Effect of multiple factors on success rate of high dose radioiodine therapy (>۱۵۰µCi/gr) in ۱۶۴ patients with hyperthyroidism [Persian]

Background: Radiodine therapy (RIT) for hyperthyroidism is increasingly used as a therapy of choice in most of the patients. Effect of multiple factors on the result of therapy was noted. This study tries to analyze the effect of multiple factors on success rate of RIT. Methods and patients: One hundred and sixty four hyperthyroid patients referred for RIT therapy from ۱۹۹۶-۹۹, were studied. Thyroid examination and ۲۴ hrs RAIU were performed in all patients and ۱۵۰-۲۵۵ μCi/gr of ¹³¹I was administered. Follow up of the patients, including thyroid examination and thyroid values measurements were done at ۲-۶ months after treatment. The patients were divided in two groups: those who responded to radioiodine (group ۱) and those who did not (group ۲). Results: Two to six months after RIT, seventy one percent of the patients were in group ۱ and ۲۹% in group ۲. No difference was noted in the mean age [۴۵.۷ yrs vs ۴۷.۲ yrs] (P=۰.۴۲), total Iodine dose [۱۵.۴ mCi vs ۱۷.۲] (P=۰.۲), Iodine dose per gram of thyroid weight [۱۸۹.۳ μCi/gr vs ۱۹۲.۶ μCi/gr] (P=۰.۰۶) and female/male ratio [۶۵/۲۱ vs ۳۰/۵] (P=۰.۳۲) between two groups. The mean thyroid weight was ۵۹.۱ gr in group ۱ and ۵۵.۲ gr in group ۲. Using logistic regression, the only significant effective factor in success of therapy was thyroid weight (R=۰.۱۷۲, P=۰.۰۳). With inceasing thyroid weight, success rate of Iodine therapy was decreased. Conclusion: With high dose (>۱۵۰ μCi/gr) RIT, only thyroid weight negatively affects the result of the therapy and the other factors have no significant role.