Thyrotropin Receptor Autoantibody Research Articles

Are there any indicative signs in colour Doppler imaging of de novo development thyroid orbitopathy after radioiodine treatment

Aims/Purpose: The aim of this study was to identify indicative signs in doppler flow parameters in the central retinal artery (CRA) and ophthalmic artery (OA) which might be associated with de novo development of thyroid‐associated orbitopathy in the early period after radioiodine treatment in patients with Graves disease.Methods: 82 patients with hyperthyroidism were enrolled: 44 with Graves disease and 38 with toxic nodular goitre. In both groups, blood flow parameters in the CRA and OA were analysed before and 2 and 4 weeks after radioiodine administration. The peak systolic velocity (PSV) and end‐diastolic velocity (EDV) were evaluated, and the resistive index (RI) was calculated.Results: There were no statistically significant differences in the PSV, EDV or RI between groups at baseline and 4 weeks after radioiodine administration. Two weeks after radioiodine administration, the RI in the CRA and EDV in the OA were significantly lower, and the EDV in the CRA was higher in patients with Graves disease than in patients with toxic nodular goitre. There was an inverse correlation between baseline thyrotropin receptor autoantibody (TRAb) levels and the difference between the RI at weeks 4 and 2 (RI3‐RI2) in the CRA and a positive correlation between the baseline anti‐thyroid peroxidase antibody concentration and RI3‐RI2 in the OA.Conclusions: Administration of radioiodine results in more prominent features of hyperkinetic circulation. Patients with Graves disease and high TRAb titers have a lower sensitivity to radioiodine treatment. High TRAb titers suggest higher disease activity and a weaker therapeutic effect of radioiodine.

Thyrotropin receptor autoantibody (TRAb) enhance the expression of thyrotropin receptor on mouse brain vascular endothelial cells: in vivo and in vitro.

The possibility that thyrotropin receptor (TSHR) expression in non-thyroid tissue is well-documented. However, there is insufficient data on the expression of TSHR in medulla oblongata regions, particularly when focusing on the background of encephalopathy associated with hyperthyroidism. In this study, we explored the expression of the functional TSHR in Graves' disease (GD) mouse cerebral vascular endothelial cells and the effects of thyrotropin receptor autoantibody (TRAb) on its expression. A mouse model of GD was constructed with an adenovirus overexpressing TSHR289. The location and expression of the TSHR gene and protein in vivo were determined via RT-qPCR, Western blot, and immunofluorescence techniques. The effect of TRAb on the expression of functional TSHR in vitro was investigated using bEnd.3 cells. Our results show that medulla oblongata vascular endothelial cells from GD mice expressed higher levels of TSHR compared to control mice. In an in vitro experiment, novel results demonstrated that after treatment with a monoclonal TSHR-specific agonistic antibody (M22), the expression of TSHR on the bEnd.3 cells increased at both the protein and mRNA levels. Furthermore, compared with bEnd.3 cells were treated with IBMX only, those treated with M22 showed increased cAMP production. This study suggested that TSHR is expressed and functionally active in the mouse medulla oblongata and in vitro-cultured bEnd.3 cells and TRAb (M22) increased the expression of TSHR on bEnd.3 cells.

Epstein-Barr virus reactivation in peripheral B lymphocytes induces IgM-type thyrotropin receptor autoantibody production in patients with Graves' disease.

Epstein-Barr virus (EBV) is a human herpes virus that latently infects B lymphocytes. When EBV is reactivated, host B cells differentiate into plasma cells and produce IgM-dominant antibodies as well as many progeny virions. The aims of the present study were to confirm the IgM dominance of thyrotropin-receptor antibodies (TRAbs) produced by EBV reactivation and investigate the roles of TRAb-IgM in Graves' disease. Peripheral blood mononuclear cells (PBMCs) containing TRAb-producing cells were stimulated for EBV reactivation, and TRAb-IgM and TRAb-IgG were measured by ELISA. TRAb-IgM were purified and TSH-binding inhibitory activities were assessed using a radio-receptor assay. Porcine thyroid follicular epithelial cells were cultured with TRAb-IgM and/or complements to measure the intracellular levels of cAMP and the amount of LDH released. TRAb-IgM/TRAb-IgG (the MG ratio) was examined in sequential serum samples of Graves' disease and compared among groups of thyroid function. The results obtained showed that IgM-dominant TRAb production was induced by EBV reactivation. TRAb-IgM did not inhibit TSH binding to TSH receptors and did not transduce hormone-producing signals. However, it destroyed thyroid follicular epithelial cells with complements. The MG ratio was significantly higher in samples of hyperthyroidism or hypothyroidism than in those with normal function or in healthy controls. A close relationship was observed between TRAb-IgM produced by EBV reactivation and the development and exacerbation of Graves' disease. The present results provide novel insights for the development of prophylaxis and therapeutics for Graves' disease.

Choroidal structural evaluation in inactive Graves’ ophthalmopathy

PurposeTo investigate the changes in the choroidal structure in patients with inactive Graves Ophthalmopathy (GO). DesignA prospective, masked, observational cross-sectional study. MethodsChanges in choroidal vascularity index (CVI) were studied in the patients with inactive GO using binarization on enhanced depth imaging optical coherence tomography (EDI-OCT) images. Choroidal area, subfoveal choroidal thickness (SFCT), stromal area, luminal area, CVI and retinal nerve fiber layer (RNFL) thickness was used to compare the eyes of sixty-four age-, gender-matched healthy subjects. All measurements were done separately both subfoveal (1500 µm) and total choroidal area (7500 µm). The relation between CVI or SFCT and age, gender, duration of disease, the severity of disease, TRAb (thyrotropin receptor autoantibody), smoking status, and exophthalmometer readings were evaluated. ResultsThere were 56 patients (30 female, 26 male; mean age: 39.5 ± 11.4 years) in the GO group and 64 patients (34 female, 30 male; mean age: 42.2 ± 5.6 years) in the healthy subject group. There was no statistically significant difference between subjects with GO and healthy controls regarding age (p = 0.24) and gender distribution (p = 0.55). Patients with GO had significantly higher intraocular pressure (p = 0.001) and exophthalmometer readings (p = 0.0001) than the healthy controls. The SFCT, CVI1500 and the stromal area1500 was significantly different between the groups (p = 0.009, p = 0.009, p = 0.011, respectively). Multivariate analysis showed that age (-0.871, p = 0.02) was highly correlated with the decreased SFCT, and duration of disease (0.524, p = 0.001) was significantly positively correlated with SFCT. Luminal area1500 (-0.416, p = 0.0001)and stromal area1500 (-0.657, p = 0.0001) were significantly negatively correlated with CVI1500 in the patients with GO. ConclusionAlthough higher CVI1500 was observed in GO patients than in healthy controls, the degree of increase was not the same in the CVI7500. Age and duration of disease significantly affect the SFCT, and luminal area1500 and stromal area1500 significantly affect the CVI1500.

Characterization of Apparently Paradoxical Thyrotropin Binding Inhibitory Immunoglobulins With Neutral Bioactivity.

ContextThe thyrotropin (TSH) receptor (TSH-R) autoantibody activity is clinically measured by inhibition of labeled ligand (TSH or M22) binding to the TSH-R (TSH-binding inhibitory immunoglobulin [TBII]) or by stimulation (TSH-R stimulating antibody [TSAb]) or inhibition (TSH-R blocking antibody [TSBAb]) of 3′,5′-cyclic adenosine 5′-monophosphate (cAMP) production in isolated cells.ObjectiveWe experienced a patient with hypothyroid Graves disease (GD) having strong positive TBII but with almost neutral bioactivities on the TSH-R. The aim of this study is the characterization of this apparently paradoxical TBII (serum sample S).MethodsWe first compared the TBII, TSAb, and TSBAb activities of serum sample S with mixtures of stimulating (S-mAb) and blocking monoclonal Ab (B-mAb). Next, we serially measured cAMPs stimulated by various serum samples in the presence or absence of TSH.ResultsMixtures of S-mAb and B-mAb did not reproduce the characteristics of serum sample S. Instead, serum sample S had a unique feature that blocked the TSH-stimulated cAMP initially but disappeared the blocking activity thereafter to reach the control level.ConclusionWe present here the TBIIs with neutral bioactivities found in the patient with autoimmune thyroid disease, which strongly inhibit TSH binding to the TSH-R but exerts neither TSAb nor TSBAb activity. Differences in the methods of detecting TRAb between TBII in vitro and bioassay may cause the discrepancy. Although serum sample S may be an extreme example, a variety of TRAb that not only stimulates or blocks but also interferes with TSH-R binding for only a short time may exist in the serum samples of GD patients.

Risk factors for Graves' Orbitopathy in surgical patients-Results of a 10-year retrospective study with review of the literature.

IntroductionWe investigated known (eg age, smoking, thyrotropin receptor autoantibody (TRAb)) and new risk factors (eg thyroid peroxidase autoantibodies (TPO‐Ab), thyroid size, or BMI) for Graves' disease (GD) and Graves' orbitopathy (GO), especially in combination with each other, to determine which factors play the most important role in the development of GO.MethodsFrom 2008 to 2018, n = 500 patients with GD were included in this retrospective single‐centre case‐control study. N = 231 (46%) had a GO and n = 269 (54%) showed no GO. Differences in risk factors were determined by Mann‐Whitney U and chi‐square test. Combined influences of factors were examined by multivariable logistic regression.ResultsAge at first diagnosis of GD (OR = 1.043, p < .006), smoking status (OR = 2.64, p < .026) and TRAb (OR = 1.046, p < .01) had a significant impact on GO. The factors gender, TPO‐Ab titre, BMI, TSH titre, T3 and T4 were not significant.ConclusionAs it has been shown in univariate analyses, smoking, age and TRAb levels have a negative impact on the onset and course of GD and GO. Via multivariable regression, we could additionally show that smoking is the most important factor out of those analysed. TRAb might be a helpful surrogate parameter in the assessment of the progress of GO and therefore might be one factor in the decision‐making process for potential early operative surgery. With regard to the hitherto unclear role of BMI, thyroid size and TPO‐Ab in the course of GO, this study could not find any clinically relevant influence.

Immunoglobulin Preparations Can Mislead Clinical Decision-Making in Follow-Up of Differentiated Thyroid Cancer

Objective: Intravenous and subcutaneous immunoglobulins are commonly used for immune substitution or as immune modulators in a variety of inflammatory and autoimmune disorders. Exogenous thyroid-specific thyroglobulin (Tg) antibodies present in the donor plasma may interfere with the interpretation of measurements of Tg autoantibodies (Tg-Abs) in the recipient’s plasma and potentially trigger an immune response in the recipient’s immune cells. Levels of antibodies causing bioassay interferences or those leading to clinically relevant changes in patient outcomes are not known. Tg is used as a biomarker in the long-term surveillance of patients with differentiated thyroid cancer (DTC) following total thyroidectomy and radioactive iodine ablation. However, the presence of Tg-Abs in the circulation interferes with Tg measurements. Assessment of levels of Tg-Abs is thus recommended as a part of standard follow-up of DTC together with Tg testing.Methods: To understand the potential mechanisms and pathophysiologic significance of possible interferences associated with administration immunoglobulin preparations and Tg measurement, we overview the current knowledge on interactions between Tg autoimmunity and immunoglobulin preparations and illustrate diagnostic challenges and perspectives for follow-up of patients with DTC treated with exogenous immunoglobulins.Results: In patients with DTC treated with immunoglobulin preparations, monitoring of thyroid cancer using Tg and Tg-Abs is challenging due to possible analytical interferences through passive transfer of exogenous antibodies from immunoglobulin preparations.Conclusion: Analytical interferences must be suspected when a discrepancy exists between clinical examination and diagnostic tests. Collaboration between endocrinologists, biologists, and pharmacologists is fundamental to avoid misdiagnosis and unnecessary medical or radiologic procedures.Abbreviations: CT = computed tomography; DTC = differentiated thyroid cancer; FNAB = fine-needle aspiration biopsy; HAb = heterophile antibody; IMA = immunometric assay; IVIg = intravenous immunoglobulin; RAI = radioactive iodine; RIA = radioimmunoassay; SCIg = subcutaneous immunoglobulin; Tg = thyroglobulin; Tg-Ab = thyroglobulin autoantibody; Tg-MS = thyroglobulin mass spectrometry; TPO-Ab = thyroid peroxidase autoantibody; TSHR-Ab = thyrotropin receptor autoantibody

Impact of Radioiodine Treatment on Doppler Flow Parameters in the Central Retinal Artery and Ophthalmic Artery in Patients With Hyperthyroidism.

The aim of this study was to identify changes in Doppler flow parameters in the central retinal artery (CRA) and ophthalmic artery (OA) that could be indicative of de novo development of thyroid-associated orbitopathy in the early period after radioiodine treatment. Eighty-two patients with hyperthyroidism were enrolled: 44 with Graves disease and 38 with toxic nodular goiter. In both groups, blood flow parameters in the CRA and OA were analyzed before and 2 and 4 weeks after radioiodine administration. The peak systolic velocity and end-diastolic velocity (EDV) were evaluated, and the resistive index (RI) was calculated. There were no statistically significant differences in the peak systolic velocity, EDV or RI between groups at baseline and 4 weeks after radioiodine administration. Two weeks after radioiodine administration, the RI in the CRA (P = .034) and EDV in the OA (P = .026) were significantly lower, and the EDV in the CRA (P = .004) was higher in patients with Graves disease than in patients with toxic nodular goiter. There was an inverse correlation between baseline thyrotropin receptor autoantibody (TRAb) levels and the difference between the RI at weeks 4 and 2 (RI3-RI2) in the CRA (r = -0.458; P < .05) and a positive correlation between the baseline anti-thyroid peroxidase antibody concentration and RI3-RI2 in the OA (r = 0.435; P < .05). Administration of radioiodine results in more prominent features of hyperkinetic circulation. Patients with Graves disease and high TRAb titers have a lower sensitivity to radioiodine treatment. High TRAb titers suggest higher disease activity and a weaker therapeutic effect of radioiodine.

The Potential Link between Gut Microbiota and Serum TRAb in Chinese Patients with Severe and Active Graves' Orbitopathy.

Background and Objective A previous study reported alterations in the intestinal microbiota in patients with Graves' orbitopathy (GO). Thyrotropin receptor autoantibody (TRAb) stimulates orbital and periorbital tissues and plays a pivotal role in the development of GO. However, the association between gut microbiota and TRAb in GO patients has still remained elusive. In this study, we explored the relationships between gut microbiota and GO-related traits, in which we applied a metabolic-network-driven analysis to identify GO trait-related modules and extracted significant operational taxonomic units (OTUs). Methods In the present study, we profiled gut microbiota using 16S rRNA gene sequencing in 31 GO patients. We performed metabolic-network-driven analysis to investigate the association between gut microbiota and GO-related traits (e.g., TRAb, TGAb, and TPOAb) in the combination of microbial effects. Results Applying microbiome network analysis of cooccurrence patterns and analysis of topological properties, we found that s_Prevotella_copri and f_Prevotellaceae showed a significant correlation with TRAb. In particular, we applied the latent class model to explore the association between gut microbiota and GO-related traits in the combination of microbial effects. It was revealed that the subjects involved in the latent class model with the higher abundance of s_Prevotella_copri and g_Bacteroides had a higher TRAb level. Conclusions Our results revealed the potential relationships between gut microbiota and GO-related traits in the combination of microbial effects. This study may provide a new insight into the interaction between the intestinal microbiota and TRAb-associated immune responses in GO patients.

Superb Microvascular Imaging in the Evaluation of Pediatric Graves Disease and Hashimoto Thyroiditis.

We aimed to investigate the differences between spectral Doppler and Superb Microvascular Imaging (SMI; Canon Medical Systems, Tokyo, Japan) findings in children with Hashimoto thyroiditis (HT) and Graves disease (GD) compared to healthy control participants. The study included 34 patients with GD, 37 patients with HT, and 22 healthy volunteers. All patients with HT and 11 patients with GD were euthyroid; 23 patients with GD had symptoms of hyperthyroidism and had thyrotropin values of less than 0.5 mIU/L. Thyroid volumes, mean resistive indices, and peak systolic velocities along with vascularity indices (VIs) on Superb Microvascular Imaging were measured. Patients with GD had a significantly higher mean thyroid volume (P < .001; right lobe, 11.80 mL; left lobe, 9.10 mL) and peak systolic velocity (right, 32.5 cm/s; left, 30 cm/s) with a lower resistive index (right, 0.48%; left, 0.48%) compared to patients with HT (right, 8.78 mL, 20 cm/s, 0.55%; left, 7.41 mL, 20 cm/s, 0.55%, respectively) and also control participants (right, 4.59 mL, 15 cm/s, 0.56%; left, 3.52 mL, 15 cm/s, 0.54%). Patients with GD had a significantly higher median VI (right, 25%; left, 26%) compared to patients with HT (right, 11%; left, 13%) and control participants (right, 8%; left, 8%). When patients with GD were categorized as euthyroid and hyperthyroid based on thyrotropin levels and clinical symptoms, both euthyroid and hyperthyroid patients with GD had significantly higher thyroid volumes compared to patients with HT (P < .001). Hyperthyroid patients with GD had higher thyroid volumes compared to euthyroid patients with GD; however, the difference failed to reach statistical significance. A significant strong positive correlation with the VI and thyrotropin receptor autoantibody levels (r = 0.696) was found. The highest area under the curve was obtained for the right lobe VI (0.885), followed by the left lobe VI (0.872), right lobe volume (0.828), and peak systolic velocity (0.810). The optimal cutoff VI value for distinguishing between HT and GD was 17.35% with sensitivity, specificity, and diagnostic accuracy of 85.3%, 78.4%, and 81.7%, respectively. Superb Microvascular Imaging is a new method that can detect subtle vascularity changes with higher accuracy compared to spectral Doppler parameters in distinguishing between HT and GD.

OR19-6 A Novel Anti-CD40 Monoclonal Antibody, Iscalimab, Successfully Treats Graves’ Hyperthyroidism

Objective: Graves’ disease (GD) is an autoimmune disorder characterized by thyrotropin receptor autoantibody (TSHR-Ab)-mediated pathology, leading to hyperthyroidism. To date there is no pharmacotherapy that addresses the underlying pathogenesis. The CD40-CD154 (CD40L) co-stimulatory pathway plays an important role in the pathogenesis of GD by promoting auto-reactive B cell activation and intrathyroidal ectopic lymphoid structure formation and function. Iscalimab (CFZ533) is a fully human, blocking and non-depleting anti-CD40 monoclonal antibody. The purpose of this study was to investigate the efficacy and safety of Iscalimab in patients with Graves’ hyperthyroidism. Methods: In total, fifteen patients with Graves’ hyperthyroidism were enrolled in an open label Phase I proof-of concept study and all completed the trial. Each patient received five doses of Iscalimab at 10 mg/kg IV over 12 weeks. We assessed the effects of Iscalimab on thyroid-related hormones (baseline TSH, free and total T3/T4) and autoantibodies (TSHR-Ab) over 36 weeks following the first dose of Iscalimab. Safety, pharmacokinetics, soluble CD40 levels in plasma, free CD40 on whole blood CD19-positive B cells, and CXCL13 were also assessed. Results: Based on the CD40 occupancy and plasma levels of soluble CD40, the intervention resulted in full CD40 engagement for up to 20 weeks (12-week treatment + 8 week follow up). A clinical response and biochemical euthyroidism was observed in seven out of 15 (46.7%) by Day 211. Free T3/T4 normalized in seven (46.7%) patients who did not received any rescue medication with anti-thyroid drugs. Two further patients (13.3%) did not normalize but did not require rescue medication. In contrast, six (40%) patients required rescue medication with anti-thyroid drugs by Day 141. No patients achieved normalization of TSH by Day 85, however, two out of 15 patients (13.3%) showed normal TSH by Day 169. The levels of free thyroid hormones and TSHR-Ab levels declined over time up to Day 211. The mean levels of TSHR-Ab declined from 15.3 IU/L (baseline) to 9.4 IU/L at Day 85 (35% reduction, P<0.001), then further decreased to 4.0 IU/L at day 141 (66% reduction, P<0.001). The TSHR-Ab levels fell in normal range in four out of 15 patients (26.7%). Treatment with Iscalimab was associated with a rapid and significant reduction in the serum levels of CXCL13 (94.1 pg/mL at baseline to 68.5 pg/mL at Day 15) and remained at similar levels during the 12 week treatment period. Twelve patients reported at least one adverse event. Most events were mild in nature (34 in 8 patients, 53.3%) and few were moderate (5 in 4 patients, 26.7%). Conclusions: Iscalimab was generally safe and clinically effective in a subgroup of patients with Graves’ hyperthyroidism. These encouraging results suggest that Iscalimab may be an attractive strategy as the immunomodulation treatment for GD.

Production of thyrotropin receptor antibodies in acute phase of infectious mononucleosis due to Epstein-Barr virus primary infection: a case report of a child.

Various autoantibodies have been reported to be detected during the progression of infectious mononucleosis. We observed a case of infectious mononucleosis due to Epstein–Barr virus primary infection for 2 months, and noticed the transiently increased titer of thyrotropin receptor autoantibodies detected at the acute phase on the 3rd day after admission. At that time, real-time quantitative PCR also revealed the mRNA expressions of an immediate early lytic gene, BZLF1, and a latent gene, EBNA2. The expression of BZLF1 mRNA means that Epstein–Barr virus infects lytically, and EBNA2 protein has an important role in antibody production as well as the establishment of Epstein–Barr virus latency. These results suggest that Epstein–Barr virus lytic infection is relevant to thyrotropin receptor autoantibody production. Thyrotropin receptor autoantibodies stimulate thyroid follicular cells to produce excessive thyroid hormones and cause Graves’ disease. Recently, we reported the thyrotropin receptor autoantibody production from thyrotropin receptor autoantibody-predisposed Epstein–Barr virus-infected B cells by the induction of Epstein–Barr virus lytic infection in vitro. This case showed in vivo findings consistent with our previous reports, and is important to consider the pathophysiology of Graves’ disease and one of the mechanisms of autoimmunity.

Characterization and clinical relevance of circulating CD4+CD28− T cells in Graves’ disease

During autoimmune disease the fraction of CD4+CD28− T cells in the peripheral blood of has been found to be elevated. In the present study, peripheral blood was collected from 61 patients with Graves’ disease (GD) and 30 healthy control participants. Serum concentrations of thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), free thyroxine (FT4) and thyrotropin receptor autoantibody (TRAb) were measured and peripheral blood mononuclear cell (PBMC) surface expression of CD4 and CD28 molecules was detected by flow cytometry. CD4+CD28− cells were sorted from six patients undergoing subtotal thyroidectomy and cultured ex vivo. The influence of TSH pretreated thyroid follicular cells on CD4+CD28− cell proliferation was evaluated using the agonist CD40 mAb 5C11, the blocking CD40L mAb 4F1 or B7-1 mAb 4E5 in 3H-TdR assays. Our data showed that the fraction of CD4+CD28− T cells was higher in GD patients than healthy donors (10.21%±8.56% vs. 2.33%±1.94%; P<0.001), and further elevated in 24 of 61 patients with Graves’ ophthalmopathy (GO) (7.00±6.57% vs. 15.21±8.96%; P<0.001). A higher proportion of CD4+CD28− cells was detected in patients with degree II or III goiter than those with degree I goiter (11.53±9.18% vs. 6.11±3.97%; P<0.05 and 14.50±10.41% vs. 6.11±3.97%; P<0.01). The percentage of CD4+CD28− T cells correlated positively with serum levels of FT3 (r=0.354, P<0.01) and TRAb (r=0.304, P<0.05), but did not correlate with serum FT4 or TSH. Ex vivo, 5C11 enhanced proliferation of CD4+CD28+ cells (P<0.05), but did not influence the proliferation of CD4+CD28− cells. 4F1 inhibited the proliferation of both CD4+CD28+ (P<0.05) and CD4+CD28− (P<0.01) cells, and 4E5 inhibited proliferation of CD4+CD28+ cells (P<0.05). The elevation in circulating CD4+CD28− cells in GD patients correlates with disease severity and maybe plays an important role in the pathogenesis of GD.

The Frequency and Spectrum of Thymus 2-[Fluorine-18] Fluoro-2-deoxy-D-glucose Uptake Patterns in Hyperthyroidism Patients

Thymic hyperplasia is associated with hyperthyroidism. Increased thymus 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) uptake in hyperthyroidism patients has been reported. The aim of this study was to analyze the FDG positron emission tomography (PET) thymus uptake spectrum in patients with active hyperthyroidism with correlation with serum hormones. The prospective study included FDG PET scans from 65 hyperthyroidism patients and 30 subjects with euthyroid status as control group. The intensity of FDG uptake in thyroid and thymus regions was graded subjectively on a five-point scale and semi-quantitatively by measuring standard uptake value (SUV). Correlation coefficient between thymus SUV and serum thyroxine, triiodothyronine, thyrotropin, thyroid peroxidase antibodies (TPO Ab), thyrotropin receptor autoantibody (TR Ab), and thymulin were analyzed. Among 65 hyperthyroidism patients, 30 (46.2%) and 39 (60%) patients showed thyroid and thymus FDG uptake, respectively. The frequency of thymus uptake FDG was high in patients younger than age 40 (28/31, 90.3%). The patterns of the thymic FDG uptake include inverted V or triangular, separated triangular, united nontriangular, unilateral right or left extension, and focal midline. Focal midline FDG uptake was the most common pattern (15/39, 38.5%). None of the control group showed thymus FDG uptake. The correlation coefficient between the FDG uptake SUV levels in thymus and serum hormones, thyrotropin, TPO Ab, TR Ab, and thymulin levels were all low (P > .05). In FDG PET scan, thymus activity was common in hyperthyroidism patients; this should not be misdiagnosed as a malignancy in patients exhibiting weight loss.

Clinical implications of thyrotropin receptor antibody measurement

It has been 50 years since the discovery of thyrotropin receptor autoantibody (TRAb). Advances in the knowledge of thyrotropin receptor ( TSHR) structure and function, combined with the elucidation of TSHR signaling and TSHR-autoantibody interaction have greatly facilitated our understanding of TRAb and their clinical applications. Measurement of TRAb activity plays an important role in the diagnosis of Graves' disease ( GD) and Graves' opthalmopathy. It has also been well recognized that TRAb is an effective predictor of GD relapse or remission after antithyroid drug and radioactive iodine treatment. TRAb test is of particular help in pregnant women and lactating mothers with recent iodine load, where radioactive iodine or technetium tests are contraindicated. In addition, it is useful in the diagnosis and differential diagnosis of fetal and neonatal hyperthyroidism as well as some rare forms of thyrotoxicosis in clinical practice. Accumulating evidence also indicates the possible correlation between thyroid cancer occurring in GD patients with positive TRAb and adverse outcomes. However, further innovation and standardization of TRAb tests are required to help pave the way for clinical applications. Key words: Thyrotropin; Thyrotropin receptor antibody; Graves'disease; Methodology

Hyperthyroidism-Associated Insulin Resistance Is Not Mediated by Adiponectin Levels

To evaluate the relationship between circulating adiponectin and insulin sensitivity in patients with hyperthyroid Graves' disease, we studied 19 adult patients with this disease and 19 age- and sex-matched euthyroid controls. All hyperthyroid patients were treated with antithyroid drugs and were re-evaluated after thyroid function normalized. Before antithyroid treatment, the adiponectin plasma concentrations were not different comparing with those in control group. The adiponectin levels remained unchanged after treatment. The homeostasis model assessment of insulin resistance (HOMA-IR) in hyperthyroid group was higher before treatment than after treatment. There was no significant difference in serum glucose and insulin levels between hyperthyroid and control groups and in the hyperthyroid group before and after treatment. BMI-adjusted adiponectin levels were not different among three groups. On the other hand, BMI-adjusted insulin levels and HOMA-IR values were significantly decreased after management of hyperthyroidism. Pearson's correlation revealed that insulin and HOMA-IR values positively correlated with triiodothyronine (T3) and free thyroxine (FT4) levels. However, adiponectin did not correlate with T3, FT4, insulin, HOMA-IR and thyrotropin receptor autoantibody (TRAb) levels. In conclusion, insulin resistance associated with hyperthyroidism is not mediated by the levels of plasma adiponectin.

Thyrotropin receptor autoantibody measurement following radiometabolic treatment of hyperthyroidism: Comparison between different methods

TSH receptor antibodies (TRAb) play a crucial role in the pathogenesis of Graves' disease (GD). The use of human recombinant TSH-receptor far improved the analytical performance of TRAb assays (2nd-generation assays). The 3rd-generation assay is based on the inhibition of binding of a human biotin-labeled monoclonal thyroid- stimulating antibody (M22) to TSH-receptor by the autoantibodies present in the serum. We aimed to assess the ability of the 2nd- and 3rd-generation assays to detect serum TRAb following radioiodine therapy for hyperthyroidism. Sera from 47 hyperthyroid (25 autoimmune, 22 non-autoimmune) patients were tested using the two different assays before and at different time intervals after radioiodine therapy. The modifications of TRAb were evaluated, as well as the correlation between the two methods. The results obtained by the two methods proved to be closely correlated. A rise in TRAb was invariably observed in GD patients following radioiodine, with a median peak at 6 months, irrespective of their initial clinical status, presence of ophthalmopathy, smoking habits or other variables. Such a rise was nearly superimposable using both methods. No TRAb appearance was observed in patients with non-autoimmune hyperthyroidism. The use of methods of higher sensitivity with respect to that formerly used indicate that nearly all GD patients develop TRAb following radioiodine, and that this phenomenon is transient and not related to baseline conditions and clinical outcome/efficacy of treatment.

A direct binding assay for thyrotropin receptor autoantibodies.

There is, at present, no assay in clinical use for the direct assay of autoantibody binding to the thyrotropin receptor (TSHR). We now describe a direct thyrotropin receptor autoantibody binding assay (DTAb) using a secreted form of the TSHR ectodomain (TSHR-289) without the need for antigen purification. The assay compensates for the low TSHR autoantibody concentration in serum by capturing a relatively large amount of patient immunoglobulin G (IgG) on high-capacity beads, a reversal of standard methods that typically first immobilize antigen. TSHR-289 captured by Graves' IgG was detected in a colorimetric reaction using a biotinylated murine monoclonal antibody to the poly-histidine tail engineered into the antigen. By this approach, sera from 11 normal individuals provided a mean optical density (OD) value of 0.20 +/- 0.08 SD (range 0.06-0.33). Of 38 sera from unselected patients with a history of Graves' disease (untreated and treated), 29 (76%) generated OD values > 0.37 (2 SD above the mean for the normal sera), the highest being OD 1.38. Surprisingly, 3 of 13 (23%) sera from TPO autoantibody-positive patients with Hashimoto's thyroiditis also provided values > 2 SD above the normal sera. The extent of direct autoantibody binding to the TSHR correlated closely with the thyrotropin binding inhibition (TBI) values (r = 0.881; p < 0.001). One serum was clearly positive in only the direct binding assay and another in only the TBI assay. The data obtained with the direct binding assay correlated less well with the thyroid-stimulating antibody (TSAb) assay (r = 0.582; p < 0.001). In summary, we describe a new direct DTAb assay that correlates more closely with the TBI than with the TSI assays. Future studies in a large series of clinically defined patients will be needed to evaluate the clinical utility of the DTAb assay.

Direct Binding of Thyrotropin Receptor Autoantibody toIn VitroTranslated Thyrotropin Receptor: A Comparison to Radioreceptor Assay and Thyroid Stimulating Bioassay

Graves' disease is characterized by the presence of autoantibodies to the thyrotropin receptor (TSHR), which are pathogenic and responsible for disease activity. It is well recognized that the autoantibodies are heterogeneous and recognize a number of different conformational dependent epitopes on the TSHR. In this study, we have extended our previous observations to study the interaction of Graves' disease autoantibodies with TSHR ectodomain produced by in vitro transcription and translation reaction. The specific activity of the translated TSHR ectodomain has been increased by a log fold by adding an efficient ribosome binding Kozak sequence before the translation initiation codon as well as double labelling with 35S-methionine and 35S-cysteine during the translation reaction. Addition of canine pancreatic microsomes to the translation mix showed that the glycosylation of TSHR ectodomain did not occur efficiently for the nascent receptor protein. In order to determine the specificity and sensitivity of the improved assay with nonglycosylated TSHR ectodomain, we have studied 331 sera from Graves' disease patients and as controls 100 sera from patients with nonthyroid autoimmune disorders as well as sera from 200 normal control subjects with no family history of thyroid autoimmunity. With this large cohort of sera from Graves' disease and control individuals, 25% of Graves' disease sera immunoprecipitated the dual labeled, in vitro transcribed and translated TSHR ectodomain, exceeding the 98th percentile of the control sera. There was no correlation between the autoantibodies that immunoprecipitate the in vitro translated TSHR ectodomain and those that inhibit iodinated TSH binding in the radioreceptor assay and those with biological activity in a bioassay. The data are consistent with the finding that a proportion of Graves' disease autoantibodies can interact directly with TSHR ectodomain produced by in vitro transcription and translation. However, in contrast to the wide use of similar translation and immunoprecipitation assays to measure other autoantibodies for the diagnosis of autoimmune disorders, such as type 1 diabetes, the TSHR immunoprecipitation on its own is unsuitable for diagnosis of Graves' disease.