Increased thyroidal T4/T3 ratio in nodular and paranodular tissues of nontoxic goiter following suppressive treatment with thyroid hormones

The effect of suppressive treatment with thyroid hormones on thyroidal iodothyronines and T4/T3 ratio in nodular and paranodular tissues was investigated in 12 patients with nontoxic goiter. Results were compared to those from 11 nontreated patients. Continuous thyroid hormone administration produced a significant increase in thyroidal T4 and T4/T3 ratio in nodular tissues while T3 remained unchanged. In paranodular tissues a significant rise of T4/T3 ratio, an insignificant increase in T4 and a decrease in T3 were observed following the administration of thyroid hormones. The results are very similar to those obtained in paranodular tissue of autonomously functioning thyroid nodule, and are probably the consequence of suppressed TSH secretion, as TSH predominantly stimulates the synthesis of T3 and/or thyroidal T4 monodeiodination.     

Ultrasonographic and scintigraphic studies of "hot" autonomic thyroid nodules

Scintigraphic and gammagraphic (gamma-camera) techniques have been applied in diagnosing "hot" non-TSH dependent thyroid nodules. On the basis of frequent uneven accumulation of isotopic tracer observed in scintigraphic studies it was concluded that the structure of these nodules is heterogeneous. In some cases paradoxical patterns have been obtained following the dynamic tests of suppression and stimulation of the thyroid: after the administration of thyroid preparations paranodular thyroid tissue appears, while TSH administration causes an increase in the iodine uptake by the nodule. Ultrasonographic and gamma-camera studies have been carried out in 50 cases of "hot" autonomic thyroid nodules previously diagnosed by scintigraphy. Ultrasonographic studies revealed a weaker echogenicity in some cases and an intensified echo in the other. Sometimes by using this technique it was possible to demonstrate the occurrence of heterogeneous structures suggesting a cystic degeneration of the nodule. Paranodular thyroid tissue, invisible in scintigraphic scanning, could usually be observed by applying gamma-camera. It was concluded that both gamma camera and ultrasonographic studies confirm heterogeneous structure of intranodular tissue producing paradoxical patterns in scintigraphic scanning, with the latter technique usually aiding the detection of paranodular thyroid tissue without the necessity of application of the TSH test.     

A radioecological model for thyroid dose reconstruction of the Belarus population following the Chernobyl accident

A radioecological model was developed to estimate thyroid exposures of the Belarus population following the Chernobyl accident. The input of the model includes an extensive data set of the ¹³⁷Cs activity per unit area deposited during the Chernobyl accident, the rainfall data for different regions of Belarus, the ¹³¹I/¹³⁷Cs ratio in the deposit and the start of the grazing period in Belarus in April/May 1986. The output of the model is the age-dependent thyroid exposure due to the intake of ¹³¹I with fresh milk. Age-dependent average thyroid doses were assessed for selected regions of Belarus. The maximum thyroid doses were estimated for the inhabitants of Gomel oblast where the highest deposition was observed among the regions considered here. The lowest doses were estimated for Vitebsk oblast with the lowest level of depositions. The mean exposures for the oblasts of Grodno, Minsk, Mogilev and Brest were very similar. The results were compared with estimations of thyroid exposure that were based on ¹³¹I measurements in human thyroids, and they are in good agreement. The model may be used for the assessment of thyroid doses in Belarus for areas where no ¹³¹I measurements are available.     

Risk Factors for Nonremission and Progression-Free Survival after I-131 Therapy in Patients with Lung Metastasis from Differentiated Thyroid Cancer: A Single-Institute,Retrospective Analysis in Southern China

Objective: Prognostic factors related to progression-free survival (PFS) have not received much attention in the literature regarding iodine-131 (¹³¹I) therapy for patients with differentiated thyroid cancer and lung metastases. We sought to explore the factors associated with PFS and nonremission in a group of patients with differentiated thyroid cancer and pulmonary metastases at initial diagnosis and to investigate the impact of ¹³¹I therapy on pulmonary function and peripheral blood counts in the same cohort of patients.Methods: The medical records of 1,050 patients with differentiated thyroid cancer treated at the Zhujiang Hospital of Southern Medical University from January 2006 to January 2015 were retrospectively reviewed. Among them, 107 patients fulfilled the inclusion criteria.Results: Multivariate Cox regression analysis indicated that age ≥45 years and ¹³¹I nonavidity were independent risk factors for disease progression. Multivariate logistic regression analysis revealed that pulmonary nodule size ≥1 cm and ¹³¹I nonavidity were the strongest risk factors predicting nonremission. Varying cumulative ¹³¹I dosage had no association with posttreatment pulmonary function or peripheral blood cell counts.Conclusion: Similar to earlier studies, our results confirm that ¹³¹I nonavidity was associated with an increased risk of disease progression and greater odds of nonremission. In addition, patients with differentiated thyroid cancer and lung metastases with pulmonary nodules ≥1 cm had a reduced likelihood of achieving remission. Furthermore, special attention is needed when monitoring patients over 45 years at a higher risk of disease progression.Abbreviations:CI = confidence intervalDTC = differentiated thyroid cancer¹⁸F-FDG = fluoro-18 fluorodeoxyglucoseFEF = forced expiratory flowFTC = follicular thyroid cancerFVC = forced vital capacityGR = granulocytesHb = hemoglobinHR = hazard ratio¹³¹I = iodine-131LN = lymph nodeOR = odds ratioOS = overall survivalPET/CT = positive positron emission tomography/computed tomographyPFS = progression-free survivalPT = partial thyroidectomyPTC = papillary thyroid cancerRAI = radioactive iodineRBC = red blood cellTg = thyroglobulinTgAb = thyroglobulin antibodyTSH = thyroid-stimulating hormoneTT = total thyroidectomyWBC = white blood cellsWBS = whole body scan     

Hypermethylated RASSF1 and SLC5A8 promoters alongside BRAFV600E mutation as biomarkers for papillary thyroid carcinoma

Circulating cell-free DNA (cfDNA) has been considered as a diagnostic source to track genetic and epigenetic alterations in cancer. We aimed to study mutation in addition to the methylation status in the promoter regions of RASSF1 and SLC5A8 genes in tissues and circulating free DNA samples of patients affected with papillary thyroid carcinoma (PTC) and thyroid nodules as controls. BRAF^V600E mutation was studied by ARMS-scorpion real-time polymerase chain reaction method in 57 PTC and 45 thyroid nodule cases. Methylation status of RASSF1 and SLC5A8 promoter regions was analyzed by methylation-specific high-resolution melting curve analysis. BRAF^V600E mutation was found in 39 (68.4%) out of 57 PTC tissue samples, while in 33 (49.1%) cases of cfDNA, this mutation was detected. The frequency of BRAF^V600E mutation in cfDNA was significantly different between metastatic and nonmetastatic PTC cases (22 of 33 PTC cases vs. 5 of 34 thyroid nodule samples). Methylation levels of three promoter regions of SLC5A8 and proximal promoter region of RASSF1 was significantly different between PTC and thyroid nodule cases in both cfDNA and tissue DNA. In addition, the methylation status of these two genes in tissue DNA was reflected in methylation status observed in cfDNA. This study confirmed that BRAF^V600E mutation is better for discrimination between papillary thyroid carcinoma and thyroid nodules. On the other hand, hypermethylation in the more proximal promoter regions to RASSF1 and SLC5A8 genes showed higher sensitivity and more acceptable specificity for this discrimination.     

Estimated Dietary Intake of Radionuclides and Health Risks for the Citizens of Fukushima City,Tokyo, and Osaka after the 2011 Nuclear Accident

The radionuclides released from the Fukushima Daiichi nuclear power plant in 2011 pose a health risk. In this study, we estimated the 1st-year average doses resulting from the intake of iodine 131 (¹³¹I) and cesium 134 and 137 (¹³⁴Cs and ¹³⁷Cs) in drinking water and food ingested by citizens of Fukushima City (∼50 km from the nuclear power plant; outside the evacuation zone), Tokyo (∼230 km), and Osaka (∼580 km) after the accident. For citizens in Fukushima City, we considered two scenarios: Case 1, citizens consumed vegetables bought from markets; Case 2, citizens consumed vegetables grown locally (conservative scenario). The estimated effective doses of ¹³⁴Cs and ¹³⁷Cs agreed well with those estimated through market basket and food-duplicate surveys. The average thyroid equivalent doses due to ingestion of ¹³¹I for adults were 840 µSv (Case 1) and 2700 µSv (Case 2) in Fukushima City, 370 µSv in Tokyo, and 16 µSv in Osaka. The average effective doses due to ¹³⁴Cs and ¹³⁷Cs were 19, 120, 6.1, and 1.9 µSv, respectively. The doses estimated in this study were much lower than values reported by the World Health Organization and the United Nations Scientific Committee on the Effects of Atomic Radiation, whose assessments lacked validation and full consideration of regional trade in foods, highlighting the importance of including regional trade. The 95th percentile effective doses were 2–3 times the average values. Lifetime attributable risks (LARs) of thyroid cancers due to ingestion were 2.3–39×10⁻⁶ (Case 1) and 10–98×10⁻⁶ (Case 2) in Fukushima City, 0.95–14×10⁻⁶ in Tokyo, and 0.11–1.3×10⁻⁶ in Osaka. The contributions of LARs of thyroid cancers due to ingestion were 7.5%–12% of all exposure (Case 1) and 12%–30% (Case 2) in Fukushima City.     

Correlation between Long-acting Thyroid Stimulator Protector Level and Thyroid 131I Uptake in Thyrotoxicosis

Out of 50 consecutive untreated patients with diffuse toxic goitre 15 showed long-acting thyroid stimulator (LATS), 30 showed LATS protector only, and five showed neither. LATS protector was present in all the patients with LATS. Infiltrative ophthalmopathy was less common in patients with LATS protector only (40%) than in patients with LATS also (67%), but the difference was not significant. There was a correlation between LATS protector level and thyroid ¹³¹I uptake rate factor (k₁), the coefficient (r) being 0·68 (P < 0·001). LATS level showed no such correlation. The results support the hypothesis that LATS protector is a pathogenic thyroid stimulator in patients with diffuse toxic goitre.     

Thyroid carcinoma in children and adolescents: a retrospective review

ObjectiveTo describe clinical presentation, preoperative study, intervention, histology, surgical complications and follow-up characteristics, and survival in patients with thyroid carcinoma (TC) with less than 18 years at presentation.Material and methodsretrospective analysis of clinical data of all children and adolescents followed in S. João Hospital from January 1, 2000 to March 31, 2010 with histologic diagnosis of TC.ResultsTwenty-three patients were identified, 19 girls, and 4 boys. Median age at presentation was 17.0 years. Annual incidence was 2.3 cases/year. The main presenting symptom was a solitary thyroid nodule (60.8%). Three (13%) patients had risk factors for TC, 2 of the 3 had previous cervical irradiation. The other was a smoker. Total thyroidectomy was performed in 16 (69.6%), and 10 patients underwent a second surgical procedure. Four (17.4%) patients had postoperative complications. Histologic examination revealed differentiated TC in all, papillary thyroid carcinoma (PTC) in 86.9%, follicular carcinoma in the remaining. All patients received thyroxine suppressive therapy and 20 underwent therapeutic radioactive iodine (¹³¹I). During follow-up (7.1 years), 7 out of the 23 patients presented new metastases and needed new treatment. All patients are currently alive.ConclusionsTC is a reality in pediatric population, thyroid routine examination should take part in all clinical examination in children and adolescents.     

The Purity of Radioiodide-I131 Assessed by in Vivo and in Vitro Methods

Between 41 and 94% of the radioactivity of 24 preparations of I¹³¹ supplied without cysteine preservative was non-iodide on chromatographic analysis. Extraneous radio-activity was essentially absent from I¹³¹ supplied with cysteine. It was converted to iodide-I¹³¹ by 10^-3 M cysteine or iodide but not by incubation at pH 2. The average thyroid uptake of I¹³¹ containing extraneous radioactivity was significantly lower than the uptake of I¹³¹ free from non-iodide impurity in 16 human subjects measured under controlled conditions and in a random group of 669 patients. Incubation of samples of I¹³¹ containing non-iodide radioactivity with tyrosine and cupric chloride resulted in the non-enzymatic formation of monoiodotyrosine-I¹³¹ either in the presence or absence of thyroid homogenate. Enzymatic formation of monoiodotyrosine-I¹³¹ by thyroid homogenates could be demonstrated only when I¹³¹ free from extraneous activity was used.     

Influence of initial large dose on subsequent uptake of therapeutic radioiodine in thyroid cancer patients

Fifty-two patients with differentiated thyroid cancer, following thyroidectomy were studied by administering a quantity of up to 5 mCi of [¹³¹I]sodium iodide. In most of these patients, radioiodine uptake values obtained with the subsequent therapeutic dose were markedly lower than those observed with the initial doses. This observation was verified in seven of the patients with differentiated thyroid cancer, by measuring the radioiodine uptake with a second dose of 4.5 mCi of [¹³¹I]sodium iodide. Calculations showed that the major etiology was probably therapeutic irradiation of the thyroid by the first dose.     

HYPERTHYROIDISM—Diagnosis by Failure of Triiodothyronine to Suppress Uptake of Iodine131

Sixty patients with abnormally high I¹³¹ uptake were treated with liothyronine (L-triiodothyronine) for seven or eight days and then tested again. Fifty-five patients showed a suppression of iodine uptake sufficient to eliminate the possibility of hyperthyroidism. Also the therapeutic trial of liothyronine indicated whether they were euthyroid, or hypothyroid with iodine deficiency. Six of the patients showed insignificant change in the I¹³¹ uptake after treatment with thyroid hormone—that is, the change from the original uptake was less than 30 per cent. These six patients were later confirmed to be hyperthyroid. In four patients the uptake at the second test was less by between 35 and 52 per cent than at the first. These four patients, like the remainder with even greater suppression in thyroid uptake, remained clinically euthyroid.The repeat I¹³¹ uptake test was thus seen to be considerably more accurate than the single test and well worth the time required to perform it.     

Effect of Post-Surgical Rai Therapy on Parathyroid Function in Patients with Differentiated Thyroid Cancer

Objective: Radiotherapy with radioactive iodine (RAI) has become a common treatment for postsurgical differentiated thyroid carcinoma (DTC). The objective of this study was to determine the effect of RAI therapy following surgery on the function of the parathyroid glands in DTC patients.Methods: A total of 81 DTC patients who received RAI therapy after surgery were enrolled in the study. The size of the residual thyroid was detected by technetium-99m (^99mTc)-pertechnetate thyroid scan (^99mTc thyroid scan) before RAI therapy. The iodine uptake ability of residual thyroid was evaluated by iodine-131 (¹³¹I) whole-body scan (WBS). All patients were treated with an activity of 3.7 GBq (100 mCi) ¹³¹I. Parathyroid hormone (PTH), serum calcium, phosphorus, and magnesium were evaluated at 1 day before treatment, and at 1 month and 3 months after treatment.Results: The results show that there was no statistically significant difference in blood PTH level observed (P>.05) between 3 time points (pre-treatment, 1 month post-treatment and 3 months post-treatment). The serum calcium and phosphorus did not change significantly (P>.05), but serum magnesium level was elevated after treatment (P<.05). There were no significant differences between PTH changes and sex, age, scores of ^99mTc thyroid scan, scores of ¹³¹I WBS, Tumor (T) stage, and Node (N) stage.Conclusion: RAI therapy following surgery did not significantly affect parathyroid function in DTC patients.Abbreviations: ATA = American Thyroid Association; DTC = differentiated thyroid carcinoma; FT3 = free triiodothyronine; FT4 = free thyroxine; 131I = iodine-131; PTH = parathyroid hormone; RAI = radioiodine; 99mTc = Technetium-99m; TG = thyroglobulin; TNM = Tumor Node Metastasis; TSH = thyroid-stimulating hormone; WBS = whole-body scan     

Thyroid doses in Ukraine due to 131I intake after the Chornobyl accident. Report II: dose estimates for the Ukrainian population

This paper describes the revision of the thyroid dosimetry system in Ukraine using new, recently available data on (i) revised ¹³¹I thyroid activities derived from direct thyroid measurements done in May and June 1986 in 146,425 individuals; (ii) revised estimates of ¹³¹I ground deposition density in each Ukrainian settlement; and (iii) estimates of age- and gender-specific thyroid masses for the Ukrainian population. The revised dosimetry system estimates the thyroid doses for the residents of the settlements divided into three levels depending on the availability of measurements of ¹³¹I thyroid activity among their residents. Thyroid doses due to ¹³¹I intake were estimated in this study for different age and gender groups of residents of 30,353 settlements in 24 oblasts of Ukraine, Autonomous Republic Krym, and cities of Kyiv and Sevastopol. Among them, dose estimates for 835 settlements were based on ¹³¹I thyroid activities measured in more than ten residents (the first level), for 690 settlements based on such measurements done in neighboring settlements (the second level), and for 28,828 settlements based on a purely empirical relationship between the thyroid doses due to ¹³¹I intake and the cumulative ¹³¹I ground deposition densities in settlements (the third level). The arithmetic mean of the thyroid doses due to ¹³¹I intake among 146,425 measured individuals was 0.23 Gy (median of 0.094 Gy); about 99.8% of them received doses less than 5 Gy. The highest oblast-average population-weighted thyroid doses were estimated for residents of Chernihiv (0.15 Gy for arithmetic mean and 0.060 Gy for geometric mean), Kyiv (0.13 and 0.051 Gy) and Zhytomyr (0.12 and 0.049 Gy) Oblasts followed by Rivne (0.10 and 0.039 Gy) and Cherkasy (0.088 and 0.032 Gy) Oblasts, and Kyiv City (0.076 and 0.031 Gy). The geometric mean of thyroid doses estimated in this study for the entire Ukraine essentially did not change in comparison with a previous estimate, 0.020 vs. 0.021 Gy, respectively. The ratio of geometric mean of oblast-specific thyroid doses estimated in the present study to previously calculated doses varied from 0.51 to 3.9. The highest increase in thyroid doses was found in areas remote from the Chornobyl nuclear power plant with a low level of radioactive contamination: by 3.9 times for Zakarpatska Oblast, 3.5 times for Luhansk Oblasts and 2.9 times for Ivano-Frankivsk Oblast. The developed thyroid dosimetry system is being used to revise the thyroid doses due to ¹³¹I intake for the individuals of post-Chornobyl radiation epidemiological studies: the Ukrainian-American cohort of individuals exposed during childhood and adolescence, the Ukrainian in utero cohort, and the Chornobyl Tissue Bank.

     

Radiation dose rates of differentiated thyroid cancer patients after <Superscript>131</Superscript>I therapy

Postoperative ¹³¹I treatment for differentiated thyroid cancer (DTC) can create a radiation hazard for nearby persons. The present prospective study aimed to investigate radiation dose rates in ¹³¹I-treated DTC patients to provide references for radiation protection. A total of 141 ¹³¹I-treated DTC patients were enrolled, and grouped into a singular treatment (ST) group and a repeated treatment (RT) group. The radiation dose rate of ¹³¹I-treated patients was measured. The rate of achieving discharge compliance and restricted contact time were analyzed based on Chinese regulations. Multivariate logistic regression analysis was used to analyze the independent factors associated with the clearance of radioiodine. The rate of achieving discharge compliance (¹³¹I retention <?400 MBq) was 79.8 and 93.7% at day 2 (D2) for the ST and RT groups, respectively, and reached 100% at D7 and D4, respectively. The restricted contact time with ¹³¹I-treated patients at 0.5 m for medical staff, caregivers, family members, and the general public ranged from 4 to 7 days. Multivariate logistic regression analysis showed that the 24-h iodine uptake rate was the only significant factor associated with radioiodine clearance. For the radiation safety of ¹³¹I-treated DTC patients, the present results can provide radiometric data for radiation protection.     

Residualizing and non-residualizing analogues of low-density lipoprotein as iodine-123 radiopharmaceuticals for imaging LDL catabolism

Low-density lipoprotein (LDL) labeled via direct iodination or via the radioiodinated residualizing moiety tyramine-cellobiose (TC) were compared in rabbits as potential ¹²³I radiopharmaceuticals for imaging sites of LDL catabolism. The tissue deposition of ¹³¹I-TC-LDL after 24 h as determined by dissection was in the major catabolic organs (liver, adrenals, spleen), and its plasma clearance was slower in rabbits with dietary hypercholesterolemia than in normals. ¹³¹I-LDL was unsuitable as a metabolic tracer due to redistribution of catabolites and/or loss of the label before protein degradation, which resulted in little accumulation of radioactivity in catabolic organs and high thyroid uptake. The plasma clearance half-time was similar (ca 22 h) for the two compounds in normal rabbits, but was increased to about 36 h for ¹³¹I-TC-LDL and decreased to approximately 9 h for ¹³¹I-LDL in hypercholesterolemic animals. The were similar with dynamic imaging of control and hypercholesterolemic rabbits using ¹²³I-labeled analogues. ¹²³I-TC-LDL rapidly localized in the liver, with low thyroid accumulation of radioactivity. The hepatic uptake of ¹²³I-LDL was about half that of ¹²³I-TC-LDL, and thyroid sequestration of radioactivity was significant for ¹²³I-LDL but not ¹²³I-TC-LDL. These data suggest that whereas the residualizing ¹²³I-TC-LDL has a pharmacokinetic profile representative of lipoprotein metabolism, the biodistribution of the activity from injected ¹²³I-LDL is complicated by processes other than protein degradation. The results are discussed with regard to nuclear medicine applications in evaluating lipoprotein catabolism in man.     

Intrathyroidal Ectopic Thymic Tissue Mimicking Thyroid Cancer in Children

ObjectiveTo increase awareness of the important differential diagnosis between thyroid cancer and intrathyroidal ectopic thymic tissue when performing neck ultrasound (US) in pediatric patients.MethodsWe report 2 cases of intrathyrodal thymic tissue that were initially referred as possible papillary thyroid cancer (PTC). US and cytologic features of these lesions are described, and the distinguishing US characteristics of intrathyroidal thymic tissue versus PTC are discussed.ResultsTwo pediatric patients who underwent thyroid US were diagnosed with thyroid nodules suggestive of PTC. The suspected lesions in both patients exhibited an echo texture identical to the normal thymus gland. Fine-needle aspirate (FNA) biopsy of the nodule in the first case revealed numerous lymphocytes with positive immunocytochemical staining for CD3, confirming a T cell phenotype. The second patient underwent follow-up US imaging 8 months later that showed stability of the intrathyroidal nodule.ConclusionIntrathyroidal ectopic thymic tissue can be mistaken for PTC as both conditions have similar US features. Increased awareness of this unique mimicry may help to avoid unnecessary invasive investigations and surgery in these young patients. (Endocr Pract. 2014;20: e241-e245)     

Apport de l’imagerie hybride TEMP-TDM dans le suivi d’un cancer différencié de la thyroïde

In the management of patients with differentiated thyroid cancer (DTC), abnormalities detected on planar whole body scan and ¹³¹I-SPECT are difficult to interpret because of a lack of anatomical landmarks and limited specificity. Integrated ¹³¹I-SPECT-CT imaging has an additional value for characterization of equivocal tracer uptake seen on planar imaging as well as for precise localization. We illustrate through an observation the incremental diagnostic value of ¹³¹I-SPECT-CT images in the diagnosis of a cervical lymph node mimicking a physiological uptake on planar views. A 35-year-old Tunisian female was followed for papillary thyroid carcinoma, for which she underwent total thyroidectomy and iratherapy. Three years after a complete remission, the thyroglobulin (Tg) level on TSH stimulation increased. Diagnostic planar images with ¹³¹I did not disclose any obvious pathological foci. Furthermore, we noticed an increased ¹³¹I-uptake in the left sub-mandibulary area, which suggested a salivary physiological activity. SPECT-CT of the neck and chest were then performed with a Symbia T camera. Fused images demonstrate that this activity corresponds to a cervical lymph node closely adjacent to sub-mandibulary gland. Management of the patient was then changed. In selected patients with DTC, hybrid imaging should be used as a complementary to planar imaging in terms of diagnostic accuracy, because of superior focus localization and additional anatomic information derived from the CT component. Integrated SPECT-CT is then a useful tool, especially in cases of unclear diagnoses, precising anatomical localization of areas of increased ¹³¹I-uptake and distinguishing malignant lesions from normal physiological uptakes. This is particularly important in an oncologic center, as ours, where we don’t yet have a positron emission tomography (PET) camera is not yet available.     

Long-Term Outcomes of Radioiodine Therapy for Juvenile Graves Disease with Emphasis on Subsequently Detected Thyroid Nodules: A Single Institution Experience from Japan

Objective: To investigate the long-term outcomes of radioiodine therapy (RIT) for juvenile Graves disease (GD) and the ultrasonographic changes of the thyroid gland.Methods: All of 117 juvenile patients (25 males and 92 females, aged 10 to 18 &lsqb;median 16] years) who had undergone RIT for GD at our clinic between 1999 and 2018 were retrospectively reviewed. Each RIT session was delivered on an outpatient basis. The maximum ¹³¹I dose per treatment was 13.0 mCi, and the total ¹³¹I dose per patient was 3.6 to 29.8 mCi (median, 13.0 mCi). ¹³¹I administration was performed once in 89 patients, twice in 26, and three times in 2 patients. Ultrasonography of the thyroid gland was regularly performed after RIT. The duration of follow-up after the initial RIT ranged from 4 to 226 (median 95) months.Results: At the latest follow-up more than 12 months after RIT (n = 111), the patients' thyroid functions were overt hypothyroidism (91%), subclinical hypothyroidism (2%), normal (5%), or subclinical hyperthyroidism (2%). New thyroid nodules were detected in 9 patients, 4 to 17 years after initial RIT. Patients with newly detected thyroid nodules underwent RIT with lower doses of ¹³¹I and had larger residual thyroid volumes than those without nodules. None of the patients were diagnosed with thyroid cancer or other malignancies during the follow-up period.Conclusion: Over a median follow-up period of 95 months (range, 4 to 226 months), RIT was found to be effective and safe in juvenile GD. However, cumulative evidence from further studies is required to confirm the long-term safety of RIT for juvenile GD.Abbreviations: ATD = antithyroid drug; GD = Graves disease; KI = potassium iodide; LT4 = levothyroxine; MMI = methimazole; PTU = propylthiouracil; RAIU = radio-active iodine uptake; RIT = radioiodine therapy; ^99mTc = technetium-99m; TSH = thyrotropin     

Astatine (211At) as a therapeutic radionuclide. The plasma: Blood cell distribution in vitro

Therapy of carcinoma of the thyroid may include the use of the radionuclide ¹³¹I, which localizes to thyroid tissue. In considering the use of another halogen, the α particle emitting radionuclide astatine, ²¹¹At, there is also the requirement that it too can be taken up by the thyroid. However, in view of its short half-life (7.2 h) it is important that its transport in the blood is not a factor likely to render it less available. For example, retention of ²¹¹At by red cells may retard its uptake by the thyroid. This in vitro in-vestigation of the partitioning of the ²¹¹At between erythrocytes and plasma indicates that it is not strongly bound by the red cells in blood.