Diffuse Thyroid Uptake Research Articles

8477 Medullary Thyroid Carcinoma Masquerading as a Cold Nodule in a Patient With Graves' Disease

Abstract Disclosure: T. Umashree: None. K.J. Farooqui: None. A. Mithal: None. Background: Only a handful of cases of MTC have been reported in the setting of Graves’ disease. Clinical Case: A 38 year old lady presented with symptoms of significant weight loss and palpitations for past six months. Thyromegaly was present, with non tender left lobe enlargement of about 3x3 cm. On further probing it was found that her father had been operated for thyroid cancer 22 years ago, the type of which patient was not aware of. TFTs reflected a thyroxtoxic state (TSH -<0.01mIU/mL [0.34-5.6] FT4 - 3.38 ng/dL [0.58-1.64] FT3 - 8.46 pg/mL [2.6-4.2]) and TRAb was positive (8.74 IU/L [<1.22]). USG neck revealed a hypoechoic lesion of 18x18x13 mm in left lobe thyroid with internal calcifications, with multiple bilateral non-significant lymph nodes. Technetium99 (Tc99) scan showed an enlarged left lobe, with diffuse thyroid uptake at 20 minutes of 4%, and a well-defined photopenic area in left lobe, corresponding to the nodule seen on USG. FNAC of the nodule was suggestive of Hürthle cell neoplasm and patient underwent left hemithyroidectomy. Surprisingly, HPE was consistent with medullary thyroid cancer. Serum calcitonin was raised at 148 pg/mL (N<4.8 for females) and plasma free metanephrines and normetanephrine were normal. F-18 DOPA PET CT showed uptake in residual right lobe of thyroid only, no other abnormal uptake was seen. She underwent completion thyroidectomy with central compartment clearance and is now under regular follow up. Genetic analysis showed RET gene mutation of Cys634Ser, which is heterozygous for MTC. Cold nodules in Graves’ disease should be viewed with suspicion, and while PTC and FTC have been reported more commonly, MTC is extremely rare in this setting. A calcitonin washout of the FNAC may have prevented this patient from undergoing two surgeries. Moreover, Hürthle cell change can also occur in C-cells of the thyroid, not just the follicular cells. Lastly, given the history of thyroid cancer in her father, index of suspicion of MTC should have been higher in this patient. Conclusion: Cold nodules in Graves’ Disease may be malignant, and should always be examined by FNAC. Though MTC is rare, it is not unknown in Grave’s disease. Presentation: 6/3/2024

7699 Unanticipated Harmony: PD-L1 Inhibitor Treatment for Urothelial Cancer Resolving Graves' Disease in a Patient - A Case of Immune Modulation Surprises

Abstract Disclosure: K. Tiwari: None. C.A. Resta: None. Introduction: Programmed death ligand 1(PD-L1) inhibitors constitute a class of immune checkpoint inhibitors (ICI) employed in treating various cancers. Thyroid-related immune-related adverse events (irAEs), such as hypothyroidism, are found to be in 3.9% of patients with PD L1 treatments. This case explores a unique scenario where a patient with pre-existing Graves' disease, undergoing PD-L1 inhibitor therapy for cancer, experienced an unexpected sequence of events leading to the default treatment of Graves' disease and subsequent progression to hypothyroidism. Case Presentation: A 59-year-old male, who had been effectively managed on methimazole for Graves' disease over two years and had chosen not to pursue definitive therapy for the condition, presented with tremors and a bilaterally enlarged thyroid gland during treatment for urothelial carcinoma. Laboratory findings included a TSH of 0.03 mIU/L (nl 0.40-4.50 mIU/L), fT4 of 3.4 ng/dL (nl 0.8-1.8 ng/dl), and tT3 of 284ng/dl (nl 76-181 ng/dl). The patient had recently started treatment with Avelumab, a PD-L1 inhibitor, as maintenance therapy following 4 cycles of gemcitabine/cisplatin cycles. Concerned about worsening Graves' disease, the methimazole dose was increased, and follow-up labs were performed after three weeks. These results showed low-normal fT4 of 0.8 ng/dL, TSH of 1.01 mIU/L(N), and low T3 of 58 ng/dL. TSI was mildly elevated at 168%. Due to rapidly changing thyroid function tests and suspicion of thyroiditis, methimazole was stopped. A PET scan a week later indicated diffuse thyroid uptake consistent with thyroiditis. Repeat labs 10 days later revealed a TSH of 67.36 mIU/L(H) and fT4 of 0.4 ng/dL(L), indicative of overt primary hypothyroidism. The patient exhibited symptoms including fatigue, constipation, and cold intolerance. The patient was initiated on levothyroxine therapy to address overt primary hypothyroidism, likely secondary to destructive thyroiditis from ICI. Discussion: Thyroid irAEs are typically incidentally discovered during routine monitoring of ICI treatment. It includes thyrotoxicosis, subclinical hypothyroidism, and overt hypothyroidism. These events commonly occur in patients lacking pre-existing thyroid conditions. In contrast, our patient, with a history of Graves' disease, experienced resolution of Graves' disease following treatment with PD-L1 inhibitor use with subsequent progression to hypothyroidism. Conclusion: This case emphasizes the importance of recognizing atypical presentations of thyroid irAEs in individuals with pre-existing thyroid disorders undergoing ICI treatment. Presentation: 6/3/2024

Significance of incidental thyroid 18 F-fluorocholine uptake in patients with hyperparathyroidism imaged for localizing hyperfunctioning parathyroid glands.

18 F-fluorocholine PET/CT is considered the imaging gold standard for detection of hyperfunctioning parathyroid glands . However, increased uptake might also occur in the thyroid gland. The aim of our study was to assess the incidence and significance of 18 F-fluorocholine uptake in the thyroid gland in patients with hyperparathyroidism. This retrospective study includes 195 consecutive patients with hyperparathyroidism, who underwent 18 F-fluorocholine PET/CT, for detection of hyperfunctioning parathyroid glands. PET/CT images were reviewed by two nuclear medicine physicians for the presence of focal or diffuse thyroid uptake. PET/CT results were compared with laboratory parameters, ultrasonography, EU-TIRADS classification in the presence of thyroid nodules, cytology, and final histology. 25 patients (13%) showed 18 F-fluorocholine uptake in the thyroid gland: focal thyroid uptake (FTU) in 7 patients (4%), diffuse thyroid uptake (DTU) in 8 patients (4%), and combined uptake (FTU + DTU) in 10 patients (5%), with a total of 20 active thyroid nodules. There was no correlation between EU-TIRADS classification and PET parameters. One highly 18 F-fluorocholine active thyroid nodule and one isoactive thyroid nodule turned out to be papillary thyroid cancers in the final histology; 50% of the patients with DTU had Hashimoto's thyroiditis. Incidental 18 F-fluorocholine uptake in the thyroid gland was observed in 13% of patients. As reported for 18 F-FDG, focal 18 F-fluorocholine uptake might represent thyroid cancer and should be evaluated with ultrasound and, if indicated, with fine-needle aspiration cytology. Diffuse 18 F-fluorocholine uptake most likely represents multinodular goiter or Hashimoto's thyroiditis.

Asymmetric diffuse thyroid uptake on 18F-FDG PET/CT in patient with subacute thyroiditis: Case report and literature review.

A 48-year-old man with an intermittent fever of 39.0oC for more than three weeks underwent computed tomography (CT) and blood testing, which revealed no clues. Antibiotics wereadministered, but his condition did not improve. Fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) showed right-lobe-dominant diffuse thyroid uptake. On technetium-99m (99mTc) pertechnetate scintigraphy, the thyroid gland could not be visualized, and he was diagnosed with subacute thyroiditis (SAT). When asymmetric 18F-FDG diffuse thyroid uptake on PET/CT is observed in a patient with a fever of unknown origin (FUO), SAT may need to be considered.

Early post-treatment 18F-FDG PET/CT for predicting radiation-induced hypothyroidism in head and neck cancer

BackgroundRadiation-induced hypothyroidism (RIHT) is a common, but underestimated, late adverse effect in head and neck cancer. We investigated the value of early post-treatment 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for predicting RIHT.MethodsWe searched our institutional database for patients aged ≥ 20 years who had undergone definitive radiotherapy for nasopharyngeal or oropharyngeal cancer between 2005 and 2017, followed by 18F-FDG PET/CT within 180 days of radiotherapy completion. We visually assessed and compared PET/CT and baseline characteristics in patients with and without RIHT using the chi-square test for categorical variables and the t-test for continuous variables. Variable predictive ability was evaluated by measuring the area under receiver operating characteristic curves.ResultsFifty-two patients were included; 22 (42%) developed RIHT and 30 (58%) did not. Two patients presented with diffuse thyroid uptake on PET/CT via visual assessment, and both developed RIHT later. Among the PET/CT variables, thyroid functioning volume was significantly higher in patients without RIHT than in patients with RIHT (16.30 ± 6.03 cm3 vs. 10.61 ± 3.81 cm3, p < 0.001). The maximum standard uptake values of the thyroid and pituitary glands did not differ significantly between the groups. Two patient characteristics, pretreatment thyroid volume and mean radiotherapy dose to the thyroid, also showed significant differences between the groups. An algorithmic approach combining visual grading of thyroid 18F-FDG uptake and thyroid functioning volume cutoff of 14.01 yielded an area under curve of 0.89 (95% confidence interval, 0.80–0.98); the sensitivity, specificity, positive predictive value, and negative predictive value were 87.0%, 82.3%, 80.0%, and 88.9%, respectively.ConclusionEarly post-treatment PET/CT-derived thyroid functioning volume was a good predictor of RIHT development. Diffusely increased thyroid 18F-FDG uptake on PET/CT may indicate impending RIHT. Routine surveillance of thyroid function is warranted in patients at high risk of developing RIHT.

Diffuse Thyroid Uptake in FDG PET/ CT Scan cCan Predict Subclinical Thyroid Disorders

Background: 18F-FDG positron emission tomography (PET) has established itself in the field of oncology and it is useful in the initial staging and follow-up of a variety of malignancies. Significant thyroid uptake is often identified as an accidental finding on whole-body positron emission tomography for non-thyroid disease. Aim of this study: to investigate the effect of 18F-FDG on thyroid gland function after performing PET scan compared to thyroid function prior to scan. Materials and Methods: 43 subjects who had an 18F-FDG PET scan as part of a cancer screening program participated in this study. All cancers are diagnosed using 18F-FDG, except for prostate cancer, brain cancer and neuro-endocrine tumors, which are diagnosed using Ga-68. Thyroid stimulating hormone (TSH), thyroxine (T4), and triiodothyronine (T3) were measured. Results: Clinical information and results of thyroid function tests were available for 43 patients. Twenty- three out of 43 patients (53.48%) had abnormally high TSH levels with incident hypothyroidism, while 20 out of 43 patients (46.51%) had abnormally low TSH levels with incident hyperthyroidism, and the association was significant (p &lt;0.05). Conclusion: Thyroid hormone abnormality is strongly associated with the degree of diffuse thyroid uptake on 18F-FDG PET. As a result, an autoimmune process could be the most likely pathological cause of diffuse thyroid uptake.

Thyroid 18F-fluorocholine uptake in patients with chronic autoimmune thyroiditis.

Objective18F-Fluorocholine (18FCH) PET/CT has high sensitivity for parathyroid adenoma detection and can reliably exclude malignancy in thyroid nodules with indeterminate cytology. Data regarding 18FCH uptake in chronic autoimmune thyroiditis (CAT) are scarce. We aimed to assess thyroid 18FCH uptake in CAT with biological and histological correlation.Methods This is an ancillary study from the Chocolate trial (NCT02784223) that prospectively enrolled 107 patients planned for thyroid surgery. 18FCH PET/CT acquisitions were performed 20 and 60 min after injection. 18FCH uptake in the thyroid gland was assessed by measuring maximum (SUVmax) and mean (SUVmean) standardized uptake values. Thyrotropin, free thyroxine (FT4), thyroid peroxidase antibodies (TPOAb) and thyroglobulin antibodies were collected. The intensity of thyroiditis and the degree of fibrosis were assessed on pathology.Results CAT was evidenced in 19/107 (18%) patients. Of these, 13 (68%) displayed an increased and diffuse 18FCH thyroid uptake. This uptake pattern was not observed in patients without CAT. SUVmax and SUVmean were higher in patients with CAT than in those without (P < 0.001). At both acquisition times, SUVmax showed a monotonic relationship with the intensity of thyroiditis (Spearman ρ = 0.44 and 0.51, respectively, P < 0.001) and with the degree of fibrosis (Spearman ρ = 0.55 and 0.62, respectively, P < 0.001). SUVmax showed a linear relationship with TPOAb titers at 20 min (Pearson r = 0.54, P < 0.05; Spearman ρ = 0.59, P = 0.03).Conclusions More than two-thirds of the patients with CAT present high and diffuse thyroid 18FCH uptake. This uptake pattern is highly specific to CAT and is correlated with pathology and TPOAb titers.

Clinical Significance of Diffusely Increased Uptake of 68Ga-FAPI in Thyroid Gland.

Purpose: To determine the clinical significance of diffuse uptake of 68Ga-FAPI in the thyroid.Methods: From January 2020 to September 2021, all subjects with diffuse thyroid uptake in 68Ga-FAPI PET/CT were investigated in our hospital, and compared with the age and sex matched control group. The 68Ga-FAPI uptake in the thyroid gland was analyzed semi-quantitatively using the maximum standardized uptake value (SUVmax), and regression analysis was used to analyze the correlation between available serum thyroid stimulating hormone (TSH) and thyroid peroxidase antibody (TPOAb).Results: Among 815 subjects, 39 subjects were found diffuse FAPI uptake in thyroid gland; 11 subjects refused further examination; a total of 28 subjects were included in the analysis, and 27 subjects were diagnosed with chronic thyroiditis (including 20 subjects with Hashimoto's thyroiditis), 3 subjects with Grave's disease, 3 subjects with only serum TSH elevated, and 1 subject with malignant of thyroid and thyroiditis. The SUVmax of 27 subjects with thyroiditis was 5.75 ± 5.45. No significant correlation was found between the SUVmax and the level of serum TSH (P = 0.389) or TPOAb (P = 0.426).Conclusion: The incidentally discovered diffusely increased 68Ga-FAPI uptake in the thyroid gland is mostly related to chronic lymphocytic (Hashimoto's) thyroiditis. 68Ga-FAPI uptake level correlated neither with the degree of hypothyroidism nor with the titer of TPOAb. In addition, immune-related thyroiditis with immune checkpoint inhibitors may be accidentally found on 68Ga-FAPI, which may be helpful in facilitate timely intervention.

O15 Tumour-induced osteomalacia: a diagnostic challenge

Case report - IntroductionTumor-induced osteomalacia is a rare acquired metabolic bone disorder characterised by isolated renal phosphate wasting due to abnormal tumour production of fibroblast growth factor 23 (FGF23). Bloods show hypophosphatemia. However, given the lack of awareness of this disease, and the non-specific nature of the presenting symptoms, diagnosis is often delayed for years or even missed.With this case report, we want to shed light on this rare bone disorder and highlight the importance of not ignoring a low phosphate level.Case report - Case descriptionWe report the case of a 63-year-old gentleman who presented to us with a history of progressive bone pain, marked muscle weakness and fatigue. He had a persistently raised parathyroid hormone and very high alkaline phosphatase. Calcium was low normal, but vitamin D was normal. Phosphate was noted to be low and had been so since 6 years prior to being referred. X-ray pelvis showed sclerotic-looking iliac bones, but an isotope bone scan showed no evidence of metastatic disease.We referred him to our endocrinology colleagues to investigate for possible primary hyperparathyroidism. However, ultrasound scan of neck showed no abnormal parathyroid gland. PET and CT scan of the chest, abdomen and pelvis did not show any significant pathology. MIBI scan of parathyroid glands showed diffuse thyroid uptake. The SPECT-CT images showed a well-defined focal area of increased activity, posterior to the mid/lower pole of the right thyroid lobe, possibly indicative of hyperfunctioning parathyroid tissue. The radiologist questioned the possibility of renal osteodystrophy and resultant secondary hyperparathyroidism. However, there was no evidence for renal dysfunction with a creatinine of 80 umol/L.We referred this gentleman to the Oxfordshire Osteoporosis and Metabolic Bone Service. Bloods showed a raised P1NP. This was felt to be consistent with tumour-induced osteomalacia. Oversecretion of FGF23 was confirmed and DOTATATE scan revealed two areas of uptake: one in the right hip and one in the skull.Meanwhile, the patient had been started on Sandoz Phosphate and alfacalcidol, and his bone aches improved on this combination therapy.He had radio-ablation of the hip lesion this year and has now stopped all his medication. His fatigue and muscle strength has improved dramatically. The skull lesion is being monitored for now with yearly imaging and follow-up in the metabolic bone clinic.Case report - DiscussionTumour-induced or oncogenic osteomalacia is extremely rare. Symptoms include chronic muscle and bone pain, weakness, and fatigue and can result in fragility fractures due to osteomalacia. Lack of awareness of these clinical manifestations and relevance of low phosphate levels often leads to a diagnostic delay or misdiagnosis. As seen in our case, it took multiple investigations and almost 2 years before this gentleman had a confirmation of his diagnosis.The pathogenesis of tumour-induced osteomalacia involves tumour expression of fibroblast growth factor 23. This hormone inhibits reabsorption of phosphate in the proximal renal tubule and down-regulates renal conversion of 25-hydroxyvitamin D to its active form, 1,25-dihydroxyvitamin D. Replacing phosphate on its own paradoxically increases PTH levels. The metabolic abnormalities may be partially or completely corrected with phosphate supplementation and calcitriol. In our patient, his PTH levels remained elevated, but alkaline phosphatase improved, as did calcium and phosphate levels.Unlike many other causes of osteomalacia, tumour-induced osteomalacia is curable by resection of the offending tumour. However, finding the responsible FGF23-secreting tumour can be incredibly challenging. There is ongoing research into medical treatment for this condition, especially if the tumour is not found or is unresectable, or the patient is not a surgical candidate.Case report - Key learning pointsLow phosphate levels can be easily overseen, with significant consequences. This case emphasises the need to recognise hypophosphatemia and to look for its cause. Conversely, it also illustrates the need to investigate all patients with persistent musculoskeletal symptoms for hypophosphatemia.Our case underscores the importance of being aware of the rare condition of tumour-induced osteomalacia. This will enable early recognition and treatment of the metabolic abnormality, before the development of any deleterious effects of osteomalacia on the skeleton.

Case Report: Primary Hypothyroidism Associated With Lutetium 177-DOTATATE Therapy for Metastatic Paraganglioma

BackgroundLutetium 177 (177Lu) - DOTATATE is a form of peptide receptor radionuclide therapy (PRRT) utilized in the treatment of neuroendocrine tumors. Data on 177Lu-DOTATATE-induced thyroid dysfunction is limited.Case DescriptionA 29-year-old male with SDHB positive metastatic paraganglioma enrolled under the 177Lu-DOTATATE trial (NCT03206060) underwent thyroid function test (TFT) evaluation comprised of thyroid stimulating hormone (TSH) and free thyroxine (FT4) immunoassay measurements per protocol prior to 177Lu-DOTATATE therapy. The TSH was suppressed [<0.01 µIU/ml (0.27–4.2 µIU/ml)], and FT4 was normal [1.3 ng/dl (0.9–1.7 ng/dl)]. The TSH receptor antibody and thyroid stimulating immunoglobulin index were undetectable [<1 IU/L (≤1.75 IU/L), and <1 (≤1.3) respectively], while the anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-Tg) antibodies were elevated [605 IU/ml (0.0–34.9 IU/ml), and 178 IU/ml (0.0-40.0 IU/ml) respectively]. Mass spectrometry on a stored (-80°C) plasma sample obtained one-month pre-PRRT revealed elevated total triiodothyronine (TT3) [235 ng/dl (65–193 ng/dl)] and FT4 [3.9 ng/dl (1.2–2.9 ng/dl)] levels. The patient was diagnosed with Hashimoto’s thyrotoxicosis. However, the patient was asymptomatic. One month after the first dose of 200mCi 177Lu-DOTATATE, the patient noted fatigue and a 2.6 Kg weight gain. The TSH (73.04 µIU/ml), anti-TPO antibodies (>1,000 IU/ml), and anti-Tg antibodies (668 IU/ml) had substantially increased, with reductions in FT4 (0.3 ng/dl) and TT3 [54 ng/dl (87–169 ng/dl)]. Diagnostic gallium 68 - DOTATATE positron emission tomography-computed tomography performed prior to 177Lu-DOTATATE treatment revealed diffuse thyroid uptake. Post-therapy single-photon emission computed tomography also revealed diffuse uptake of 177Lu-DOTATATE in the thyroid gland. Levothyroxine therapy was initiated, and the patient’s symptoms resolved.SummaryWe report, for the first time, a patient with asymptomatic primary hyperthyroidism who rapidly developed symptomatic primary hypothyroidism 1 month after 177Lu-DOTATATE therapy, accompanied by marked changes in TFTs and thyroid auto-antibody titers, with functional imaging evidence of diffuse uptake of 177Lu-DOTATATE in the thyroid gland.ConclusionsThyroid dysfunction can be associated with PRRT. Thyroid uptake patterns on pre-treatment diagnostic somatostatin analog scans might predict individual susceptibility to PRRT-associated TFT disruption. Therefore, periodic evaluation of TFTs should be considered in patients receiving PRRT.

SAT-497 Conversion of Hashimoto’s Thyroiditis to Grave’s Disease: A Case Report

Introduction: Hashimoto’s thyroiditis and Grave’s disease are common causes for autoimmune thyroid disease. Conversion from Grave’s disease to hypothyroidism have been previously reported in literature. But development of Grave’s disease after a long standing hypothyroidism rarely occurs.Case report: a 22 -year-old Saudi pregnant female patient, was diagnosed with subclinical hypothyroidism with positive anti -thyroid peroxidase antibodies (Anti-TPO) in 2009. She was started on thyroxin and eventually became euthyroid with normal TSH levels till 2016. During subsequent follow-ups, patient was increasingly complaining of palpitations, weight loss and fine tremors. Thyroid function revealed increasingly suppressed TSH levels and over-replacement was suspected. Thyroxin dose was then gradually reduced and finally stopped for few months. Yet her symptoms persisted. Repeated thyroid function showed suppressed TSH level and elevated T4, T3 levels in keeping with overt hyperthyroidism. Thyroid scan further confirmed the diagnosis with diffuse thyroid uptake suggestive of Grave’s disease.Patient was started on medical treatment initially, then successfully treated with radioactive ablation.Conclusion: Although it rarely occurs, possibility of conversion from hypothyroidism to hyperthyroidism should always be kept in mind while treating hypothyroid patients with persistent clinical or biochemical evidence of hyperthyroidism despite dose reduction.

Detection of thyroiditis on PET/CT imaging: a systematic review.

The incidence and clinical significance of thyroiditis detected by molecular imaging methods is a clinical challenge that is not widely investigated in the literature. The aim of this systematic review was to analyze published data about the detection of thyroiditis on PET or PET/CT using different tracers. A comprehensive computer literature search of the Scopus, PubMed/MEDLINE, Embase, and Cochrane library databases was conducted up to November 2019 to find relevant papers on the detection of thyroiditis by PET/CT, the metabolic appearance, and the clinical significance. Twenty-six articles were selected and retrieved in full-text version. From the analyses of these studies, the following main findings have been found. Diffuse thyroid uptake of PET tracers is a relatively frequent event, ranging from 0.4 to 46.2%, and it is commonly related to benign disease. Thyroiditis is the most frequent reason for diffuse increased thyroid 18F-FDG uptake. Cases of malignant disease with a pattern of diffuse 18F-FDG thyroid uptake are less frequent. Preliminary studies show a possible role of thyroiditis detected by 18F-FDG PET/CT in evaluating treatment response and as a prognostic marker in oncological patients treated with immunotherapy. However, further studies are needed. Diffuse 18F-FDG thyroid uptake is a relatively rare event commonly due to benign diseases, among which thyroiditis is the most common. The rate of neoplastic disease with diffuse 18F-FDG thyroid uptake is very low. Diffuse 18F-FDG thyroid uptake requires further investigation and clinical evaluation for the correct diagnosis. Currently, cases of diffuse thyroid uptake with non-18F-FDG radiotracer are only anecdotal.

Diffusely Increased 18F-FDG Uptake in the Thyroid Gland and Risk of Thyroid Dysfunction: A Cohort Study.

The impact of incidentally identified diffuse thyroid FDG uptake on 18F-FDG PET/CT scan on the incidence of thyroid dysfunction remains unclear. We examined the association of diffuse thyroid FDG uptake with the development of thyroid dysfunction. This cohort study involved 39,098 Korean adults who were free of malignancy and thyroid disease at baseline and underwent regular health checkup examinations including an 18F-FDG whole body PET/CT scan, thyroid-stimulating hormone and free thyroxine. The participants were annually or biennially followed for up to 5 years. A parametric proportional hazard model was used to estimate the adjusted hazard ratio (HR) and 95% confidence interval (CI). Diffuse thyroid uptake was positively associated with increased risk of thyroid dysfunction in both the cross-sectional and cohort studies. During 104,261.4 person-years of follow-up, 102 incident hypothyroidism cases and 172 hyperthyroidism cases were identified. Multivariable-adjusted HR (95% CI) for incident hypothyroidism or hyperthyroidism comparing diffuse thyroid uptake to no uptake were 15.72 (9.23–26.77) and 7.38 (4.23–12.87), respectively. In this large cohort, incidentally, identified diffuse thyroid uptake on 18F-FDG PET/CT was associated with increased risk of both prevalent and incident thyroid dysfunction. Therefore, baseline and follow-up evaluations in individuals with diffuse thyroid uptake may help identify individuals with thyroid dysfunction.

Evaluation of Incidental Thyroid Findings Detected by Positron Emission Tomography/Computed Tomography

AbstractBackground: Thyroid incidenteloma detected on 18F-FDG PET/CT carries a high risk of malignancy. This high risk of malignancy supports the performance of a further diagnostic procedure, such as ultrasonography and fine needle aspiration biopsy.Aim of Study: To determine the role of PET/CT in evalu-ation of incidental thyroid lesions detected in patients being studied for lymphomas and/or cancers other than of thyroid.Material and Methods: This study included thirty four patients with incidental abnormal increased FDG uptake. All patients were subjected to ultrasound examination and patients with focal increased tracer uptake were subjected to fine needle aspiration biopsy.Results: This study included a total of 1263 consecutive patients who underwent a FDG PET/CT study for staging of an advanced cancer of any site of the body other than the thyroid gland during the period. An incidental abnormal increase in FDG uptake in the thyroid gland was observed in 39 (3.08%) patients. Out of these patients, 26/39 (66.6%) presented with a focal and 13/39 (33.4%) with a diffuse thyroid uptake giving a prevalence of 2.06% for focal uptake and 1.03% for diffuse uptake. Six patients out of 23 patients with focal abnormal thyroid uptake were proven to have thyroid malignancy (Four patients with papillary thyroid carcinoma, one patient with follicular thyroid carcinoma and the remaining patient with atypical Hurthle cells). Thus the malignancy rate in patients with thyroid incidentalomas which proceeded to tissue biopsy was about 26%.Conclusion: An incidental focal uptake of 18F-FDG in the thyroid gland is of significant risk of malignancy. A high value of SUVmax increases the risk of malignancy and SUVmax does not correlated with the diameter of malignant lesions, so FDG-PET/CT can detect malignancy in small thyroid lesions.

Correlation between anti-thyroid peroxidase antibody levels and diffuse thyroid uptake of 18F-fluorodeoxyglucose in Hashimoto\u2019s thyroiditis: a retrospective study

BackgroundOn 18F-fluorodeoxyglucose (FDG)-positron emission tomography (PET), diffuse uptake in the thyroid gland is often observed in patients with Hashimoto’s thyroiditis. In this study, we evaluated the factors associated with diffuse uptake by comparing Hashimoto’s thyroiditis patients with or without diffuse uptake in the thyroid.MethodsA retrospective study was conducted of 18 patients with Hashimoto’s thyroiditis who underwent blood tests, thyroid ultrasonography, and FDG-PET during the period from 2014 to 2015. The patients were divided into two groups: one with diffuse thyroid uptake (group 1, n = 13) and one without diffuse thyroid uptake (group 2, n = 5). Clinical and laboratory parameters, including maximum standardized uptake in the thyroid (SUVmax), which was defined as the higher value obtained in either the right or left thyroid lobe, were compared in the two groups.ResultsThe frequency of abnormal findings, such as a rough or heterogeneous pattern, was significantly higher in group 1 (p < 0.01), as were anti-thyroid peroxidase (TPO) antibody titers, anti-thyroglobulin (Tg) antibody titers, and SUVmax (p < 0.01). The frequency of hypothyroidism did not differ significantly in the two groups. Anti-TPO and anti-Tg titers were positively correlated with SUVmax (r = 0.856, p < 0.01 and r = 0.821, p < 0.01, respectively); in univariate analysis, anti-TPO titer was predictive of SUVmax (p < 0.01).ConclusionsThe results of the current study suggest that Hashimoto’s thyroiditis patients with high titers of anti-thyroid antibodies are likely to exhibit intense diffuse FDG uptake in the thyroid, and that thyroid function may be clearly impaired, even in the presence of mild FDG uptake in the thyroid.

Clinical significance of patterns of increased [18F]-FDG uptake in the thyroid gland: a pictorial review

In the diagnosis and staging of oncologic patients, [18F]-fluorodeoxyglucose positron emission tomography (FDG-PET) is well recognized as an important functional imaging modality. FDG-PET also has been used for cancer screening in healthy individuals. In general, the normal thyroid gland shows absent or low uptake on FDG-PET, which is often identified as an incidental finding on PET. Today, thyroid FDG uptake can be seen in three patterns: diffuse; focal; and diffuse-plus-focal. Diffuse thyroid uptake is mainly considered an indicator of chronic thyroiditis. Focal thyroid uptake has been associated with malignancy (range 25-50%). Diffuse-plus-focal uptake is not well recognized and might also indicate a risk of malignancy. Understanding the patterns of thyroid FDG uptake is thus important for nuclear medicine physicians or radiologists when giving recommendations to the referring physician. In this pictorial review, we show the clinical significance of different patterns of thyroid uptake on FDG-PET [PET/computed tomography (CT)], including ultrasonography (US) findings.

How often do we see incidental 68Ga-DOTATATE thyroid uptake in PET/CT in patients with neuroendocrine tumours?

Thyroid diseases, which may occur as focal or diffuse changes in thyroid parenchyma, are most often observed in women. Our aim was to assess the prevalence of incidental thyroid uptake of 68Ga-DOTATATE PET/CT in patients referred to the Nuclear Medicine Department for evaluation of neuroendocrine neoplasia (NEN). We retrospectively evaluated 1150 68Ga-DOTATATE PET/CT images. Clinical history, serum TSH and thyroid antibody (TAb) concentrations, ultrasonography, and cytological assessment of the material from fine-needle aspiration biopsy (FNA) of the thyroid lesion were investigated. We found incidental abnormalities in 46/1150 (4.1%) patients (12 men, 34 women). 34/46 patients (8 men, 26 women) showed diffuse 68Ga-DOTATATE thyroid uptake, with mean SUVmax 4.6 ± 1.6. Based on laboratory tests and ultrasound, we found: 38% of patients with an active autoimmune thyroiditis, 27% with benign goitre, and 6% with multinodular goitre with autoimmune thyroiditis. The remaining 29% of patients did not show any pathology. In 12/47 patients (4 men, 8 women) focal uptake in the thyroid with SUVmax 7.3 ± 3.3 was found. During one-year follow-up, category II and category III lesions (according to Bethesda classification) were revealed in 9/12 (75%) patients and in one patient, respectively. Histopathological examination after surgery revealed papillary thyroid carcinoma in one patient and benign multinodular goitre in another patient. Patients with focal 68Ga-DOTATATE uptake should undergo further examination (FNA) due to potential risk of malignancy. Diffuse 68Ga-DOTATATE uptake was predominantly associated with active autoimmune thyroiditis or benign goitre. The focal lesions and diffuse pathology diseases were frequently seen in women.

Diffuse thyroid 18F-FDG uptake after R-CHOP therapy predicts favorable outcome in patients with DLBCL.

Therapy-induced autoimmunity may mediate the destruction of cancer cells. Previous studies have demonstrated that presence of autoimmune thyroid disorder is associated with favorable outcome in patients with solid cancer. Patients with diffuse large B cell lymphoma (DLBCL) who achieved complete response on positron emission tomography/computed tomography (PET/CT) after rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) therapy were enrolled in this study. The patients with and without diffuse thyroid uptake (DTU) were classified by PET/CT. A total of 270 patients were enrolled in this study. DTU related to autoimmune thyroiditis was present in 61 patients. The median time to DTU detection was 5.7months (range, 0-21.3months). High International Prognostic Index (IPI) score (progression-free survival [PFS], p = 0.001; overall survival [OS], p = 0.008), bulky mass ≥10cm (PFS, p = 0.001; OS, p = 0.001), bone marrow involvement (PFS, p < 0.001; OS, p = 0.001), and DTU after R-CHOP therapy (PFS, p < 0.001; OS, p = 0.001) were significantly associated with PFS and OS. High IPI score (PFS, p = 0.003; OS, p = 0.014), BM involvement (PFS, p = 0.009; OS, p = 0.039), and DTU after R-CHOP therapy (PFS, p = 0.002; OS, p = 0.002) were independently associated with PFS and OS. DTU after R-CHOP therapy independently predicted favorable outcomes in patients with DLBCL.

Diffuse Thyroid Uptake Incidentally Found on18F-Fluorodeoxyglucose Positron Emission Tomography in Subjects without Cancer History

ObjectiveWe investigated the clinical significance of incidental diffuse thyroid uptake (DTU) on 18F-FDG PET in subjects without a history of cancer.Materials and MethodsThis study included 2062 studies from adults who underwent 18F-FDG PET as a cancer screening program. Subjects were divided into the following two groups: with (group I) or without (group II) DTU. The presence of DTU and the thyroid visual grading score were compared with thyroid function tests, serum anti-microsomal antibody (AMA) levels, and the presence of diffuse parenchymal change (DPC) on ultrasonography (USG).ResultsDTU was found in 6.6% of the scans (137/2062). Serum thyroid stimulating hormone (TSH) and AMA levels were significantly higher in group I than in group II. Increased AMA level (55.1%) and DPC (48.7%) were more frequently found in group I (p < 0.001). The proportion of subjects with any abnormal results in serum free thyroxine, triiodothyronine, TSH, or AMA levels or DPC on USG was significantly higher in group I than in group II (71.5% vs. 10.6%, p < 0.001), and was significantly and gradually increased according to the visual grading score group (0 vs. 1-2 vs. 3-4 = 10.6% vs. 58.5% vs. 90.9%, p < 0.001). TSH and is AMA levels were significantly increased according to the visual grading score.ConclusionThe presence or degree of incidental DTU on 18F-FDG PET is closely correlated with increased serum AMA and TSH levels, and the presence of DPC on USG. Therefore, the most plausible pathological cause of DTU may be cell damage by an autoimmune mechanism.

Incidental Diffuse Thyroid 18F-FDG Uptake Related to Autoimmune Thyroiditis May Be a Favorable Prognostic Factor in Advanced Breast Cancer

Patients with breast cancer have a relatively high prevalence of diffuse thyroid uptake of (18)F-FDG related to thyroid autoimmunity. It is postulated that the presence of thyroid autoimmunity has prognostic implications for breast cancer. The aim of this study was to evaluate the prognostic value of incidental diffuse thyroid uptake in breast cancer patients. This was a retrospective observational cohort study in a tertiary referral hospital. We evaluated a total of 564 patients who had undergone surgery for primary breast cancer between January 2006 and December 2009. Patients were divided into 2 groups according to their diffuse thyroid uptake. The main outcome measure was disease-free survival. Of the 564 patients, 108 (19.1%) showed diffuse thyroid uptake. The median follow-up period was 36.0 mo (range, 1.0-77.0 mo). Both thyroperoxidase and thyroglobulin antibody titers were higher in patients with thyroid uptake than in those without (P < 0.001 for both). Of the 108 patients with thyroid uptake, 5 had a recurrence of breast cancer during the follow-up, whereas 85 without uptake had a recurrence (log-rank statics, 12.28; P < 0.001). The association between diffuse thyroid uptake and tumor recurrence was not significant in multivariate analysis of patients with early-stage breast cancer (hazard ratio, 0.26; 95% confidence interval, 0.06-1.10; P = 0.067). However, the association between diffuse thyroid uptake and breast cancer recurrence was statistically significant in multivariate analysis with adjustment for several prognostic variables (hazard ratio, 0.19; 95% confidence interval, 0.57-0.62; P = 0.006). Incidental diffuse thyroid uptake related to autoimmune thyroiditis was an independently favorable prognostic factor in advanced breast cancer. These findings support evidence that thyroid autoimmunity has a beneficial effect on the outcomes of breast cancer patients.