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Title: Radioiodine therapy efficacy in patients with Graves’ disease: factors influencing the effectiveness of the treatment


Radioiodine therapy is commonly considered to be safe and efficacious treatment option for hyperthyroidism in the course of Graves’ disease. Despite the fact that radioiodine treatment has been used since 1940s, an explicit algorithm regarding radioiodine activity selection has not yet been established. There are two methods of radioiodine activity selection currently used in the clinical practice: one is calculated doses regimen based on formula taking into account glandular volume and estimated radioiodine uptakewhile the other one relies on the use of fixed doses.The aim of this study was to assess radioiodine therapy efficacy in patients with Graves' disease and to analyze factors that influence the effectiveness of the treatment.362 patients with Graves' disease (80,9% female, 19,1% male) treated in the years 2006-2010 in the Nuclear Medicine Center, Division of Clinical Endocrinology Ward at the Jagiellonian University in Cracow were enrolled in the study. Hyperthyroidism in the course of Graves’ disease was diagnosed based on clinical picture, pathology results, thyroid ultrasound and thyroid scintigraphy results. Age median of the studied group of the patients was 53 years (min 14 to 85 max). Thyroid volume in men (30 mls [18.95-52,75]) proved to be statistically bigger than in women (24 ml [16.1- 37]) (p=0,006). Thyroid nodules were found in 164 patients (84% women and ; 16% men).In the studied group 85,4% of patients received radioiodine for the first time, 6,1% of the patients had first episode of hyperthyroidism treated with radioiodine, 48,1% of the patients received radioiodine due to the first recurrence of the disease, 45,8% of the patients were given radioiodine for the second or the following recurrence of the disease. Patients received radioiodine activities ranged in three activity brackets: up to 555 MBq 131-I, 555-800 MBq 131-I and above 800 MBq 131-I. Clinical status of the patient, intended treatment goals, US assessed thyroid volume and thyroid iodine uptake were all taken into account during radioiodine activity adjustment. 131-I treatment efficacy was analyzed in the following patients’ subgroups in relation to sex, presence or absence of thyroid nodules, 131-I activity used and in patients with Graves’ orbitopathy (GO). 72% of the patients remained permanently euthyroid or hypothyroid requiring L-thyroxine supplementation 6 months after 131-I administration which was defined as successful treatment in the studied group of the patients. 73% of the women and 66,7% of the men achieved desired therapeutic goal, while subgroups analysis in relation to applied 131-I activity revealed that 76% of the patients who received lowest 131-I activity (<555 MBq) and 68,5% of those who received medium 131-I activity (555-800 MBq) were consi ; dered to be successfully treated. There was no statistical difference in treatment efficacy noted between 3 subgroups receiving small, medium and high 131-I activities when assessed 6 months after 131-I treatment completion. Statistically significant difference of 131-I activity was found in two groups: with and without thyroid nodules (575 MBq vs 555 MBq)(p=0,001). Comparison of treatment efficacy assessed 6 months following 131-I administration in relation to the presence or absence of the thyroid nodules did not prove to be statistically different. ; In the group of 28 patients with mild GO (CAS<3 points, NOSPECS <4 points) treated with 131-I along with glucocorticosteroid cover 75% of them met criteria of successful treatment after 6 months. Correlation of serum hTRAb concentration before and 6 weeks after 131-I treatment proved to be weak (Rs=0.30, p=0,041). Elevation of serum hTRAb concentration measured 6 weeks after 131-I treatmentin comparison to serum hTRAb concentration before treatment was statistically significant and substantially higher in the group of patients in which 131-I treatment was considered to be successful after six months compared to the group of patients in which treatment failed. There were 7 patients (1,9%) out of 362 in the study with new GO, whereas progression of preexisting GO was noted in 2 patients (0,6%). All the patients with preexisting GO ; received glucocorticosteroid cover.Conclusions: The study showed that 131-I treatment efficacy assessed 6 months after radioiodine administration in the group of patients with Graves’ disease was only influenced by thyroid volume – the smaller the volume, the more efficacious radioiodine treatment was, and this correlation proved to be statistically significant. In the subgroup of the patients with Graves’ disease and thyroid nodules thyroid volume was also a statistically significant factor contributing to positive outcome of radioiodine treatment after six months, while it was demonstrated that use of antithyroid drugs prior to 131-I treatment reduced cure rate by 30% in this subgroup of the patients.

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2 - studia doktoranckie

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Wydział Lekarski


Pach, Dorota

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Mar 16, 2023

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Nov 9, 2015

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Edition name Date
ZB-123154 Mar 16, 2023


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