Radioiodine Therapy In Graves Research Articles

Clinical and immunological predictors of Graves' orbitopathy after radioiodine therapy of Graves' disease

Data on the effect of 131I on the course of Graves' orbitopathy (GO) are contradictory. A number of studies indicate a deterioration in the course of GO against the background of RAIT, in other studies such a connection has not been established. Cytokines that regulate inflammation could potentially be biomarkers for assessing GO activity and predicting the course of GO after RAIT. The purpose of this study was to evaluate the dynamics of eye symptoms and analyze immunological parameters: cytokine TGF-β1 and cytokine receptors: sTNFα-R1, sTNFα-R2, sIL-2R, sIL-6R over time after RAIT, as possible predictors of GO activation. The study included 59 patients (118 orbits) with GD in the state of euthyroidism and subclinical hyperthyroidism and low active and inactive GO, aimed at conducting RAIT. Concentrations of cytokine TGF-β1, sTNFα-RI and sTNFα-R2, sIL-2R, sIL-6R, TSH receptor antibodies (rTSH-Ab), free thyroxine (FT4) and free triiodothyronine (FT3), -thyroid-stimulating hormone (TSH) in the blood serum were determined. Ultrasound examination of the thyroid gland, multispiral computed tomography (MSCT)/magnetic resonance imaging (MRI) of the orbits was performed. The examination was carried out 3, 6, 12 months after the RAIT. The deterioration of the course of the GO (1-2 points according to CAS) was noted after 3 months. (32.5%) and to a lesser degree after 6 and 12 months (13.2% and 8.45%, respectively). Dynamics were not noted, approximately, in the same number of patients (40.5%, 41.5%, 45.8%, respectively). An improvement in the course of the GO was noted after 6 and 12 months (45.3, 45.8, respectively). After 3 and 6 months, the achievement of hypothyroidism and a significant increase in the level of rTSH-Ab were noted. In the analysis of cytokines and their receptors a significant decrease in the level of TGF-β1 was noted after 3, 6 and 12 months. There was also a significant decrease in sTNF-R1 and sIL-2R at 3 and 6 months. The level of sTNFα-R2 significantly decreased 3 months after RAIT. The level of sIL-6R has not changed significantly. After 3 months in patients with positive dynamics of image intensification, the level of TGF-β1 did not significantly change compared with the level before RAIT, in patients with worsening of the course of GO or without dynamics, the level of TGF-β1 significantly decreased. After 6 months, there was the same trend, not reaching statistical significance. The IgG4 level and the IgG4/IgG ratio increased to 6 and 12 months, which corresponded to an increase in diplopia index. The main limiting factor in the conduct of RAIT is the activity of the autoimmune process in the orbits. Since patients with inactive (CAS 0-2) or low activity (CAS 3-4) GO were referred for RAIT, there was no pronounced activation of GO after RAIT. There was a slight deterioration in the course of GO by only 1-2 points according to CAS after 3 months. (32.5%) and to a lesser degree after 6 months (13.2%). In the study, it was found that the main predictors of the deterioration of the course of GO after RAIT are uncompensated hypothyroidism, a high level of rTSH-Ab and a decrease in the level of cytokine TGF-β1.

Euthyroidism: following a course of radio iodine therapy for Graves' disease

Euthyroidism: following a course of radio iodine therapy for Graves' disease

Decrease the functional activity of adaptive immunity cells one month after radioiodine therapy for Graves' diseaseDecrease the functional activity of adaptive immunity cells one month after radioiodine therapy for Graves' disease

Decrease the functional activity of adaptive immunity cells one month after radioiodine therapy for Graves' diseaseDecrease the functional activity of adaptive immunity cells one month after radioiodine therapy for Graves' disease

Influence of high tissue-absorbed dose on anti-thyroid antibodies in radioiodine therapy of Graves' disease patients.

The results of radioactive iodine (RAI) treatment for Graves' disease (GD) are related to the choice of diagnostic and dosimetry protocols, the steroid protection used, and the subsequent 131I dose. The effect of a high tissue-absorbed dose on the level of anti-thyroid antibodies (ATA) has been rarely considered. To estimate the effect of the first RAI therapy with a dose of 250 Gy on anti-thyreoperoxidase (anti-TPO) and anti-thyroid-stimulating hormone (TSH) receptor thyrotropin receptor antibody - TRAb levels in GD patients. The analysis encompassed 46 consecutive patients with clinical presentation of GD. We examined the serum levels of TSH, free thyroxine (FT4), anti-TPO, TRAb, thyroid volume (ThV), 131I effective half-life (EHL), introduction of steroid protection, levothyroxine dose used in thyroid replacement therapy - TRT, and effectiveness of treatment. As a result of RAI treatment, hypothyroidism was found in 35 patients (76.1%), euthyroidism in 7 patients (15.2%) and hyperthyroidism in 4 patients (8.7%). After RAI, we observed ThV reduction and increased anti-TPO (p = 0.001 and p = 0.001, respectively). It was found that a shorter EHL correlated with a higher baseline TRAb concentration and lower final anti-TPO serum concentration (p = 0.03 and p = 0.01, respectively). Lower final TRAb was found in patients with steroid protection (p = 0.049). Intergroup comparison of patients without steroid protection showed significantly higher final anti-TPO concentation (p = 0.02). Intergroup comparison of patients with TRT revealed significantly higher final anti-TPO concentration (p = 0.04). The application of a high absorbed dose of 250 Gy in GD resulted in high efficacy of RAI therapy at 1-year follow-up. An increased ATA level and its relationships with EHL and ThV reduction were observed at 1-year follow-up. There is a possible relationship between steroid protection and anti-TPO concentration.

Successful Management of Hyperthyroidism With Lithium and Radioiodine in a Patient With Previous Methimazole-Induced Agranulocytosis

Introduction: Antithyroid drug (ATD) therapy is the first-line treatment of Graves’ hyperthyroidism. Agranulocytosis, although rare, is a life-threatening condition associated with ATD therapy. For patients who recovered from ATD-induced agranulocytosis, surgery or radioiodine (RAI) therapy are adequate options to restore the patient’s euthyroid state. Here we report a case of ATD-related agranulocytosis where lithium therapy was used before RAI to control thyrotoxicosis and prevent worsening of hyperthyroidism. Case Report: A 74-year-old female with a previous history of hypertension presented with a 2-month history of weight loss (12 lbs), palpitations and shortness of breath. She was afebrile with a heart rate of 110, a blood pressure of 149/80, a fine tremor and a moderate diffuse goiter. She had a normal eye exam. Laboratory evaluation demonstrated TSH <0.01 uIU/mL (0.35-5.5), FT4 3.11 ng/dL (0.51-1.65) and TSH receptor antibody (TRAb) 40 (<1,0 U/L), consistent with thyrotoxicosis due to Graves’ disease. She was started on methimazole (MMI) 15mg and metoprolol. After four weeks, symptoms resolved and thyroid function tests (TFT) improved. However, after two months of treatment, she was hospitalized for fever, diarrhea and abdominal pain. White blood cell count (WBC) was 650/μL, and neutrophil count was 90/μL. A diagnosis of gastroenteritis and agranulocytosis was made and MMI was stopped. After seven days, symptoms resolved, the neutrophil count was 2200/ul and TFT were acceptable (FT4 1.25, ng/dL TT3 1.67 ng/ml, TSH < 0.02 uIU/mL). She was discharged without ATDs and a RAI dose of 20 mCi was scheduled. However, RAI therapy had to be postponed due to COVID-19 pandemic restrictions. After 3 weeks, TFT worsened and therapy with lithium carbonate 300 mg TID was started as the patient refused thyroidectomy. Lithium was initiated 12 days before RAI therapy and was maintained 7 days after the procedure. No side effects associated with lithium treatment were reported. TFT 7 days after RAI were FT4 1.43, ng/dL TT3 2.05 ng/ml and TSH < 0.02 uIU/mL. One month later, the patient was euthyroid without need for thyroid medication and remains on follow up. Discussion: Serum thyroid hormone (TH) concentrations usually increase after RAI therapy for Graves’ disease, a worrisome fact in patients with increased risk for cardiovascular complications. Previous studies report that pre-RAI treatment with lithium prevents changes in serum TH concentrations and enhances RAI therapy’s effectiveness. Here, treatment with lithium was used to control thyrotoxicosis and prevent further increase in TH levels associated with RAI therapy. Lithium is particularly suitable for patients with ATD-related side effects before definitive therapy (radioiodine or thyroidectomy). The antithyroid effect of lithium in this setting should be further studied.

Radioiodine therapy of Graves' disease.

Graves' disease (GD), the most common cause of hyperthyroidism, is an autoimmune disease directly caused by circulating autoantibodies that bind and activate the TSH receptor, inducing metabolic activation of the thyroid gland; this may be associated with important cardiac (atrial fibrillation) and ocular (ophthalmopathy) complications. Treating GD with real curative intent implies the full elimination of the functioning thyroid parenchyma using surgery or radioactive iodine therapy (RAI). RAI has been used in humans with hyperthyroidism since 1941, thanks to the pioneering work of a physician (Dr. Saul Hertz) and a physicist (Dr. Arthur Roberts). The rationale of RAI is based on the effect of radiation of 131I on target cells leading to DNA damage, both directly, through breakage of molecular bonds, and indirectly through the formation of free radicals. In particular, irradiation causes a broad spectrum of cellular damage due to the production of reactive oxygen species and lipid peroxidation of the plasma membrane. Thus, RAI-related cellular death takes place through both apoptosis and necrosis. The aim of this review was to summarize indications, efficacy, safety profile, and dosimetric aspects of RAI treatment in patients affected by GD.

Focus on radioiodine-131 biokinetics: the influence of methylprednisolone on intratherapeutic effective half-life of 131I during radioiodine therapy of Graves\u2019 disease

AimRadioiodine therapy (RIT) may trigger the development of Graves’ ophthalmopathy (GO) or exacerbate pre-existing subclinical GO. Therefore, glucocorticoid administration is recommended for patients with pre-existing GO. Aim of this study was to analyze the influence of glucocorticoid therapy with methylprednisolone on intratherapeutic effective half-life (EHL) of radioiodine-131 in patients with Graves’ disease (GD) as recent studies showed an effect for prednisolone.MethodsIn a retrospective study, 264 patients with GD who underwent RIT without any additional antithyroid medication were evaluated. Intrathyroidal EHL was determined pre- and intratherapeutically. Patients with co-existing GO (n = 43) received methylprednisolone according to a fixed scheme starting 1 day prior to RIT, patients without GO (n = 221) did not receive any protective glucocorticoid medication. The ratios of EHL during RIT and during radioiodine uptake test (RIUT) were compared.ResultsPatients receiving methylprednisolone showed a slight decrease of the mean EHL from 5.63 d (RIUT) to 5.39 d (RIT) (p > 0.05). A comparable result was obtained in patients without glucocorticoids (5.71 d (RIUT) to 5.47 d (RIT); p > 0.05). The ratios of the EHL between RIT and RIUT failed to show a significant difference between the two groups. EHL is therefore not significantly influenced by an additional protective treatment with methylprednisolone.ConclusionsIn the present study a decreased intrathyroidal EHL under glucocorticoid medication with methylprednisolone could not be detected. Therefore, co-medication with methylprednisolone in patients with GO may be preferred to avoid an intratherapeutic decrease of EHL by accompanying protective glucocorticoides.

Investigation of post-therapeutic image-based thyroid dosimetry using quantitative SPECT/CT, iodine biokinetics, and the MIRD\u2019s voxel S values in Graves\u2019 disease

BackgroundBefore radioiodine therapy for Graves’ disease, the estimated thyroid-absorbed dose is calculated based on various clinical parameters. However, the actual accumulation of iodine in the thyroid during radioiodine therapy is not determined. We validated the feasibility of post-therapeutic image-based thyroid dosimetry through quantitative single-photon emission computed tomography (SPECT) imaging and thyroid biokinetics and expanding the Medical Internal Radiation Dose Committee’s (MIRD) voxel dosimetry guidelines.MethodsForty-three patients with Graves’ disease who underwent radioiodine therapy were chosen as subjects for this retrospective analysis. We acquired patients’ SPECT images 24 h after oral administration. SPECT images were quantified using system volume sensitivity to calculate time-integrated activity coefficients on a voxel basis. Absorbed dose was obtained by convolving MIRD guideline voxel S values with time-integrated activity coefficients. To determine accuracy, we compared the results obtained using the post-therapeutic image-based absorbed-dose method (D̅image,PVC) with absorbed doses calculated using the method described by the European Association of Nuclear Medicine (pre-therapeutic method; DEANM).ResultsUsing image-based dosimetry as post-therapeutic dosimetry, we visualized the local accumulation and absorbed dose distribution of iodine in the thyroid. Furthermore, we determined a strong correlation (Pearson’s correlation coefficient = 0.89) between both dosimetries, using the regression equation: D̅image,PVC = 0.94 × DEANM + 1.35.ConclusionPost-therapeutic image-based doses absorbed in the thyroid resembled those of pre-therapeutic EANM method-based absorbed doses. Additionally, the post-therapeutic image-based method had the advantage of visualizing thyroid iodine distribution, thus determining local dose distributions at the time of treatment. From these points, we propose that post-therapeutic image-based dosimetry could provide an alternative to standard pre-therapeutic dosimetry to evaluate dose response.

Radioiodine therapy of Graves' disease and the uptake paradox

Purpose of the Study:Radioiodine (131I) therapy is approved and well-accepted modality for the treatment of hyperthyroidism. The dosage of 131I for successful treatment is based on many factors; however, an objective tool to determine the dose was missing. In a retrospective study, we found that high 131I uptake values required more dose to achieve desirable results contrary to the belief.Materials and Methods:Clinically and scintigraphically proven Graves' disease patients with high 131I uptake (>50%) were accrued for this study and block randomized into low-dose (Group I) and high-dose (Group II) groups. Low activity (5 mCi) was administered in Group I and higher activity (10 mCi) in Group II. The patients were followed up after 3 months with thyroid function tests to determine the outcome.Results:A total of 344 patients were analyzed at the end of 3 months, with 174 in low-dose group and 170 in high-dose group. Euthyroidism/hypothyroidism was achieved in significantly higher number of patients as compared to the low-dose group.Conclusion:The higher dose of 131I is required to achieve euthyroidism/hypothyroidism in patients with high 131I uptake.

MON-624 Follow-Up within the First Year after Radioiodine Therapy for Graves' Disease

MON-624 Follow-Up within the First Year after Radioiodine Therapy for Graves' Disease

A Case of Violent Suicide Attempt in a Context of Myxedema Psychosis following Radioiodine Treatment in a Patient with Graves’ Disease

Introduction Hypothyroidism has been associated with mood disorders but some cases of acute psychosis have also been reported. However, less attention has been paid to suicidal behavior in these patients. Case Report We report a case of suicide attempt by self-stabbing in a 43-year-old woman without past psychiatric history, four months after radioiodine therapy for Graves' disease. On clinical examination remarkable signs of myxedema were found and blood investigations showed hypothyroidism with an extremely high thyroid stimulating hormone (TSH) level (152 mUI/L; reference range 0.20-5.10). The patient presented delirium symptoms at the time of self-stabbing, which was associated with persecutory delusions and auditory harm command hallucinations. A rapid physical and psychiatric improvement was observed after the initiation of an oral thyroid replacement therapy without relapse after early discontinuation of the antipsychotic treatment. Discussion The most distinctive feature of our case is that the violent suicide attempt could be attributed to the myxedema psychosis. Suicide may result from several factors, including psychosocial stressors, psychiatric symptoms, and hormonal disturbance. This unique presentation should remind clinicians to systematically consider ordering additional tests in patients with atypical psychiatric presentation, even when serious behavioral disorders (such as violent suicide attempts) are present and may result in premature transfer to psychiatric units.

Radio-iodine therapy of Graves’ disease: is there a dose-effect relationship?

Radio-iodine therapy of Graves’ disease: is there a dose-effect relationship?

Low Dose Radioiodine Therapy for Graves' disease: comparison of outcomes following administration of different doses across two centres

Low Dose Radioiodine Therapy for Graves' disease: comparison of outcomes following administration of different doses across two centres

Predicting outcomes and complications following radioiodine therapy in Graves' thyrotoxicosis.

Radioiodine (RAI) is an effective treatment for Graves' thyrotoxicosis but is associated with a failure rate of 15% and may be a risk factor for thyroid eye disease (TED) and weight gain. We sought to examine predictors of RAI failure, weight gain, TED and patient satisfaction. Retrospective cohort study. A total of 655 episodes of RAI in Graves' thyrotoxicosis patients (2006-2015). Biochemical assessment, including TFTs and thyrotropin receptor antibodies (TRAb), clinical features (eg, TED, weight and thionamide use) and patient questionnaire. The treatment failure rate was 17%. Failure was greater with higher fT4 (P=0.002) and higher TRAb (P=0.004). Failure rate was 42.2% when TRAb >40U/L. Median weight gain was 3.2kg in those with normal fT4 prior to RAI and 5.8kg when fT4 was elevated (P<0.001). New TED developed in 7.6% but was not associated with post-RAI dysthyroidism. Treatment satisfaction was generally high (median response 8/10). Treatment failure after RAI occurs in predictable groups and this should be reflected in the information provided to patients. Weight gain is common and may not entirely be explained by a return to pre-thyrotoxic baseline. We were unable to detect any significant impact of post-RAI dysthyroidism on weight gain, TED or thyroid symptoms in this large cohort.

Clinical outcomes following radioiodine therapy in Graves' thyrotoxicosis

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Efficacy and safety of radioiodine treatment of Graves’ disease in children and adolescents

There are three methods in treatment of Graves’ disease in children and adolescents – antithyroid drugs, surgery and radioiodine therapy (RIT). However, treatment protocol of children and adolescents doesn’t exist. In the present case series study we have evaluated the effectiveness and safety of RIT in children and adolescents. We have observed totally 25 patients in age 11–17 years old (mean 14.8 years) with Graves’ disease. Ten patients were treated with RIT in Endocrinology Research Centre (Moscow) in 2016 year with activities 550–920 MBq. Follow-up period varied 6–11 months in this subgroup. The second subgroup (15 patients) was treated in radiology department in Nijniy Tagil rural hospital (Ural region) in the period 2005–2012 years. Follow-up period varied 3.5–11.5 years (mean 8.5 years). RIT was executed in all patients without any complications, direct or long-term. In two patients having endocrine ophtalmopathy in non-active phase it was no any signs of worsening in result of RIT. In 17 (68%) of 25 patients the hypothyroidism occurred through 6 months. In one case – euthyroidism. In remain 7 observations the hyperthyroidism recurred. Patient subgroups didn’t differ in mean age, gender ratio, thyroid size and autoantibodies to TSH receptor levels, but were differed in treatment 131I activities (subset from ERC – 550–920 MBq; subset from Nijniy Tagil – 168–400 MBq). However the treatment efficacy did not differ significantly (p = 0.99): 68% and 73%, accordingly. In conclusion, RIT of Graves’ disease in a safe and effective method of treatment for hyperthyroidism in children and adolescents. It’s necessary to prolong study in numerous patients cohort, longer-lasting follow-up period as well as to improve RIT efficiency.

Thymic Involution After Radioiodine Therapy for Graves Disease: Relationships With Serum Thyroid Hormones and TRAb.

Context:The mechanisms of thymic hyperplasia in Graves disease and its involution after radioiodine (I-131) therapy remain unknown.Objective:To examine whether computed tomography (CT) findings of the thymus in patients with Graves disease change before and 6 months after I-131 therapy and to elucidate factors that affect these changes.Design, Setting:A retrospective, single-center study was conducted. Thymic and thyroid volumes and thymic density were measured on CT. The associations of thymic volume or density with the following factors before I-131 therapy were examined: age; serum triiodothyronine (T3), thyroxine (T4), and thyroid-stimulating hormone receptor antibody (TRAb) levels; and thyroid volume. The changes in thymic volume and density and TRAb levels before and after I-131 therapy, and the correlations of thymic volume with T3 and T4 decline rates and TRAb changing rate and age were examined.Patients:We studied 40 consecutive patients with Graves disease who underwent neck and chest CT before and 6 months after I-131 therapy.Intervention:Observational study.Results:A significant negative correlation was observed only between thymic density and age before I-131 therapy. Thymic volume and density decreased and TRAb levels increased significantly after I-131 therapy. The thymic volume decline rate significantly positively correlated with serum T3 and thyroid volume decline rates. No significant correlation was found between thymic volume decline and TRAb changing rates.Conclusions:Significant thymic involution occurs after I-131 therapy in patients with Graves disease. Serum T3, but not TRAb, may be related to thymic hyperplasia and involution following I-131 therapy.

DYNAMIC CHANGES OF TRAb AND TPOAb AFTER RADIOIODINE THERAPY IN GRAVES' DISEASE.

To analyze the dynamic changes of serum thyrotrophin receptor antibody (TRAb) and thyroid peroxidase antibody (TPOAb) in Graves' disease (GD) patients before and after radioactive iodine (RAI) treatment and to investigate if TRAb and TPOAb play a role in the occurrence of early hypothyroidism after 131I therapy for Graves' hyperthyroidism. A total of 240 patients newly diagnosed with GD were selected to study. A clinical and laboratory assessment was performed before and at 3, 6, and 12 months after 131I therapy. Chemiluminescent immunoassays were used to detect serum free triiodothyronine (FT3), free thyroxine (FT4), sensitive thyroid-stimulating hormone (TSH) and TPOAb concentration. Radio-receptor assay was used to measure serum TRAb concentration. According to the early onset of hypothyroidism in a year after RAI therapy, patients were divided into early hypothyroidism group (group A) and non-early hypothyroidism group (group B). In both groups, serum TRAb and TPOAb increased at 3 months, reached the highest level at 6 months and returned to the baseline at 12 months after RAI therapy. TRAb showed a significant difference between the two groups at 6 months (P<0.01). Serum TPOAb in group A was higher than that in group B before and at 3, 6, 12 months after RAI therapy (P<0.05). Serum TRAb and TPOAb are closely related to the occurrence of the early hypothyroidism, and play an important role in judging prognosis after 131I treatment in Graves' disease.

The efficacy of immunosuppressive treatment of Graves' orbitopathy is not affected by previous anti-thyroid drugs or by radioiodine therapy of Graves' disease.

We studied the efficacy of immunosuppressive treatment of GO in a group of patients who had been treated with antithyroid drugs (the ATD group) and in another group that had undergone radioiodine therapy (the 131-I group). A total of 214 patients with exacerbation of GO were studied; the ATD group consisting of 168 patients, and the 131-I group consisting of 46 patients. All patients were treated with methylprednisolone IV pulses (total dose 8.0 g) followed by orbital irradiation (20 Gy in 10 fractions). CAS and IO indices, TSH, fT4, and TRAb levels were evaluated prior to, and 1, 6, and 12 months after treatment. One month after treatment the CAS index decreased significantly in both groups, against values before treatment, p < 0.05. In the ATD group the median level of TRAb-0 before treatment was 5.6 IU/L (min = 0.1; max = 114.0), and 12 months later (TRAb-12) it was 1.4 IU/L (min = 0.1; max = 75.3) (p < 0.05). In the 131-I group the median level of TRAb-0 was 14.3 IU/L (min = 0.6; max = 90.0) vs. TRAb-12 of 3.65 IU/L (min = 0.1; max = 41.0) (p < 0.05). In the ATD group the median value of IO-0 before treatment was 5.0 (min = 1.0; max = 12.0) vs. IO-12 of 2.0 (min = 0.0; max = 8.0) (p < 0.05). In the 131-I group the median value of IO-0 was 5.0 (min = 2.0; max = 9.0) vs. IO-12 of 2.0 (min = 0.0; max = 6.0) (p < 0.05). The severity of GO in the ATD and 131-I groups did not differ significantly over the course of observation despite differences noted in their TRAb levels. The efficacy of GO treatment did not differ between these groups. (Endokrynol Pol 2016; 67 (6): 554-561).

Impaired immune regulation after radioiodine therapy for Graves’ disease and the protective effect of Methimazole

Both therapies for Graves' disease (GD), radioactive iodine (RAI) and antithyroid drugs (ATD), were reported to have specific immune effects. We aimed at investigating the effects of RAI therapy on cellular subsets involved in immune regulation. We conducted a thirty day follow-up prospective cohort study of adult patients. Patients eligible for RAI therapy at our centre were approached. Twenty seven patients with GD were recruited, among whom 11 were treated with ATD. Twenty-two healthy subjects (HS) were also studied. Over time, frequency of regulatory T cells (Treg) and of invariant natural killer T cells (iNKT), along with Treg cell-mediated suppression and underlying mechanisms, were monitored in the peripheral blood. Variance in frequency of Treg and iNKT after RAI therapy was higher in GD patients than in HS over time (p<0.0001). Reduced Treg suppressive function was observed after RAI therapy in GD patients (p=0.002). ATD medication prior to RAI dampened these outcomes: less variation of Treg frequency (p=0.0394), a trend toward less impaired Treg function, and prevention of reduced levels of suppressive cytokines (p<0.05). Shortly after RAI therapy, alterations in immunoregulatory cells in patients with GD were observed and partially prevented by an ATD pretreatment. Worsening of autoimmunity after RAI was explained in previous studies by enhanced immune activity. This study adds new highlights on immune regulation deficiencies after therapeutic interventions in thyroid autoimmunity.