treatment ( 131 I) in hyperthyroid patients

Abstract

Introduction: The effects of selected drugs (see below) on the efficacy of (¹³¹I) radioiodine therapy were examined.
Material and methods: The study involved 200 hyperthyroid patients, treated with radioactive iodine. They were divided into five groups (40 persons in each). In Group I - patients were administered ¹³¹I and thiamazole; in Group II they were given - ¹³¹I and lithium carbonate; in Group III they were given - ¹³¹I only (the assumed absorbed dose - 150-200 Gy, the same as in Groups I and II, for which Group III was a control group); in Group IV they were given - ¹³¹I and prednisone; and in Group V they were given - ¹³¹I only (250-350 Gy, the same as in Group IV, for which Group V was a control group). Therapeutic results were analyzed after six months based on clinical and hormonal status. The evaluation also included effects of the initial hormonal status on the outcome of ¹³¹I therapy in Groups II and IV (v. respective controls, i.e. Groups III and V); such analysis was not performed in Group I because all the patients in that group were initially hyperthyroid.
Results: In 145 patients (72.5%) the therapy with ¹³¹I was effective. In 55 patients (27.5%) the therapy was ineffective. The application of thiamazole during the peritherapeutic period in patients treated with 131I reduced the effectiveness of radioiodine, while lithium carbonate had no effect on the therapy outcome. Prednisone increased the effectiveness of the therapy with ¹³¹I. Normalisation of the initial concentration of TSH was advantageous for the ¹³¹I therapeutic outcome only when the assumed absorbed doses of 150–200 Gy were applied, while being of no avail for doses above 250 Gy.
Conclusions: The present results indicate the necessity of careful analysis of administered drugs in hyperthyroid patients while qualifying them to ¹³¹I therapy. The initial concentration of TSH has no effect on the efficacy of radioiodine therapy in cases where absorbed doses are regarded to be ablative.
(Pol J Endocrinol 2010; 61 (1): 56-61)