24-hour Radioactive Iodine Uptake Research Articles

FRI557 Don’t Forget The Incidental Thyroid Nodule In Graves’ Disease. A Case of Marine-Lenhart Syndrome

Abstract Disclosure: K.N. Andino-Lebrón: None. A. Martinó-Morales: None. J.M. Colón-Castellano: None. Marine-Lenhart syndrome (MLS) was initially described by Charkes in 1972 as he observed patients with Graves’ disease (GD) and incidental functioning thyroid nodules. He named the disease Marine-Lenhart syndrome based on a paper published by Marine and Lenhart in 1911. MLS is a variant of GD now described as the coexistence of GD and autonomous functional thyroid nodules (AFTN); thus, patients present with thyrotoxicosis due to GD and AFTN. MLS is very rare, and prevalence is estimated to be around 0.8%-2.7%. Here, we present a case of MLS in a 79-year-old female. A 79-year-old Hispanic woman with history of breast metaplasia s/p chemoprevention with tamoxifen for 5 years, atrial premature contractions on metoprolol, among other medical conditions was referred to Endocrinology clinics by her primary care physician (PCP) because of abnormal thyroid function tests and ultrasound. She reported feeling anxious with associated palpitations, she denied weight loss. Physical examination was remarkable for regular rate and rhythm, no goiter, no palpable nodules, no proptosis, and deep tendon reflexes +1. Laboratory testing revealed a suppressed TSH of 0.224 uIU/mL, normal free T4 at 1.17 ng/dL, normal total T3 at 142.5 ng/dL, and positive thyroid stimulating immunoglobulins at 345%. Thyroid ultrasound showed a normal size gland with multiple complex nodules. In the right lobe there was a mixed cystic and solid nodule, measuring 1.48x1.21x1.71cm, wider than tall, with internal vascularity and punctate calcifications. In the left lobe there was an isoechoic and solid nodule measuring 0.7x0.5x0.7cm, wider than tall, without calcifications. Thyroid uptake scan with SPECT-CT demonstrated a focus of increased tracer uptake on the upper pole of the right thyroid lobe that corresponds to the one found on CT scan and a diminished and nonuniform uptake of the tracer in the reminders of the thyroid gland. The 24-hour radioactive iodine uptake was 17.5%. Diagnosis of MLS was made, and the patient was started on methimazole 5mg daily, which she has been tolerating well. Follow up laboratories show a biochemically euthyroid state. Marine-Lenhart syndrome is a rare entity of Graves’ disease which is currently defined as GD and accompanying functioning nodule(s). To establish the diagnosis, it is important the evaluation with scintigraphy and autoimmune testing. Multiple treatment options are available and patients with GD should be evaluated for the presence of thyroid nodules and their functional status to achieve optimal therapy. Patients with GD have a chance of remission when treated with antithyroid drugs. Due to the pathophysiology of AFTN, patients with MLS (concurrent GD and AFTN) have lower remission rates with antithyroid drugs and may require definitive management therapy with radioactive iodine or surgery. Presentation: Friday, June 16, 2023

Relation between surgical oncologic quality indicators for papillary thyroid cancer.

Background:It remains unclear how thyroid surgical oncologic quality indicators (TSOQIs) are related to each other, and how to best interpret and apply these measures within the context of surgical quality assurance. We aimed to examine the relation between 3 TSOQIs: postoperative serum thyroglobulin level, 24-hour radioactive iodine uptake (RAIU) and metastatic lymph node ratio (MLNR).Methods:We conducted a retrospective review of patients who underwent total thyroidectomy for treatment of papillary thyroid cancer (PTC) performed by a single high-volume thyroid surgeon at a tertiary referral centre between 2012 and 2017. To establish the strength of correlation between pairs of quality indicators and the MACIS (metastasis, age, completeness of resection, invasion and size) prognostic score, we performed tests of normality and used the Spearman correlation coefficient to determine the correlation of nonnormal data containing outliers.Results:A total of 139 patients with PTC were included in the study. Their mean MACIS score was 5.0 (standard deviation 1.5). Fifteen patients had high-risk thyroid cancer (MACIS score > 6.99). A weak correlation was found between serum thyroglobulin level and RAIU (rs = 0.27, p = 0.006) and a moderate correlation was found between serum thyroglobulin level and MLNR (rs = 0.40 p = 0.002). A weak correlation between serum thyroglobulin level and MACIS score was also observed (rs = 0.20, p = 0.05).Conclusion:Based on our findings, we propose that the postoperative serum thyroglobulin level represents the quality metric that has the most clinical utility because it is measurable in all patients and also correlates with both RAIU and MLNR. With further research, surgeons seeking to evaluate the oncologic quality of thyroidectomy performed for PTC may consider applying a quality indicator to their future practice.

Frequency of Pathological Types of Hyperthyroidism in Thyroid Scan Patients.

Hyperthyroidism is a common systemic disorder where Graves' disease is known as the leading cause of the disease. Thyroid stimulating hormone, T4 and T3 antibody assay is usually performed for the diagnosis of the pathology. However, with uncertainty in the results and in order to estimate the magnitude and the exact cause of the disease, radioactive iodine uptake (RAIU) test is recommended. The aim of this study is to evaluate underlying pathology in the patients presenting hyperthyroidism using RAIU test results. This is a cross-sectional retrospective study conducted on the patients with hyperthyroidism referred to Shahid Madani Hospital in Khorramabad. Data regarding the biochemical analysis and RAIU test was collected from the records and a questionnaire based on demographic and clinical information was completed for each patient. Of 137 patients presenting hyperthyroidism, 62.04% presented with Graves' disease, 24.08% with toxic multinodular goiter and 13.86% with toxic adenoma. 24-hour RAIU test showed that the percent of radioiodine uptake was most in toxic adenoma with 67.7%, Graves' disease 53.5% and multinodular goiter 39%, respectively. From the age-based analysis, we found that Graves' was most common in 20-30 years old individuals accounting for 34%, multinodular goiter in 50+ aged individuals with 36.3% and toxic adenoma was most prevalent in 30-40 and 50+ aged patients, with 26.3%. In our population of interest, 81.8% toxic multinodular goiter patients were females. Our study presents the outcome of RAIU tests in hyperthyroidism based on the underlying pathologies. We also conclude, in light of other findings, that Graves' disease is the most common cause of hyperthyroidism in our population.

SAT-464 A Case of Impending Thyroid Storm in a Patient with Subacute Thyroiditis Following an Influenza Vaccine

Introduction: Thyroid storm is a rare, potentially fatal condition, affecting 1% of individuals with thyrotoxicosis. Although it can theoretically be seen in any cause of thyrotoxicosis, the most likely underlying etiology is Graves’ disease. The rarity of thyroid storm due to thyroiditis makes the diagnosis challenging as the clinical and biochemical features overlap Grave’s disease. Here we describe a rare case of severe thyrotoxicosis in a woman due to subacute thyroiditis that developed after receiving an influenza vaccine.Case report: A 30 year-old Caucasian female with no known past medical history presented to the ED with worsening sore throat, odynophagia and anterior neck pain. Symptoms began 4 weeks ago prior to presentation, 1 day after receiving an influenza vaccine. Other symptoms included loss of appetite, chills, fever, fatigue, malaise, abdominal pain, diarrhea, palpitations, heat intolerance and 5lbs weight loss. She was treated by her primary care provider for suspected pharyngitis with a course of corticosteroids and antibiotics. Two weeks later, given worsening symptoms, was referred to the emergency room. On exam, she appeared anxious and was tachycardic (124 beats per minute) and tachypneic (28 breaths per minute). She had no lid lag, stare, thyromegaly or thyroid bruit. However, there was significant tenderness on palpation of the anterior neck. Laboratory evaluation was notable for TSH <0.01 uIU/mL (0.39 - 4.0.8), free T4 5.19 ng/dL (0.58 - 1.64), free T3 10 pg/ml (2.53-3.87), ESR 95 mm/hr (0-20) and CRP 9.339 mg/dl (0.0-0.9) consistent with thyrotoxicosis. Given Burh-Wartofsky score of 45, there was a concern for impending thyroid storm. She received hydrocortisone, methimazole and beta blockers and was admitted to the intensive care unit. She responded dramatically to treatment and was discharged within 24 hours on prednisone and metoprolol. The 24-hour radioactive iodine uptake (RAIU) was 2.7% 2 weeks post admission, consistent with a diagnosis of subacute thyroiditis. TSI was negative. Family history was negative for autoimmune disease. She continued on beta blockers with a steroid taper for 8 weeks. Thyroid function tests and inflammatory markers normalized within 3 months.Conclusion:Aside from the described patient, only three other cases of thyrotoxic crisis due to subacute thyroiditis have been reported in the literature. This case underscores the importance of thoroughly investigating the etiology of severe thyrotoxcosis, given the management and prognosis varies depending on underlying cause. Thyroiditis should be considering in the differential diagnosis of thyroid storm in patients who do not have a personal or family history of autoimmunity and present with neck tenderness in the setting of a precipitating event. Subacute thyroiditis is very uncommon after influenza vaccine, there have been 4 reported cases.

SUN-560 Thyrotoxic Hashimoto's Disease: Is It Graves' Thyrotoxicosis or "Hashitoxicosis"?

Introduction: Hashimoto's Thyroiditis (HT) and Graves' Disease (GD) reflect two extremes in the spectrum of autoimmune thyroid diseases. In HT, there are anti-thyroid peroxidase antibodies thought, but not proven, to be destructive to thyroid follicles as well as thyroid stimulating hormone (TSH) stimulation-blocking antibodies which block the action of TSH and cause damage and atrophy of the thyroid gland leading to hypothyroidism. On the other hand, GD is characterized by primary hyperthyroidism due to stimulating autoantibodies against TSH receptors. While some of the patients with GD can develop spontaneous hypothyroidism due to HT, development of GD with hyperthyroidism following HT is unusual (1). We report a case of development of GD in a case of long standing HT. Case Report: A 55-year-old woman with a 20-year history of HT on stable doses of levothyroxine was found to be hyperthyroid on routine follow up. She presented with clinical signs of hyperthyroidism including weight loss of 40 pounds over 1 year and periorbital edema. The dose of levothyroxine was tapered and ultimately stopped over six months. Despite discontinuation of thyroid hormone, she continued to remain hyperthyroid. Labs were significant for elevated free T4 2.28 (0.82-1.77 ng/dL), elevated free T3 9.2, (2.0-4.4 pg/mL) and suppressed TSH, 0.006 (0.0-0.55 IU/L). Further testing revealed elevated thyroid antibodies including TSI of 10.4 (0.0-0.55 IU/L), Thyroglobulin Ab of 50.6 (0.0-0.9 IU/mL), TSH receptor Ab of 6.1 (>1.5 U/L positive) and TPO Ab of > 600 (0.0-34 IU/mL). Thyroid ultrasound disclosed an enlarged, heterogenous and hyperemic thyroid parenchyma. The 24-hour radioactive iodine uptake was elevated at 52% (8-35%) indicative of hyperthyroidism, most likely from GD. She was treated with methimazole and atenolol, followed by total thyroidectomy. Surgical pathologyrevealed diffuse chronic lymphocytic thyroiditis with lymphoid aggregates, fibrosis, adenomatous nodules with oncocytic changes and reactive nuclear atypia. Conclusion: Although development of GD following HT is rare, it can occur suggesting that HT does not always result in irreversible destruction of the thyroid gland. Patients with thyroid autoimmune disease have both thyroid hormone receptor stimulating and thyroid hormone receptor blocking antibodies and clinical manifestations depend upon the level of these antibodies and the state of the thyroid gland. Because patients with HT can transform to GD at any point due to a change of blocking to stimulating antibodies, clinicians should be aware of the potential for this transformation.

Prediction of thyroidal 131I effective half-life in patients with Graves' disease.

PurposeCalculation of effective thyroidal half-life (Teff) of iodine-131(131I) is cumbersome and tedious. The aim of this study was to investigate factors that could be used to predict Teff and to develop a Teff prediction model in Graves’ disease patients.MethodsA total of 256 patients with GD were involved in this study. We investigated the influences of age, gender, disease duration, thyroid weight, antithyroid drugs, antithyroid drugs discontinuation period (ADP), thyroid function indexes, thyroid autoantibodies, thyroid-stimulating hormone receptor antibody (TRAb) level and radioactive iodine uptake (RAIU) values before 131I therapy on Teff, applying univariate and multivariate analyses.ResultsTeff correlated negatively with thyroid peroxidase antibody, TRAb and thyroid weight, as well as positively with 24-hour, 48-hour, and 72-hour RAIU. Additionally, a longer ADP (especially≥ 14d) or without antithyroid drugs before 131I therapy led to a longer Teff. Stepwise multiple linear regression analysis showed that 24-hour and 72-hour RAIU were statistically significant predictors of Teff (P<0.001). The relationship was: predictive Teff=5.277+0.295×72-hour RAIU-0.217×24-hour RAIU (r =0.865, P < 0.001).ConclusionThe present results indicate that prediction of Teff from 24-hour and 72-hour RAIU is feasible in patients with Graves’ disease, with high prediction accuracy.

Lingual Thyroid Ectopia: Diagnostic SPECT/CT Imaging and Radioactive Iodine Treatment.

Lingual thyroid is a rare abnormality of thyroid development that is usually treated conservatively with levothyroxine replacement. Rarely, it becomes large enough to cause obstructive symptoms in the oral cavity, requiring definitive treatment. This study reports on three patients with lingual thyroid treated with radioactive iodine-131 ((131)I) with successful radioablation of their ectopic thyroid tissues. Measurement of 24-hour radioactive iodine uptake within thyroidal tissues and hybrid single-photon emission computed tomography/computed tomography imaging using either iodine-123 or technetium-99m pertechnetate scans were performed in all patients demonstrating the location and size of lingual thyroid and absence of an orthotopic thyroid gland. The aim of this study was to describe nonsurgical management of obstructive lingual thyroid tissue with (131)I therapy for lingual thyroid radioablation. Patients were prepared with a low-iodine diet and levothyroxine withdrawal prior to radioablation for optimizing (131)I uptake in ectopic thyroid tissues. Hybrid single-photon emission computed tomography/computed tomography measurement of anatomic size of lingual thyroid tissue and radioactive iodine uptake guided the selection of therapeutic doses, resulting in administration of 10.7, 17.5, and 15.4 mCi of (131)I, respectively. There were no post-therapy complications, and clinical follow-up demonstrated resolution of obstructive oropharyngeal symptoms. Ectopic lingual thyroid tissue is rarely associated with obstructive oropharyngeal symptoms due to progressive enlargement. Radioiodine therapy with (131)I is an effective treatment modality for ablation of ectopic thyroid tissue as an alternative to surgery.

The value of the mean peak systolic velocity of the superior thyroidal artery in the differential diagnosis of thyrotoxicosis.

Purpose:The aim of this study was to validate the superior thyroidal artery mean peak systolic velocity (STA-mPSV) as an alternative to other diagnostic parameters in the differentiation of the causes of thyrotoxicosis in Korean patients.Methods:This study was conducted with newly diagnosed and untreated thyrotoxic patients. Forty patients were diagnosed with Graves disease (GD) and 20 patients with destructive thyroiditis (DT). Another 60 healthy subjects without thyroid disease participated as the control group. Blood samples were taken to evaluate the thyroid function and thyroid autoantibodies (TRAb). Twenty-four hour radioactive iodine uptake (RAIU) scanning was performed to confirm GD or DT. The STA-mPSV was measured using color Doppler ultrasonography.Results:The STA-mPSV was significantly higher in the untreated GD group than in the DT group (GD, 78.96±29.04 cm/sec; DT, 29.97±14.67 cm/sec; control, 17.55±4.99 cm/sec; P<0.001). The area under the curve (AUC) of the STA-mPSV for the differential diagnosis of untreated GD and DT was 0.9506 (optimal cutoff value, 41.3 cm/sec; sensitivity, 95%, 38/40; specificity, 85%, 17/20) in the receiver operating characteristic analysis. The AUC values of the STA-mPSV, RAIU, and TRAb were 0.9506, 1, and 0.9988, respectively (P=0.159).Conclusion:In clinical practice, the STA-mPSV has a diagnostic value similar to that of the TRAb and 24-hour RAIU in the differential diagnosis of newly diagnosed Korean thyrotoxic patients.

Measuring the extent of total thyroidectomy for differentiated thyroid carcinoma using radioactive iodine imaging: relationship with serum thyroglobulin and clinical outcomes.

IMPORTANCE Despite performing total thyroidectomy (TT), postoperative radioactive iodine (RAI) imaging often demonstrates the presence of residual thyroid tissue within the operative bed. OBJECTIVE To measure the extent of TT using postoperative RAI imaging and assessing serum thyroglobulin (Tg) level for patients with differentiated thyroid carcinoma (DTC). DESIGN, SETTING, AND PARTICIPANTS We evaluated 245 patients undergoing TT for clinically staged cT1-3N0M0 DTC, who underwent diagnostic postoperative RAI imaging. INTERVENTIONS Total thyroidectomy. MAIN OUTCOMES AND MEASURES On the basis of quantitative measurements, RAI uptake (RAIU) in the thyroid bed of 0.2% of administered activity was selected as the cutpoint to determine the presence or absence of thyroid remnant. RESULTS By postoperative RAI imaging, TT in 106 patients (43%) resulted in RAIU of less than 0.2%. In the remaining 139 patients (57%), there was measurable iodine-avid thyroid tissue and/or tumor in the thyroid bed (n = 117 [84%]), the neck (n = 4 [3%]), or both (n = 18 [13%]). For the entire study population, mean 24-hour RAIU was 0.62%. Stimulated serum Tg levels were obtained in 232 of 245 patients (95%). Measurable stimulated Tg level (≥1 ng/mL) (to convert to micrograms per liter, multiply by 1) was found in 26 of 102 patients (25%) without thyroid remnant and in 87of 133 patients (65%) with thyroid remnant (P &lt; .001). CONCLUSIONS AND RELEVANCE A goal of postthyroidectomy RAIU of less than 0.2% helps maximize the likelihood of an unmeasurable postoperative Tg level, potentially simplifying follow-up evaluation and reducing the use of postoperative RAI in order to facilitate surveillance.

Recurrent Postpartum Thyroiditis in a Patient With Chronic Autoimmune Thyroiditis: A Case Report

Postpartum thyroiditis is a destructive thyroiditis induced by an autoimmune mechanism that begins within the first few months after delivery. Postpartum thyroiditis can also occur after spontaneous abortion, here we report three documented episodes of recurrent postpartum thyroiditis, one of which developed after pregnancy loss. Our patient is a 33-year-old woman who complained of discomfort with palpitations two months after her first delivery. Laboratory examination of thyroid function tests (TFT) revealed transient hyperthyroidism followed by hypothyroidism and then recovery (a classic triphasic pattern). Two years later, the patient suffered a spontaneous abortion of her second pregnancy at 16 weeks gestation. Three months after the loss of this second pregnancy, TFT showed the classic triphasic pattern again. Two years following the spontaneous abortion, the patient gave birth to her second child, and three months after delivery, the patient complained of heat intolerance and irritability. Laboratory tests during this time showed an elevated FT4 and a low TSH. Tc-99m scintigraphy showed nonvisualization of both thyroid lobes, and 24-hour radioactive iodine uptake was 0.2%. This patient in this case presented with the classic triphasic pattern in all three episodes. doi: http://dx.doi.org/10.4021/jmc1060w

Recurrent Postpartum Thyroiditis in a Patient With Chronic Autoimmune Thyroiditis: A Case Report

Postpartum thyroiditis is a destructive thyroiditis induced by an autoimmune mechanism that begins within the first few months after delivery. Postpartum thyroiditis can also occur after spontaneous abortion, here we report three documented episodes of recurrent postpartum thyroiditis, one of which developed after pregnancy loss. Our patient is a 33-year-old woman who complained of discomfort with palpitations two months after her first delivery. Laboratory examination of thyroid function tests (TFT) revealed transient hyperthyroidism followed by hypothyroidism and then recovery (a classic triphasic pattern). Two years later, the patient suffered a spontaneous abortion of her second pregnancy at 16 weeks gestation. Three months after the loss of this second pregnancy, TFT showed the classic triphasic pattern again. Two years following the spontaneous abortion, the patient gave birth to her second child, and three months after delivery, the patient complained of heat intolerance and irritability. Laboratory tests during this time showed an elevated FT4 and a low TSH. Tc-99m scintigraphy showed nonvisualization of both thyroid lobes, and 24-hour radioactive iodine uptake was 0.2%. This patient in this case presented with the classic triphasic pattern in all three episodes. J Med Cases. 2013;4(4):208-211 doi: https://doi.org/10.4021/jmc1060w

Prediction of late (24-hour) radioactive iodine uptake using early (3-hour) uptake values in Japanese patients with Graves’ disease

Measurement of 24-hour radioactive iodine uptake (RAIU), which is commonly used to calculate the dose of radioiodine (RI) therapy, cannot be accomplished in a single day. The purpose of this study was to predict 24-hour RAIU from 3-hour RAIU in Japanese patients with Graves' disease, and to investigate other factors that could be used to predict 24-hour RAIU. A total of 66 Japanese patients (14 men and 52 women; age, 17-83 years) with Graves' disease who had undergone both 3-hour and 24-hour ¹²³I RAIU measurements between January 2006 and September 2011 were included in this study. Stepwise multiple regression analyses were performed in order to identify factors that could be used to predict 24-hour RAIU. The investigated factors were gender, age, thyroid volume, TSH, free thyroxine (FT4), free triiodothyronine (FT3), serum creatinine, second generation assay TSH receptor antibody (TRAb2), antithyroid drugs discontinuation period (ADP), iodine restriction period and 3-hour RAIU. The ADP was converted to an ordinal scale ADP score (ADPS) for multiple regression analyses. Multiple regression analyses showed that 3-hour RAIU (P < 0.001), FT3 (P < 0.001) and ADPS (P < 0.001) were statistically significant predictive factors of 24-hour RAIU. The relationship between 24-hour RAIU (LU) and 3-hour RAIU (EU), FT3 and ADPS was: LU = 11.5 + 29.1 × log₁₀ EU + 23.0 × log₁₀ FT3 - 2.7 × ADPS (r = 0.82, P < 0.001). The present results indicate that prediction of LU from EU, FT3 and ADPS is feasible in Japanese patients with Graves' disease.

The Odyssey of Nontoxic Nodular Goiter (NTNG) in Greece under Suppression Therapy, and after Improvement of Iodine Deficiency

Nontoxic nodular goiter (NTNG) is common in endemic goiter regions. Thyroxine (T4) is often used to treat NTNG. There is little information regarding T4 treatment in regions that have recently become iodine sufficient. We studied the effect of T4 treatment on thyroid function tests in southwestern Greece (SWG), a recently iodine-sufficient area. We studied 827 residents of SWG (group A) to determine goiter prevalence, thyroid function, and urinary iodine concentration (UIC). Group B: 385 consecutive patients with thyroid dysfunction. Of these, 89 had NTNG and followed for 10 years on T4 treatment, and 296 had hyperthyroidism. Group C: 29 patients with NTNG, treated with triiodothyronine (T3) 50 mug/day and followed for 6 months. Measurements included serum T4 and 24-hour radioactive iodine uptake (RAIU) before and at the end of T3 administration. The median UIC in group A was 114 microg/L. In group B (89 patients), the incidence of newly diagnosed hyperthyroidism was 5-7% per year with a cumulative percentage of 33% at the 10th year. The initial thyrotropin (TSH) was lower (0.78 +/- 0.51 mIU/L) in those who developed thyrotoxicosis compared to those who remained euthyroid (1.17 +/- 0.74 mIU/L) (p < 0.05). In 296 thyrotoxic patients, the incidence of autoimmune hyperthyroidism and toxic multi-nodular goiter (TMNG) was similar. In group C, 10/29 patients remained euthyroid and the 24-hour RAIU decreased by 49% during T3 treatment. Similarly, serum T4 decreased by 49%. In the remaining patients who developed hyperthyroidism, 24-hour RAIU and T4 were decreased by 19% and 22%, respectively. In SWG, a recently iodine-sufficient region, the risk of developing hyperthyroidism in patients with NTNG after administration of 100-150 microg T4 is relatively high in those whose serum TSH before T4 treatment is in the lower normal range. Therefore, T4 treatment should be avoided in these patients.

Radioactive Iodine in the Treatment of Type-2 Amiodarone-Induced Thyrotoxicosis

Amiodarone-induced thyrotoxicosis (AIT) is usually classified into two types: type 1, in which a high iodine content triggers the autonomous production of thyroid hormone; and type 2, in which destructive thyroiditis causes the release of preformed thyroid hormone. AIT is a difficult management problem that sometimes requires ablative thyroid therapy. The use of radioactive iodine (RAI) therapy in patients with type-1 AIT who had a 24-hour radioactive iodine uptake (RAIU) value of >10% has been previously reported. Despite its documented efficacy at usual doses (10-30 mCi) in patients with type-1 AIT, the efficacy of RAI in those with type-2 AIT has never been questioned, because type-2 patients usually have low RAIU. We thought that high adjusted-dose RAI might be an attractive alternative to thyroid gland ablation in patients with type-2 AIT. Four patients with type-2 AIT who required thyroid ablation were included in the study. These individuals were either poor candidates for surgery or had refused surgery. The size of the thyroid gland in all subjects was within normal limits, and each thyroid was characterized by a homogenous echotexture on ultrasonography, the absence of vascularity on Doppler sonography, a low (<4%) 24-hour RAIU value and the absence of thyroid autoantibodies-all of which are characteristic of type-2 AIT. The patients were initially treated with thionamides and glucocorticoids. All patients except one achieved euthyroidism before RAI therapy. All four patients received one dose of RAI (range 29-80 mCi) and followed up for 12 months. No exacerbation of thyrotoxicosis was noted after RAI therapy. Hypothyroidism (in three patients) or euthyroidism (in one patient) was achieved in first six months. In patients with type-2 AIT, RAI treatment may be the therapy of choice for thyroid gland ablation.

Accuracy Considerations When Using Early (Four- or Six-Hour) Radioactive Iodine Uptake to Predict Twenty-Four-Hour Values for Radioactive Iodine Dosage in the Treatment of Graves' Disease

Although literature has offered methods to predict 24-hour radioactive iodine uptake values from early (4- to 6-hour) measurements, the resultant dosage errors have not been examined. Potential errors include underdosage, overdosage, and a failure to recognize rapid turnover patients (early-to-late uptake ratios > or = 1) who are at high risk for treatment failure and full-body radiation exposure. We developed and tested a novel method for minimizing error involved in using a single early uptake measurement to derive late uptake. From a retrospective analysis of 203 Graves' disease patients, receiver operating characteristic (ROC) curve analysis enabled us to identify patients likely to experience rapid turnover and therefore should receive 24-hour studies. Twenty-four-hour uptake measurements are necessary with 77% or more 4-hour uptake values and 80% or more 6-hour values. After eliminating these patients, we developed linear regression equations to predict the 24-hour uptake from 4-hour (n = 61) and 6-hour (n = 22) rule groups, testing their efficacy on separate 4-hour (n = 61) and 6-hour (n = 21) patient groups. We also used our test population to measure error in four early-to-late uptake conversion formulas presented in the literature. Error involved in these predictions ranged from a 10.6% overestimate for 4-hour calculations to a 5.9% underestimate for 6-hour calculations. When applied to two dosage formulas incorporating gland size, absorbed dose, and 24-hour uptake, average dosage error was 7%. In comparison to the other sources of error radioactive iodine (131I) dosimetry, potential error in predicting 24-hour uptake from 4- or 6-hour uptake values is low.

Alteration of radioactive iodine uptake after treatment of hyperthyroidism with iodine 131.

To determine whether a therapeutic dose of iodine 131 affects the results of 24-hour radioactive iodine uptake (RAIU) testing, we reviewed records of hyperthyroid patients previously treated with 131I at Michigan State University and its affiliated hospitals. We identified 26 patients who had had clinical evaluation and determination of the serum thyroxine (T4) level, triiodothyronine resin uptake (T3RU), and RAIU (using 131I) within two weeks before and several months after the therapeutic dose of 131I. Before treatment, all patients had clinical hyperthyroidism, with an elevated T4 level and increased T3RU and RAIU. After treatment with 131I, eight patients (31%) had an RAIU that was discordant with their clinical and biochemical (T4 and T3RU) assessment. In six patients (23%) of the RAIU was inappropriately high, and in two patients (8%) it was inappropriately low. Since we did not identify any other factors known to interfere with the results of RAIU testing, we conclude that a therapeutic dose of 131I, may by itself increase or decrease a subsequent RAIU determination; therefore, after treatment with 131I, RAIU is not a good diagnostic index of thyroid activity.

MR imaging in thyroid disorders: correlation of signal intensity with Graves disease activity.

Thirty-six patients with a variety of thyroid disorders and eight healthy subjects were studied with T1- and T2-weighted magnetic resonance (MR) imaging. Solid benign nodules, malignant tumors, and inflammatory conditions were not distinguishable by thyroidal MR signal intensity, but almost all patients with Graves disease had a moderate to marked diffuse increase in signal intensity at both settings. Quantitative evaluation showed that in these patients, the thyroid-muscle signal intensity contrast ratio was linearly related to both the serum thyroxine (T4) level and the 24-hour radioactive iodine uptake. In three patients treated with iodine 131, this contrast ratio rose or fell in parallel with the serum T4 level and 24-hour radioactive iodine uptake. Either parenchymal changes or increased vascularity in Graves disease, or both, could produce these findings. In patients without Graves disease, signal intensity was not correlated with serum T4 levels. These findings suggest that MR signal intensity may reflect the activity of the stimulatory process in Graves disease and may therefore be a useful measure of thyroid function in this disorder, with both diagnostic and prognostic value.

Treating Lymphocytic Thyroiditis With Spontaneously Resolving Hyperthyroidism-Reply

In Reply. —Dr Compagno's criticism of our editorial is somewhat valid. Clearly, only when a tissue diagnosis is established, can one be absolutely certain that the diagnosis is lymphocytic thyroiditis with SRH. It is also true that a fine needle aspiration of the thyroid is a relatively innocuous procedure. However, several comments need to be made to defend our statement. First, most internists are not well-versed in doing thyroid biopsies and most pathologists cannot readily interpret the fine needle-aspiration cytologic specimens. Second, there are patients with SRH who are not seen with a goiter and, therefore, would not be ideal candidates for thyroid biopsy. Moreover, the most valid reason for not routinely doing thyroid biopsies is that the diagnosis can readily be established on clinical grounds. 1 Only in unusual circumstances, when one cannot accomplish a 24-hour radioactive iodine uptake, should a thyroid biopsy be considered. Such a circumstance would

Postpartum thyrotoxicosis in a patient with Graves' disease. Association with low radioactive iodine uptake

A patient with previously diagnosed Graves' hyperthyroidism had a transient episode of thyrotoxicosis three months postpartum. This was associated with a diffusely enlarged thyroid gland, a rise in antithyroid microsomal antibody titer, a 24-hour radioactive iodine uptake (RAIU) of 1%, and an aspiration biopsy specimen suggestive of chronic lymphocytic thyroiditis. An alternative cause for the depressed RAIU was not discovered. This case would suggest that patients with previously diagnosed Graves' disease can have thyrotoxicosis without an enhanced RAIU and that the postpartum thyrotoxic syndrome may involve an immunologic injury causing a release of preformed thyroid hormone. (<i>JAMA</i>243:1454-1456, 1980)

Postpartum Thyrotoxicosis in a Patient With Graves' Disease

A patient with previously diagnosed Graves' hyperthyroidism had a transient episode of thyrotoxicosis three months postpartum. This was associated with a diffusely enlarged thyroid gland, a rise in antithyroid microsomal antibody titer, a 24-hour radioactive iodine uptake (RAIU) of 1%, and an aspiration biopsy specimen suggestive of chronic lymphocytic thyroiditis. An alternative cause for the depressed RAIU was not discovered. This case would suggest that patients with previously diagnosed Graves' disease can have thyrotoxicosis without an enhanced RAIU and that the postpartum thyrotoxic syndrome may involve an immunologic injury causing a release of performed thyroid hormone.