Radioactive Iodine Scan Research Articles

8105 Radiation-Induced Hyperthyroidism in the Context of Palliative Radiation Therapy

Abstract Disclosure: A. Randhawa: None. G. Palaguachi: None. J.G. Karam: None. Introduction: Palliative radiotherapy, designed to alleviate focal symptoms in advanced, incurable cancer, aims to enhance quality of life with minimal treatment burden. The thyroid gland's susceptibility to neck radiation is known, primarily leading to hypothyroidism. However, hyperthyroidism is a much less frequently reported adverse effect that is poorly understood. This case report highlights an unusual instance of radiation-induced hyperthyroidism. Case Presentation:The patient is a 53 years-old woman with history of Ewing’s sarcoma of the sacrum diagnosed in August 2022, treated initially with chemotherapy (cyclophosphamide, vincristine, etoposide and ifosfamide), but diagnosed with leptomeningeal metastasis and T12/L1 mass in October 2023 when she presented with lower extremities weakness and urinary incontinence. She underwent T12-L1 laminectomy, resection of tumor and fusion, and was started on palliative intent radiation therapy for the brain and C-spine. A month later, she was admitted for altered mental status and was found to be persistently tachycardic at 140 bpm. Thyroid function testing was sent and revealed hyperthyroidism with TSH of 0.07 mIU/L (0.39-4.08), Free T4 of 1.74 ng/dl (0.58-1.64), T4 of 10.7ug/ml (4.4-9.5), T3 of 0.54 ng/ml (0.72-1.35), with undetectable Thyroid Peroxidase Antibodies and Thyroid Stimulating Immunoglobulin level. Thyroid Ultrasound showed a small and homogenous thyroid gland with no discrete nodules. Radioactive Iodine uptake and scan was not obtained because of exposure to iodized contrast during hospital stay. The patient had no available baseline thyroid function tests. She had no recent fever or viral illness. Unfortunately, her clinical condition deteriorated rapidly, and she passed away on the seventh day of admission. Conclusion: While hypothyroidism is a well-established consequence of high-dose irradiation, the mechanisms behind the rarer radiation-induced hyperthyroidism remain unclear. Speculation includes the release of autoantigens from damaged thyroid glands, triggering an immune response and potentially leading to Graves' hyperthyroidism. However, our case more likely represents a hyperthyroid phase in the triphasic sequence of destructive subacute thyroiditis, given the absence of elevated thyroid antibodies, thyroid nodules, and other causes of thyroiditis. Increasing awareness of radiation-induced hyperthyroidism, unraveling its mechanisms, and refining diagnostic strategies such as obtaining baseline and monitoring thyroid function testing are crucial, particularly in the context of palliative therapy, where striking the delicate balance between efficacy and minimizing toxicity is paramount. Presentation: 6/3/2024

8465 Diagnostic Conundrum: The Mystery of Metastatic Papillary Thyroid Cancer with Persistently Elusive Thyroglobulin

Abstract Disclosure: P. Vemparala: None. M. Bollineni: None. Introduction- Among endocrine malignancies, differentiated thyroid cancers account for the majority with most of them boasting a favorable prognosis. Thyroglobulin, a pivotal biochemical marker, aids in detecting recurrence or persistent disease when combined with neck ultrasound, I-131 scintigraphy, and FDG PET scans. Anti-thyroglobulin antibodies, found in a quarter of cases, can falsely lower serum thyroglobulin levels in immunometric assays. Our intriguing case features a patient with metastatic papillary thyroid cancer, yet thyroglobulin levels persistently eluded detection. CASE PRESENTATION- A 33-year-old female presented initially to an outside facility with neck swelling, leading to a diagnosis of a 4 x 3 cm papillary thyroid cancer (PTC) in the right lobe and a 0.5 x 0.5 cm focus of PTC in the left lobe, accompanied by capsular extension, malignant cells in the left lobe margin, and lymphovascular invasion. After total thyroidectomy and lymph node exploration, radioactive iodine scan detected disease in right-sided lymph nodes, treated subsequently with radioactive iodine ablation. Two years later, she presented to our clinic with neck swelling, voice changes, and fatigue. Thyroglobulin level was measured which returned at <0.1 ng/ml, however thyroglobulin antibodies were elevated at 292 IU/ml, albeit decreased from a value of 431.5 IU/ml at initial diagnosis. Elevated thyroglobulin antibodies complicated interpretation, prompting liquid chromatography-mass spectrometry (LC-MS) for accurate measurement of thyroglobulin, which returned at <0.5 ng/ml. Ultrasound indicated metastatic disease in right cervical lymph nodes, confirmed by fine needle aspiration. In-office ultrasound-guided FNA of additional nodes validated metastasis. Modified radical neck dissection revealed metastatic PTC in 7 out of 34 lymph nodes. Surprisingly, thyroglobulin levels remained <0.5 ng/ml, pre- and post-operatively. Referred for radioactive iodine ablation, her complex journey underscored the challenges in monitoring thyroid cancer recurrence or persistent disease with thyroglobulin levels even by methods such as mass spectrometry. Conclusion- Key learnings from this case highlight the importance of cognizance in utilizing thyroglobulin levels to guide adjuvant therapy decisions and for postoperative monitoring in high risk patients, as low levels do not rule out recurrence or persistence. Anti-thyroglobulin antibodies pose challenges, necessitating techniques like LC-MS. Finally, recognizing “nonsecretor” thyroid cancers, an aggressive subgroup with poorer prognosis, is vital as they often present with low or undetectable thyroglobulin levels. Presentation: 6/2/2024

Chapter 6: Risk Stratification and Surveillance in Differentiated Thyroid Cancers

ABSTRACT Surveillance strategies in differentiated thyroid cancers (DTCs) differ from other head-and-neck subsites by virtue of their excellent prognosis. Guidelines in this chapter are based on a comprehensive literature review, particularly in the Indian setting concurred upon by experts in the field. Key recommendations include serial measurement of thyroglobulin values, thyroglobulin antibodies, and risk-based suppression of thyroid-stimulating hormone during follow-up of treated DTCs, with radioactive iodine scan and structural imaging based on dynamic risk stratification. These recommendations take into consideration prevailing Indian scenario related to reliability of follow-up, insurance coverage, as well as burden on health-care systems.

FRI504 Ectopic Hyperactive Mediastinal Thyroid Tissue: A Case Report

Abstract Disclosure: C. Dimech: None. G. Jaiswal: None. A. Bhargava: None. Ectopic thyroid tissue is usually located along the normal path of the caudal migration of thyroid tissue during embryonic life. Substernal goiters are thought to occur by either the enlargement of ectopic mediastinal thyroid tissue (primary mediastinal goiter) or abnormal extension of thyroid issue into the superior mediastinum (secondary mediastinal goiter). Typically these goiters remain asymptomatic, and rarely result in hyperthyroidism or local compression of the surrounding area. We report a case of an 89-year-old Caucasian female with history of a multinodular goiter status post right hemithyroidectomy, who initially presented for subclinical hyperthyroidism. Further evaluation revealed negative thyroid stimulating antibodies. A thyroid ultrasound demonstrated a surgically absent right lobe, with a small heterogenous left lobe. A nuclear medicine radioactive iodine uptake and scan showed hypermetabolic residual thyroid tissue with a large area of increased radiotracer uptake projecting over the right anterior chest, concerning for ectopic thyroid tissue. A subsequent chest CT without contrast revealed an approximately 5 centimeter partially calcified anterior mediastinal/retrosternal mass. Given the patient’s age and co-morbidities, a decision was made to treat the hyperthyroidism with methimazole and monitor the ectopic tissue for worsening symptoms of compression. In cases with severe compressive symptoms, or difficult to treat hyperthyroidism, a surgical option must be considered. Presentation: Friday, June 16, 2023

SAT530 Use of Tamoxifen and Cabergoline to Suppress Breast Tissue Uptake of Radioactive Iodine Among Differentiated Thyroid Cancer Patients

Abstract Disclosure: A.H. Mohamed: None. M. Basina: None. Background: Radioactive iodine (RAI) has been used in thyroid cancer treatment. Physiologic breast tissue uptake and accumulation of RAI are not desirable due to increased carcinogenesis risk. Case1:31 years old non lactating female diagnosed with stage IVB papillary thyroid cancer and underwent total thyroidectomy and bilateral neck dissection. She had high initial risk with stage of T3N1bM1 and underwent 118 mCi of I-131 treatment with pulmonary foci. One year later, she had biochemical and structural incomplete response and underwent I-123 RAI uptake scan demonstrating residual disease in the right neck and diffuse breast uptake, thus, I-131 treatment was deferred. The patient was started on cabergoline 0.5 mg daily for 2 months. Repeated I-123 uptake scan during day 2 of Cabergoline remained with diffuse breast uptake. Four months later, another repeated RAI uptake scan after 4 months showed minimal breast uptake and RAI I-131 treatment was given. She had normal mammogram screening. Case2: 41 years old non lactating female diagnosed with stage II papillary thyroid cancer and underwent total thyroidectomy with right neck dissection. She had moderate initial risk with stage of T3 N1aM0 and underwent 159 mCI of I-131 treatment. Two years later, she had structural incomplete response and repeated I-123 uptake scan showed thyroid bed foci of avid uptake and diffuse bilateral breast uptake, thus, I-131 therapy was deferred. The patient was started on cabergoline 0.25 mg daily for 4 weeks and Tamoxifen 10 mg twice daily for 10 days prior to repeated I-123 RAI scan that redemonstrated thyroid bed foci without breast tissue uptake. She had normal mammogram screening. DiscussionPotential malignancy risk secondary to non-thyroidal RAI accumulation in tissues was reported. The mechanism of breast RAI uptake involves Na/iodide symporter channel regulated by prolactin and estrogen. Blocking the effect of these hormones prior to I-131 administration are believed to prevent breast uptake. We describe two papillary thyroid cancer cases with breast RAI uptake that was suppressed partially with Cabergoline (prolactin lowering agent) and fully with combination of Cabergoline and Tamoxifen (estrogen receptor blocker). Further studies are needed to evaluate the efficacy of Tamoxifen and cabergoline in suppressing physiologic breast RAI uptake. Presentation Date: Saturday, June 17, 2023

Establishing a Cutoff Serum Thyroglobulin Value for the Diagnosis and Management of Well-Differentiated Thyroid Cancer.

Objective The aim of this study was to define a cutoff serum thyroglobulin (Tg) level associated with either residual or metastasis that may help decide postoperative radioactive iodine (RAI) scan and treatment in differentiated thyroid cancer (DTC) patients residing in low-income countries like Nepal. Methods We prospectively studied a total of 81 patients (female-to-male ratio of 3.0:1; mean age: 37.3 ± 14.0 years, within age range of 14-88 years) who underwent total thyroidectomy with/without neck dissection and were referred for RAI whole-body scan (WBS) ± RAI ablation or adjuvant treatment in the department of Nuclear Medicine, Chitwan Medical College. We calculated the cutoff value of Tg using receiver operating characteristic (ROC) curve analysis. Results Forty-six of 81 patients (56.7%) had remnants in the thyroid bed, 26/81 (32.1%) had regional lymph node metastasis, 9/81 (11.1%) had distant lymph node metastasis, 3/81 (3.7%) had lung metastases, and only 1/81 (1.2%) had bone metastases. RAI WBS was positive in 61/81 (75.3%) patients and negative in 20/81 (24.7%) patients. Seventeen of 81 (20.9%) patients had negative RAI scans with low serum Tg levels; only 3/81 (3.7%) patients had Tg elevated negative RAI scan (TENIS). Although scan was positive in 61/81 (75.3%) patients, 64/81 (79.0%) patients received treatment with RAI, of which 3/81 (3.7%) patients were TENIS patients. There was a significant difference in serum Tg levels between patients who received or did not receive RAI ablation or treatment ( p < 0.05). On ROC curve analysis, the cutoff value of Tg levels between patients who received and did not receive treatment was 2.9 ng/mL (sensitivity: 85.9%; specificity: 94.1%; positive predictive value [PPV], 98.2%; negative predictive value [NPV]: 64.0%; AUC: 0.938). Conclusion We identified a cutoff value of 2.9 ng/mL between patients who required or did not require treatment with high sensitivity, specificity, and PPVs.

Incidentally Detected 131-Iodine Avid Parotid Oncocytoma Coexistent with Papillary Carcinoma Thyroid.

131-I radioactive iodine (RAI) scan is an important modality in the management of differentiated thyroid cancer to detect recurrent or residual disease. Thus it is important to have knowledge about the possibility of false positive findings in these scans to avoid wrongful diagnosis and unnecessary treatment. We here by present a patient who underwent total thyroidectomy with lymph node dissection and followed by radioactive iodine therapy for papillary thyroid cancer. He had 131-I iodine avid nodular lesion in the left parotid gland which was later proven to be oncocytoma on histopathology. False positive findings on radioactive iodine scans are a possibility which should be known to surgeons as well as nuclear medicine physicians for accurate diagnosis and appropriate management.

Abstract #1408165: An Atypical Case of Subacute Thyroiditis Presenting as a Toxic Adenoma

Subacute thyroiditis is inflammation of the thyroid gland often occurring after a viral infection of the upper respiratory tract. It is an uncommon condition mostly seen in women compared to men and is characterized by neck pain, a tender thyroid on exam with hyperthyroidism on initial presentation and low uptake on radioiodine imaging. A 36-year-old American Indian female with no significant past medical history was referred to Endocrinology for a new diagnosis of hyperthyroidism and for fine needle aspiration of thyroid nodules. Four months prior the patient was experiencing intermittent palpitations along with right sided neck pain. A thyroid ultrasound ordered by her primary care provider showed multiple nodules, including a 1.9 cm heterogeneous nodule with eccentric calcifications in the left lower lobe (TI-RADS 4) and a 2.7 cm right hypoechoic solid nodule with ill-defined borders, taller than wide (TI-RADS 5). Her thyroid function tests revealed a TSH < 0.025 uIU/mL (nl 0.450-4.50 uIU/mL), FT4 2.64 ng/dL (nl 0.82-1.7 ng/dL), FT3 6.4 pg/mL (nl 2.0-4.4 pg/mL) and thyroglobulin antibody < 1.0 IU/ml. A radioactive iodine uptake and scan showed decreased 24-hour uptake with a single hyperfunctioning nodule in the left thyroid lobe. The patient was started on methimazole 10 mg daily which was titrated down to 5 mg daily with normalization of her thyroid function after 3 months of treatment. Repeat thyroid function at the time of her endocrine clinic visit 1 month later revealed hypothyroidism. We performed a bedside ultrasound which did not show any thyroid nodules and the biopsy was cancelled. These findings were supported by a formal thyroid ultrasound a few weeks later. Methimazole was stopped and thyroid function normalized. Further history revealed the patient was experiencing symptoms of an upper respiratory tract infection a few weeks prior to the start of the palpations and neck pain. Six months after initial presentation, thyroid function has remained normal off methimazole. This is a rare case of subacute thyroiditis with initial findings of a toxic adenoma. To our knowledge there is only one other reported case of this unusual presentation of subacute thyroiditis with focal radioiodine uptake and thyroid nodules that later resolved on repeat imaging. This case should raise awareness for other providers to consider subacute thyroiditis when evaluating patients presenting with hyperthyroidism and atypical imaging findings. The history and clinical presentation were key in making the clinical diagnosis.

Nuclear Imaging in Patients with Differentiated Thyroid Cancer and Negative Radioactive Io-dine Scan

Nuclear Imaging in Patients with Differentiated Thyroid Cancer and Negative Radioactive Io-dine Scan

Rare sites of metastases in patients with differentiated thyroid carcinoma and added value of SPECT/CT over planar whole body radioactive iodine scan

BackgroundBeing aware of the unusual or rare location of thyroid metastases helps in early diagnosis and proper patient management. Rare metastases (RM) can be missed resulting in diagnostic pitfalls and delayed treatment. The use of single-photon emission computed tomography/computed tomography (SPECT/CT) imaging in the follow-up of differentiated thyroid cancer (DTC) patients provides precise anatomical localization and characterization of RM that may be missed or misinterpreted in planar whole body iodine-131 (WBI) scan. There is a lack of knowledge about dealing with such patients, the treatment they should receive, and therapy response due to the rarity of such cases. In this work, we reported these rare cases increasing awareness about them and their methods of treatment with response to therapy and evaluated the added value of SPECT/CT imaging in changing patients’ management.Materials and methodsIn this study we reviewed all patients with DTC referred to our unit either for initial radioactive iodine-131 therapy (RAIT) or under follow-up from January 2019 to January 2022. When a suspected lesion was detected in a conventional planar WBI scan whether follow-up scan or post-therapeutic scan, SPECT/CT was acquired immediately in the same session for that region. Additional imaging modalities were performed for confirmation. Response to the given treatment either disease progression (DP) or favorable response which include complete response (CR), partial regression (PR) and stable disease (SD) recorded for each patient.ResultsTwo hundred and forty patients with DTC referred to our unit over a three-year period (from January 2019 to January 2022) were reviewed. Forty patients developed lung and bone distant metastases. Twenty-one patients were thought to have metastases at unusual sites. Due to incomplete data (no SPECT/CT pictures or confirmatory imaging), 6/21 patients were eliminated. We studied 15 patients with RM (9 females, 6 males) with a median age of 52 years (range 27–79). All patients received the initial RAIT after thyroidectomy in addition to other therapeutic modalities, e.g., radiotherapy (RTH), chemotherapy (CTH) or surgical tumor excision after detection of RM. Ten out of 15 patients (66.67%) showed favorable response to therapy (2 patients had CR, 6 patients had PR and 2 patients had SD), whereas only 5 patients had DP. Additional SPECT/CT changed management in 10/15 patients (66, 67%) of patients.ConclusionRM identification is mandatory to avoid misdiagnosis and delayed therapy. Increasing the awareness about such rare cases allows for better management. SPECT/CT could significantly impact patients' management through its precise anatomic localization and lesion characterization.

ODP463 Assess the Usefulness of Pre–Ablation Diagnostic I-123 Iodine Scans in Patients with Differentiated Thyroid Cancer

Abstract Context: Over the last decade, there have been significant changes in the post-operative management of Differentiated Thyroid cancer. The use of Diagnostic 123-Iodine scans has become controversial as many endocrinology practices now give empiric doses of RAI (Radioactive Iodine) when needed based on risk stratification. Allegheny Health Network (AHN) routinely uses I-123 Pre RAI scans prior to ablative or adjuvant therapy. As per the 2015 ATA (American Thyroid Association) guidelines – Pre therapy scans and/or measurement of thyroid bed uptake may be useful when the extent of the thyroid remnant cannot be accurately ascertained from the surgical report or neck ultrasonography, or when the results would alter either the decision to treat or alter the activity of RAI dose that is administered. ATA recommendation is vague and further studies are needed to identify these patients who need pretreatment scan. Objective The objective of our study is to evaluate the utility of pre-therapy diagnostic 131-I scan for the risk stratification and Radioactive Iodine administration decisions in patients with Differential Thyroid cancer after thyroidectomy. Design: The study is a retrospective blinded chart review of cases at AHN. Setting: The study was conducted at an academic tertiary care center of a large Health Network in Western Pennsylvania. Method: Retrospective chart review of patients at AHN who underwent RAI treatment from 2016-2021 has been completed. 195 patients with Differentiated Thyroid cancer have been included in this study. These patients had a pre-therapy WBI (Whole Body Iodine) scan as per AHN's current clinical practice. Data collection includes demographic information, surgical details including lymph neck dissection performed or not, tumor histopathology, TNM classification, post thyroidectomy labs including TSH (Thyroid Stimulating Hormone), TG (Thyroglobulin) and TGA (Thyroglobulin antibody), pre and post-operative ultrasound, RAI dose, Pre-therapy scan findings and Post therapy RAI scan findings. Intervention: Using clinical and histopathology information a group of blinded endocrinologist are performing risk stratification to determine postoperative management with respect to radioiodine therapy (RAI) planning. The decision to withhold or to administer RAI, and the recommended low, medium or high 123-I activity will be decided by them without having information from the Diagnostic 123-Iodine scans. Main Outcome Measure: Main outcome measures will be difference in risk stratification and management with and without Diagnostic 123-Iodine scans. We plan to compare this empiric management strategy to the actual management strategy that took place based on the Pre-therapy scan. Results This will include percentage of patients where decision to treat or dose of radioactive iodine was different, when information from Diagnostic 123-Iodine scan was not available. This will help streamline Endocrinologist practice for patients with Differentiated Thyroid cancer. Presentation: No date and time listed

PSAT327 Can Cannabis Use Lead to Central Hypothyroidism

Abstract Background Marijuana has been legalized for medical use in 36 states and for recreational use in 18 states. Its effects on thyroid function and hypothalamic-pituitary-thyroid axis in humans is not known. Clinical Case 72 years old male presented to his primary care physician with occasional difficulty swallowing. He reported fatigue for 4-5 years, trouble falling asleep for 2 months, weight gain 8 pounds over last few weeks, occasional diarrhea, and intermittent episodes of heat intolerance. His past medical history included controlled type 2 diabetes mellitus, recurrent herpes simplex infection, arthritis of hip joints, short-term memory loss, anemia, carpal tunnel syndrome and benign prostatic hyperplasia. Medications included glimepiride, lisinopril, acyclovir, tamsulosin, finasteride, escitalopram. He had been smoking marijuana regularly since he was a teenager. He denied using any other supplements. His physical exam was normal with stable vital signs and normal BMI. His labs showed a low TSH (0.096 mcIU/mL, n: 0.358-3.8 mcIU/mL), normal free T4 (0.90 ng/dL, n: 0.76-1.46 ng/dL), normal total T3 (70 ng/dL, n: 60-180 ng/dL). Review of his labs showed low TSH for last 4 years progressively getting worse with normal free T4 levels. TSH-receptor antibody and TPO Antibody level were negative. His white cell count, hemoglobin and platelets were normal. His electrolytes, kidney function and liver function tests were also normal. Thyroid Ultrasound showed 2 small sub-centimeter hypoechoic nodules in the left thyroid lobe. Two years ago, a radioactive Iodine scan showed normal iodine uptake. A recent radioactive iodine uptake scan showed generalized decreased iodine uptake with no evidence of graves’ disease or toxic multinodular goiter. Conclusion Currently there are no controlled studies on the effect of marijuana use on thyroid function in humans. A cross-sectional analysis using National Health and Nutrition Examination Survey (NHANES) from 2007 to 2012 showed recent marijuana use was significantly associated with lower levels of TSH but was not associated with thyroid dysfunction (1). This study suggests that marijuana use is associated with low TSH levels. This could be due to hypothalamic suppression of TSH or may indicate a protective role against hypothyroidism. Older studies in rodents showed that cannabis exposure may lead to suppression of TSH and hypothalamic function (2). The data related to human subjects is scarce. Therefore, pathophysiologic mechanisms are speculative, although animal data support potential mechanism of hypothalamic suppression.

Diagnostic Utility of a New Assay for Thyroid Stimulating Immunoglobulins in Graves' Disease and Thyroid Eye Disease.

Background: The syndrome of thyrotoxicosis typically relies on radioactive iodine scans for establishing its etiology. Alternatively, the determination of thyrotropin (TSH) receptor antibodies (TRAbs) helps to distinguish Graves' disease (GD) from thyrotoxic thyroiditis. Current assays are impacted by limitations in sensitivity and/or turnaround time. Therefore, we decided to test a new assay for the detection of TSH receptor stimulating antibodies (TSAbs) and compare it with the clinically available assays. Methods: We enrolled 110 individuals in 5 cohorts: patients with incident or recurrent GD (cohort 1); patients with thyroiditis, painless or subacute (cohort 2); patients with Graves' orbitopathy/thyroid eye disease (TED) in cohort 3; patients with Hashimoto's thyroiditis (cohort 4), and a control group of normal volunteers (cohort 5). The patients were tested with the two clinically available assays: Roche Elecsys anti-TSHR assay (ROC-TBII) from Roche Diagnostics and Thyretain™ TSI Reporter BioAssay Kit (QUI-TSI) from Quidel. In addition, the samples were tested with the aequorin TSAb assay (OTS-TSI) provided by Otsuka Pharmaceutical Co., Ltd. (Tokyo, Japan). The data were collected in a cross-sectional manner before initiation of therapy. Results: We had 36 cases of GD, 17 cases of thyroiditis, 27 cases of TED, 10 cases of Hashimoto's thyroiditis, and 20 normal volunteers. OTS-TSI had 100% sensitivity and specificity in distinguishing GD from thyroiditis, identical with QUI-TSI but superior to ROC-TBII (sensitivity 86% and specificity 94.1%). OTS-TSI had 93% sensitivity and 100% specificity for the diagnosis of TED, compared with normal controls. QUI-TSI and ROC-TBII performed similarly in this analysis, demonstrating 82% sensitivity and 100% specificity. The range of detectable values for OTS-TSI was 20-29,000 mIU/L and the turnaround time was ≤6 hours, without the need for cell culture equipment. Conclusions: OTS-TSI performed excellently, though similarly to QUI-TSI, for the differential diagnosis of GD vs. thyroiditis, while being superior in that respect to ROC-TBII. Furthermore, OTS-TSI has superior sensitivity to QUI-TSI and ROC-TBII for TED diagnosis, while retaining high specificity. It has a short turnaround time and avoids the need for cell culture and sterility. Larger studies in U.S. populations are needed for its validation.

Effect of TSH stimulation protocols on adequacy of low-iodine diet for radioiodine administration.

Low-iodine diet (LID) is a crucial preparation for radioactive iodine (RAI) treatment or scan in thyroid cancer. The aim of this study is to analyze the influence of thyroid stimulating hormone (TSH) stimulation protocols and other clinical factors on LID adequacy. Thyroid cancer patients who underwent LID for RAI scan or treatment were retrospectively analyzed. Patients were guided to have LID for 2 weeks before RAI administration and urine iodine/creatinine ratio (UICR, μg/g Cr) was measured. TSH stimulation was conducted using either thyroid hormone withdrawal (THW) or recombinant human TSH (rhTSH) injection. Adequacy of LID was classified by UICR as 'excellent (< 50)', 'adequate (50-100)', 'inadequate (101-250)' and 'poor (> 250)'. A total of 1715 UICR measurements from 1054 patients were analyzed. UICR was significantly higher in case of rhTSH use than THW (72.4 ± 48.1 vs. 29.9 ± 45.8 μg/g Cr, P < 0.001). In patients who underwent LID twice using both TSH stimulation protocols alternately, UICR was higher in case of rhTSH than THW regardless of the order of method. Among clinical factors, female, old-age, and the first LID were significant factors to show higher UICR. Although the adequacy of LID was 'adequate' or 'excellent' in most patients, multivariate analysis demonstrated that THW method, male, young age, and prior LID-experience were significant determinants for achieving 'excellent' adequacy of LID. In conclusion, UICR was higher and the proportion of 'excellent' LID adequacy was lower with rhTSH than with THW. UICR was higher also in women, old-age, and LID-naïve patients. Further researches are required to suggest effective methods to reduce body iodine pool in case of rhTSH use and to validate the efficacy of such methods on outcomes of RAI treatment.

Comparing surgical thoroughness and recurrence in thyroid cancer patients across race/ethnicity

BackgroundFor patients with differentiated thyroid cancer who will receive postoperative radioactive iodine, thyroid remnant uptake can be calculated and may point to the thoroughness of the surgical resection. In the United States, outcome disparities exist among ethnic/racial minorities with differentiated thyroid cancer. Data about surgical thoroughness and recurrence rates across races/ethnicities do not exist. This study compared the amount of thyroid remnant uptake and cancer recurrence rates across race/ethnicity. MethodsThis was a retrospective analysis of adult patients with differentiated thyroid cancer who had postoperative radioactive iodine in 2017 and 2018 and were followed to 2020. We collected thyroid bed remnant uptake from postoperative radioactive iodine scans and analyzed it as a ratio of percent of uptake to dose of radioactive iodine received to control for varying radioactive iodine doses. Thyroid remnant, uptake to dose of radioactive iodine received, and recurrence were evaluated across race/ethnicity. ResultsOf 218 patients: 61% were White, 21% Black, 11% Asian, and 7% Hispanic; 72% were female. Seventy-one percent of patients had their surgery done by a high-volume surgeon, although volume data were not available for all. In White, Black, Asian, and Hispanic patients, median uptake was 0.68%, 0.44%, 1.5%, and 0.8%, respectively (P = .13). We did not observe differences in median uptake to dose of radioactive iodine received across groups (P = .41). Recurrence rate was 17.0% among White patients, 16.7% among Black patients, 17.6% among Asian patients, and 16.7% among Hispanic patients (P = 1.00). ConclusionWe did not observe differences across race/ethnicity in surgical thoroughness or rate of recurrence. These findings suggest that disparities may be mitigated when ethnic/racial minorities have similar access to quality surgical care.

Iatrogenic Hyperthyroidism With Recurrent Functioning Thyroid Tissue 40 Years After Thyroidectomy for Graves’ Disease

Background: Graves’ disease is an immune-mediated cause of thyrotoxicosis treated with anti-thyroid drugs (ADTs), radioactive iodine (RAI) or thyroidectomy. Thyroidectomy has been documented to have the lowest rate of recurrence amongst treatment options1. Data regarding long-term recurrence rates is limited beyond 54 months.Clinical Case: An asymptomatic 59 year old female was found to have recurrent thyrotoxicosis on routine laboratory testing. The patient underwent thyroidectomy at age 19 years for Graves’ disease. Prior records unavailable to clarify initial surgical intervention. The patient had post-surgical hypothyroidism which was managed with levothyroxine 100mcg once daily for over 20 years. A biochemically euthyroid state was clearly documented on prior laboratory testing. Initial laboratory testing with TSH <0.01mIU/L (0.45-4.50), FT3 2.8ng/dL (0.8-1.7). Levothyroxine was discontinued with persistent thyrotoxicosis after 8 weeks: TSH <0.01, FT3 5.7, FT4 1.74. Radioactive Iodine Uptake and scan was obtained after administration of 6uCi of iodine-131 which demonstrated 50.8% uptake of radioactive iodine at 24 hours (Normal 10-30%). The left thyroid gland was noted to be in normal position and enlarged with diffuse increase intensity of radiotracer uptake. The right thyroid gland was surgically absent. The patient subsequently underwent completion thyroidectomy with endocrine surgery with resolution of hyperthyroid state. Surgical pathology was benign and consistent with Graves’ disease and multinodular goiter. The patient did become hypothyroid post-operatively and required levothyroxine replacement. She is clinically and biochemically euthyroid on levothyroxine 100mcg once daily 14 months post-operatively.Conclusion: This is a case of recurrent hyperthyroidism approximately 40 years after definitive treatment with thyroidectomy. Although it is unclear whether patient underwent total thyroidectomy or subtotal thyroidectomy for initial intervention, the recurrence of thyrotoxicosis after such a long period of time has not previously been reported in the literature to the knowledge of this writer. This has important implications regarding the underlying pathophysiology of Graves’ disease and the ability of remnant thyroid tissue to regenerate over time. This also has important implications for long-term monitoring in patients with history of thyroidectomy for Graves’ disease.Reference: 1. Sundaresh, V., Brito, J. P., Wang, Z., Prokop, L. J., Stan, M. N., Murad, M. H., & Bahn, R. S. (2013). Comparative effectiveness of therapies for Graves’ hyperthyroidism: a systematic review and network meta-analysis. The Journal of clinical endocrinology and metabolism, 98(9), 3671–3677.

Postpartum Thyroid Abnormalities and Systemic Lupus Erythematosus: Is There a Link?

Abstract Introduction: Postpartum Thyroiditis (PPT) is an autoimmune disorder characterized by destruction of the thyroid gland within the first year after delivery. Systemic Lupus Erythematosus (SLE), another autoimmune disease, has been associated with a spectrum of thyroid disorders. While the prevalence of thyroid diseases in patients with SLE is increased, the association between SLE and PPT is not well known. The infrequency of encountering SLE and PPT makes abnormal thyroid tests in the postpartum period a diagnostic challenge. Clinical Case: A 27-year-old G1P1001 who was five months postpartum and not breast feeding was referred to Endocrinology clinic for evaluation of abnormal thyroid function tests. Past medical history was significant for SLE with renal and pericardial involvement. SLE was well controlled, treated with hydroxychloroquine. Family history was significant for hypothyroidism in her mother. She was asymptomatic and appeared clinically euthyroid. Vitals were stable and physical exam was negative for goiter, nodule or orbitopathy. Lab results at two months postpartum showed an elevated TSH of 3.87 UIU/mL (Normal 0.40-3.8 UIU/mL) and at four months postpartum TSH was low at 0.012 UIU/mL. Repeat labs at five months postpartum continued to show a low TSH at 0.007 UIU/mL with mildly elevated Free T4 at 1.7 ng/dL (Normal 0.6-1.6 ng/dL) and elevated Free T3 of 6.0 pg/mL (Normal 2.1-3.8 pg/mL). Anti-thyroid peroxidase antibodies (TPO), thyroid stimulating antibodies (TSI) and TSH receptor antibodies (TRAb) were negative. Thyroid Ultrasound with Doppler was within normal limits. Radioactive Iodine Uptake and Scan, obtained at 6 months postpartum, showed high normal uptake (17% and 32% at 4 hours and 24 hours respectively), suggestive of recovery phase of PPT. The most recent TSH was elevated at 8.5 UIU/mL and Free T4 was low at 0.7 ng/dL. Disease course was consistent with PPT. Conclusion: The Th1 (T-helper) lymphocyte immune predominance in autoimmune thyroid disease and SLE is the immune-pathogenetic base of the association between both diseases. Postpartum thyroiditis is a variant of chronic autoimmune thyroiditis. Serum anti-TPO antibodies vary during pregnancy and tend to increase early and may decline later. Immunologic tolerance increases during pregnancy, fades in the postpartum period and makes interpretation of thyroid function tests and disease process challenging. Pregnant and postpartum patients who have SLE have increased prevalence of thyroid disease. Causes are multifactorial with a higher prevalence of hypothyroidism and thyroid autoantibodies. Hyperthyroidism is much less likely. One comparable study found 6 of 43 (14%) women with SLE developed PPT and only one of these patients had positive thyroid antibodies. These reports and our patient illustrate the variability of thyroid function tests in patients with SLE.

Hurthle Cells Adenoma With Distant Metastases Refractory to Radioiodine

Introduction: Adenoma of the thyroid is defined as an encapsulated follicular tumor that is well delimited in relation to the adjacent parenchyma and whose cells do not exhibit the nuclear alterations of papillary thyroid carcinoma (PTC), and in the absence of capsular and vascular invasion. Adenoma, including the of Hurthle cells, is considered a benign tumor. No additional treatment is recommended after resection of the tumor. Case: A 64-year-old man was submitted to total thyroidectomy because of a nodule measuring 3.5 cm with indeterminate cytology (predominance of Hurthle cells). Histology revealed an Hurthle cells adenoma of 3.2 cm. The tumor did not exhibit vascular or capsular invasion, the cells did not contain nuclei of PTC, and no necrosis or mitoses were observed. Five years after surgery, serum thyroglobulin (Tg) was elevated (25 ng/ml) during euthyroidism (TSH 0.6 mUI/l) and in the absence of anti-Tg antibodies. Serum calcitonin was undetectable. The patient developed a progressive increase in Tg and neck ultrasonography (US), chest computed tomography (CT), and FDG-PET/CT were performed. US revealed atypical lymph nodes (the largest with 12 mm) and cytology showed abundance of Hurthle cells. Chest CT detected multiple nodules, the largest measuring 15 mm, and FDG-PET/CT revealed areas of cervical and pulmonary uptake corresponding to the lesions seen on US and CT. The patient received 100 mCi radioactive iodine and post-therapy whole-body scanning showed mild uptake only in the thyroid bed. The patient continues to show progressive increase in Tg (last measurement > 1,000 ng/ml), as well as progression of metastases. He remains under follow-up and on therapy with tyrosine kinase inhibitor. The histology result was revised by two pathologists with broad experience in thyroid pathology who confirmed the initial findings compatible with adenoma. Conclusion: The present case shows that, although rare, Huthle cells tumors can develop metastases even when the tumor is < 4 cm and unequivocally without nuclei of PTC or capsular and vascular invasion, thus considered benign (adenoma). As observed in this case, these metastases can be macrometastases, distant, and refractory to radioiodine. Reference: Lloyd RV, Osamura RY, Klöppel G, Rosai J, ed. WHO Classification of Tumours of Endocrine Organs. 4th edition Lyon: IARC; 2017

A Joint Statement from the American Thyroid Association, the European Association of Nuclear Medicine, the European Thyroid Association, the Society of Nuclear Medicine and Molecular Imaging on Current Diagnostic and Theranostic Approaches in the Management of Thyroid Cancer.

Background: The American Thyroid Association (ATA), the European Association of Nuclear Medicine, the European Thyroid Association, and the Society of Nuclear Medicine and Molecular Imaging have established an intersocietal working group to address the current controversies and evolving concepts in thyroid cancer management and therapy. The working group annually identifies topics that may significantly impact clinical practice and publishes expert opinion articles reflecting intersocietal collaboration, consensus, and suggestions for further research to address these important management issues. Summary: In 2019, the intersocietal working group identified the following topics for review and interdisciplinary discussion: (i) perioperative risk stratification, (ii) the role of diagnostic radioactive iodine (RAI) imaging in initial staging, and (iii) indicators of response to RAI therapy. Conclusions: The intersocietal working group agreed that (i) initial patient management decisions should be guided by perioperative risk stratification that should include the eighth edition American Joint Committee on Cancer staging system to predict disease specific mortality, the modified 2009 ATA risk stratification system to estimate structural disease recurrence, with judicious incorporation of molecular theranostics to further refine management recommendations; (ii) diagnostic RAI scanning in ATA intermediate risk patients should be utilized selectively rather than being considered mandatory or not necessary for all patients in this category; and (iii) a consistent semiquantitative reporting system should be used for response evaluations after RAI therapy until a reproducible and clinically practical quantitative system is validated.

MON-448 Detection of Thyroid Cancer Recurrence in Patients with Positive Thyroglobulin Antibody Receiving Immunoglobulin Therapy

Introduction: Differentiated thyroid cancers such as papillary and follicular thyroid cancer make up more than 90% of all thyroid cancers. The presence of thyroglobulin autoantibodies makes interpretation of the thyroglobulin level unreliable, as it could be falsely low or falsely high. Studies have shown that rising thyroglobulin antibody levels, could be used to monitor for disease recurrence in patients with negative thyroglobulin and imaging studies. However, there are challenges in detecting recurrence in patients with normal thyroglobulin level and thyroid imaging studies, who are on lifelong immunoglobulin therapy and who have increasing thyroglobulin antibody levels.Clinical case: A 63 yr old female was found to have an incidental left thyroid nodule at age 48yrs from a carotid ultrasound. She underwent US guided FNA of the thyroid nodule and was found to have papillary thyroid cancer. She had total thyroidectomy a month later, with removal of a 1.4cm primary, with no evidence of extrathyroidal extension, clear margins and no evidence of lymphovascular invasion – Stage T1bN0M0. There was left level 6 neck dissection with no carcinoma identified in the 2 lymph nodes removed. She received 105.3 mCi radioactive iodine (RAI) and whole body thyroid scan done 7 days later revealed, increased uptake involving the thyroid bed likely residual thyroid tissue. Activity was noted inferolateral to the right thyroid bed which most likely represents a lymph node. There was no evidence of distant metastasis.She was commenced on levothyroxine post operatively. Her other past medical history is significant for idiopathic urticaria and angioedema, immune deficiency disorder with low IgG and IgM and asthma. She was commenced on monthly IV immunoglobulins 5yrs post RAI therapy, due to recurrent sinusitis, rhinitis and chronic diarrhea. She was later transitioned to weekly SQ immune globulin – Hizentra which she is on till date.Over the past 15 years, serial neck ultrasounds post radioiodine ablation have been negative for recurrence. Her TSH ranged 14.91 to 0.04 (ref 0.27-4.2 uiu/ml) and thyroglobulin (Tg) titer remains <0.1 (ref <0.1). Her thyroglobulin antibody titers have trended up from <0.2 (ref <2.0) 5yrs post RAI therapy to 49 (ref <4 iu/ml)) on her most recent test this year. She is currently undergoing further work up to rule out recurrence of her cancer. In our review of the literature we found one report that showed use of Liquid Chromatography–Mass Spectrometry (LC-MS) was able to differentiate thyroid cancer recurrence in an individual with positive antithyroglobulin antibody receiving immunoglobulin therapy.Conclusion: In patients with negative Tg levels, but elevated thyroglobulin antibody while receiving immune globulin therapy, thyroglobulin antibody levels may not be a reliable indicator of thyroid cancer recurrence. Measurement of Tg levels using a LC-MS may provide some clarity.