A novel bioassay for anti-thyrotrophin receptor autoantibodies detects both thyroid-blocking and stimulating activity

Development and basic performance verification of a rapid homogeneous bioassay for agonistic antibodies against the thyroid-stimulating hormone receptor

Graves' disease is a type of autoimmune hyperthyroidism caused by thyroid-stimulating antibodies (TSAb).1 The combination of a porcine thyroid cell bioassay and cyclic adenosine monophosphate (cAMP) immunoassay (TSAb-enzyme immunoassay; EIA) is a clinically approved TSAb measurement method. Due to the requirement of multiple procedures and a long assay time of 6 h in the TSAb-EIA, a simplified and rapid assay is desired. Herein, we developed a rapid homogeneous TSAb bioassay (rapid-TSAb assay) using the human embryonic kidney cell line (HEK293), engineered to express the human thyroid-stimulating hormone receptor (TSHR), along with a cAMP-dependent luminescence biosensor. The measurement consists of three steps: thawing frozen cells, blood sample addition, and luminescence detection. The procedures can be conducted within 1 h. The World Health Organization International Standard TSAb (NIBSC 08/204) stimulated the cells co-expressing TSHR and cAMP biosensor. The intra- and inter-assay coefficients of variance were < 10%. Stimulation activity using wild-type TSHR and chimeric TSHR (Mc4) almost completely correlated with the tested Graves' disease and normal samples. In the rapid-TSAb assay, the evaluation of 39 samples, including TSHR antibody-positive sera, yielded a sensitivity of 100.0% and a specificity of 90.9%, compared to the TSAb-EIA control. The rapid-TSAb assay enables simple and rapid measurement of TSAb and is promising for improving the diagnosis of autoimmune thyroid diseases.

Bioassays for thyrotropin receptor autoantibodies

Bioassays using animal models were essential tools in the discovery of thyrotropin and in enhancing our understanding of the physiology of the pituitary-thyroid axis. These same bioassays were also instrumental in the discovery of autoantibodies to the thyrotropin receptor (TSH-R-Ab) and in identifying their role in the pathophysiology of Graves' disease. The development of cell-based bioassays led to further advances in our knowledge of the functional activity of TSH-R-Ab and to the discovery that TSH-R-Ab can be either thyroid-stimulating or thyroid blocking, and that they occur in other types of autoimmune thyroid diseases (AITD) besides Graves' disease. More recently, TSH-R-Ab bioassays have been advanced from research tools to clinical laboratory tests. Whereas TSH-R-Ab can be measured with competitive-binding immunoassays, these assays do not provide information on the functional activity of TSH-R-Ab. Bioassays, in contrast, can differentiate between the stimulatory or blocking activity of TSH-R-Ab which provides clinically useful information that can inform the management of patients with AITD. The clinical use of TSH-R-Ab bioassays, however, has been limited to-date by their inherent complexity and long turn-around-time. Recent advances in biosensors have been applied to the development of TSH-R-Ab bioassays that are rapid and simple to perform. We now are entering an era in which bioassays for TSH-R-Ab can be measured routinely by virtually any clinical laboratory.

Chemokines in thyroid autoimmunity

The chemokine receptor CXCR3 and its chemokines CXCL9, CXCL10, and CXCL11 are involved in the pathogenesis of autoimmune diseases. Th1 lymphocytes are recruited by Th1 chemokines, secreted by damaged cells. In inflamed tissues, the attracted Th1 lymphocytes induce the IFN-gamma and TNF-alpha release, that stimulates the secretion of Th1 chemokines, initiating and reiterating an amplification feedback loop. Autoimmune thyroid disorders (AITD) are the most recurrent autoimmune diseases, including Graves' disease (GD) and autoimmune thyroiditis, clinically defined by thyrotoxicosis and hypothyroidism, respectively. Graves' ophthalmopathy is one of GD extrathyroidal manifestations, occurring in ~30-50% of GD patients. In the early phase of AITD, the Th1 immune response is prevalent, and a following switch to a Th2 immune response has been shown in the late, inactive, phase. The reviewed data underline the importance of chemokines in thyroid autoimmunity and suggest CXCR3-receptor and its chemokines as potential targets of novel drugs for these disorders.

Characterization of apparently paradoxical thyrotropin binding inhibitory immunoglobulins with neutral bioactivity

Context

The 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.

Objective

We 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).

Methods

We 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.

Results

Mixtures 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.

Conclusion

We 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.

The Prediction Model Using Thyroid Stimulating Immunoglobulin Bioassay For Relapse of Graves’ Disease

Objective

Thyroid-stimulating immunoglobulin (TSI) bioassay has a better ability to predict the relapse rate of Graves’ disease (GD) than the thyroid-stimulating hormone (TSH)-binding inhibitory immunoglobulin method in terms of measuring the TSH receptor antibody. However, the optimal TSI bioassay cutoff for predicting relapse after antithyroid drug (ATD) withdrawal is not well evaluated.

Methods

This retrospective study enrolled GD patients who had been treated with ATD and obtained their TSI bioassay <140% from January 2010 to December 2019 in a referral hospital.

Results

Among 219 study subjects, 86 patients (39.3%) experienced relapse. The TSI bioassay value of 66.5% significantly predicted the relapse of GD (P = 0.049). The group with a TSI bioassay value > 66.5% were expected to show a 23.8% relapse rate at 2 from ATD withdrawal, and the group with a TSI < 66.5% had a 12.7% relapse rate based on Kaplan-Meier curves analysis. The TSI bioassay showed a good ability to predict relapse GD in the female group (P = 0.041) but did not in the male group (P = 0.573). The risk scoring based on the nomogram with risk factors for GD relapse, which was constructed to overcome the limitation, increased the predictive ability of GD relapse by 11.5% compared to the use of the TSI bioassay alone.

Conclusions

The cutoff value of the TSI bioassay to predict GD relapse should be lower than that for diagnosing GD. However, as the single use of the TSI bioassay has limitations, a nomogram with multiple risk factors including TSI bioassay could be helpful to predict GD relapse.

Clinical value of functional thyrotropin receptor antibodies in Serbian patients with Graves' orbitopathy

PURPOSE

Thyrotropin receptor autoantibodies (TSH-R-Ab) are heterogeneous in their biological function and play a significant role in the pathophysiology of both Graves' disease and Graves' orbitopathy (GO). The clinical significance and utility of determining functional TSH-R-Ab in a Serbian collective were evaluated.

METHODS

91 consecutive patients with GO were included in this study. Total TSH-R-Ab concentration, referred to as TSH-R binding inhibitory immunoglobulins (TBII) was detected using a competitive-binding immunoassay. Stimulating and blocking TSH-R-Ab (TSAb and TBAb) were measured with cell-based bioassays.

RESULTS

Stimulating TSAb activity and TBII positivity were detected in 85 of 91 (93.4%) and 65 of 91 (71.4%) patients with GO (P < 0.001). Blocking TBAb activity was observed in only one patient who expressed dual stimulating and blocking TSH-R-Ab activity. The sensitivity rates for differentiating between clinically active versus inactive and mild versus moderate-to-severe GO were 100% and 100% for TSAb, respectively. In contrast, these were 82% and 87% only for TBII. Seven of eight (87.5%) and one of eight (12.5%) euthyroid patients with GO were TSAb and TBII positive, respectively (P < 0.031). TSAb serum levels significantly predicted GO activity compared to TBII (odds ratio, OR, 95%CI: 3.908, 95%CI 1.615-9.457, P = 0.003; versus 2.133, 0.904-5.032, P = 0.084, univariate analysis; and OR 4.341, 95%CI 1.609-11.707, P = 0.004; versus 2.337, 0.889-6.145, P = 0.085 multivariate analysis).

CONCLUSION

Stimulating TSAb are highly prevalent in patients with GO and show superior clinical characteristics and predictive potential compared to the traditionally used TBII.

Effects of vitamin D on thyroid autoimmunity markers in Hashimoto's thyroiditis: systematic review and meta-analysis

OBJECTIVE

To perform a meta-analysis of randomized controlled trials to evaluate the efficacy of vitamin D supplementation on thyroid autoimmunity markers in Hashimoto's thyroiditis (HT).

METHODS

This meta-analysis included randomized controlled clinical trials identified by a systematic search of electronic databases (PubMed®, MEDLINE®, EMBASE, The Cochrane Library, China National Knowledge Infrastructure) from inception to August 2020. All studies included patients with HT that received vitamin D supplementation irrespective of the doses administered or the duration of treatment. The primary and secondary outcome measures were thyroid peroxidase antibody (TPOAb) and/or thyroglobulin antibody (TGAb) titres.

RESULTS

Eight studies (n = 652) were included. There was significant heterogeneity between the studies. Using a random-effect model, vitamin D supplementation reduced TPOAb titre (standardized mean difference [SMD]: -1.11; 95% confidence interval [CI]: 1-1.92, -0.29) and TGAb titre (SMD: -1.12; 95% CI: -1.96, -0.28). A subgroup analysis demonstrated that vitamin D supplementation for >3 months resulted in a decrease in TPOAb titre (SMD: -1.66, 95% CI: -2.91, -0.41) but treatment ≤3 months was ineffective. Treatment with vitamin D₃ decreased TPOAb titre (SMD: -1.48; 95% CI: -2.53, -0.42) whereas vitamin D did not.

CONCLUSION

These data suggest that vitamin D reduces autoantibody titre in patients with HT.

SENSITIVITY OF THREE THYROTROPIN RECEPTOR ANTIBODY ASSAYS IN THYROID-ASSOCIATED ORBITOPATHY

Background

Thyrotropin receptor autoantibodies (TSH-RAb) are indispensable biomarkers in the laboratory assessment of thyroid-associated orbitopathy (TAO). Clinical sensitivity of three different assays for TSH-R-Ab determination was evaluated in patients with TAO.

Methods

87 consecutive TAO patients were enrolled and their serum samples analyzed in parallel with three assays. An ECLIA competitive binding and a chemiluminescent bridge immunoassay were used to measure total and binding TSH-R-Ab concentration, while their functional activity was determined using a stimulatory TSH-R-Ab (TSAb) cellbased bioassay.

Results

Compared to the two binding assays (ECLIA p<0.001, bridge p=0.003), the TSAb bioassay was more sensitive pertaining to the positive detection of TSH-R-Ab in TAO patients. No difference (p=0.057) was noted between the ECLIA and bridge assays regarding sensitivity rate. All patients with active and/or moderate-to-severe TAO tested positive in the TSAb bioassay (100% and 100%, respectively), while the positivity rates for bridge and ECLIA binding assays were 89.7% and 82.1% for active TAO, and 90.2% and 86.3% for severe TAO, respectively. Negative predictive values of the bioassay, bridge, and ECLIA assays were 100%, 75%, and 71%, respectively for active TAO, and 100%, 86%, and 71%, respectively for moderate-to-severe TAO. The superiority of the bioassay was most prominent in euthyroid (ET) TAO. Positivity rates of the TSAb bioassay, bridge and ECLIA binding assays were 89.6%, 75%, and 64.6%, respectively for inactive TAO; 86.1%, 69.4%, and 52.8%, respectively for mild TAO; 87.5%, 62.5%, and 12.5%, respectively for euthyroid TAO. The bridge assay correlated better with the ECLIA binding assay (r=0.893, p<0.001), compared to the bioassay (r=0.669, p<0.001).

Conclusions

In patients with TAO of various activity and severity, the TSAb bioassay demonstrates a superior clinical performance compared to both ECLIA and bridge binding assays.

A rapid homogenous bioassay for detection of thyroid-stimulating antibodies based on a luminescent cyclic AMP biosensor

Graves' disease (GD) is an autoimmune disease caused by antibodies to the thyroid stimulating hormone receptor (TSHR). The FDA-cleared Thyretain™ TSI bioassay is a highly specific method to detect thyroid stimulating antibodies (TSAb/TSI) in the blood of patients with autoimmune thyroid disease (AITD), particularly GD. To simplify the workflow of this bioassay and to support a semi-quantitative result, we have generated a stable CHO-K1 cell line expressing both a chimeric TSH receptor (TSHR-Mc4) and a luciferase-based homogeneous cAMP biosensor (GS luciferase). Here, we describe a rapid, real-time, homogenous bioassay (Turbo™ TSI Bioassay) to directly assess the functional activity of TSI and produce results in International Units of IU/L. The Turbo™ TSI bioassay works by measuring changes in the intracellular cAMP level induced by a G-protein coupled receptor (G-PCR) signaling cascade which is triggered by the binding of TSI to the TSHR. Upon binding to cAMP, the GS luciferase reporter is activated through conformational changes and generates light that can be measured in intact cells with a luminometer. The LoD and LoQ of the assay were determined to be 0.016 IU/L and 0.03 IU/L, respectively and the preliminary assay cutoff was determined to be 0.024 IU/L by ROC analysis using the Thyretain™ TSI bioassay results as reference. The analytical performance of the Turbo™ TSI bioassay is comparable to the Thyretain™ TSI bioassay as evidenced by similar EC₅₀ values for a TSHR stimulating monoclonal antibody (M22). The specificity of the Turbo™ TSI bioassay was demonstrated by showing no response to a high concentration of a human monoclonal TSHR blocking antibody (K1-70). The precision of the assay was excellent with an overall within-laboratory precision <15% CV. When testing 198 clinical samples, the positive and negative percent agreement between the Turbo™ TSI and the Thyretain™ TSI bioassays were 98.7% and 93.5%, respectively. While both bioassays yield equivalent analytical and clinical performances, the Turbo™ TSI bioassay is much simpler to perform. It does not require cell culture, sample dilution, washing or cell lysis steps, resulting in a dramatically reduced turnaround time from about 21 h to 60 min. In addition, the same cell line showed its capability of detecting thyroid blocking antibodies (TBAb/TBI) in a competitive format. The Turbo™ TSI bioassay is user-friendly and is a very promising advancement to aid the diagnosis of autoimmune thyroid disease (AITD).

Blocking the Thyrotropin Receptor with K1-70 in a Patient with Follicular Thyroid Cancer, Graves' Disease, and Graves' Ophthalmopathy

Background: We report the therapeutic use of K1-70™, a thyrotropin receptor (TSHR) antagonist monoclonal antibody, in a patient with follicular thyroid cancer (FTC), Graves' disease (GD), and Graves' ophthalmopathy (GO). Methods: A 51-year-old female patient, who smoked, presented in October 2014 with FTC complicated by GD, high levels of TSHR autoantibodies with high thyroid stimulating antibody (TSAb) activity, and severe GO. K1-70 was administered at 3 weekly intervals with the dose adjusted to block TSAb activity. Her cancer was managed with lenvatinib and radioiodine therapy. Results: Following initiation of K1-70 therapy, TSAb activity measured in serum decreased and GO (proptosis and inflammation) improved. On K1-70 monotherapy during the pause in lenvatinib, several metastatic lesions stabilized while others showed progression attenuation compared with that before lenvatinib therapy. Conclusions: These observations suggest that blocking TSHR stimulation with K1-70 can be an effective treatment for GO and may also benefit select patients with FTC and GD.

A cyclic peptide significantly improves thyroid function, thyrotropin-receptor antibodies and orbital mucine /collagen content in a long-term Graves' disease mouse model

BACKGROUND

BALB/c mice which received long-term immunizations of adenovirus (Ad) expressing thyrotropin receptor A-subunits (TSHR) developed stable Graves' disease (GD). TSHR-derived cyclic peptide 19 (P19) was identified as effective therapy in this model.

METHODS

In Ad-TSHR mice, we investigated shorter disease intervals up to 4 months for histological alterations of the orbits, fine tuning of anti-TSHR antibodies (Ab) and free thyroxine (fT4) hormone levels by using novel detection methods in an independent laboratory. Therapy (0.3 mg/kg P19 or vehicle) was given intravenously after the fourth Ad-TSHR immunization (week 11) and continued until week 19.

RESULTS

Thyrotropin binding inhibitory immunoglobulins (TBII, bridge immunoassay), blocking (TBAb) and stimulating (TSAb) TSHR-Ab (both cell-based bioassays) and serum levels of fT4 were significantly elevated at week 11 in Ad-TSHR-immunized mice versus none in control mice. For the first time, TSAb, TBAb, and thyroperoxidase-Ab were detected in 17 of 19, 12/19 and 6/19 Ad-TSHR immunized mice, respectively at week 21. Also, for the first time, this study showed that P19 treatment markedly reduced serum TBII (p < 0.0001), serum fT4 (p = 0.02), and acidic mucins and collagen content in the orbital tissue of Ad-TSHR-immunized mice.

CONCLUSION

P19 significantly improved thyroid function, confirming previous results in an independent second laboratory. A relevant shift of anti-TSHR antibody subpopulations in response to P19 therapy may help explain its immunological effects. Moreover, P19 exerted a beneficial effect on mucine and collagen content of orbital tissue. Hence, P19 offers a potential novel therapeutic approach for GD and associated orbitopathy.

Thyrotropin receptor antibodies and Graves' orbitopathy

CONTEXT AND PURPOSE

The thyrotropin receptor (TSHR) is the key autoantigen in Graves' disease (GD) and associated orbitopathy (GO). Antibodies targeting the TSHR (TSHR-Ab) impact the pathogenesis and the course of GO. This review discusses the role and clinical relevance of TSHR-Ab in GO.

METHODS

Review of the current and pertinent literature.

RESULTS

GO is the most common extrathyroidal manifestation of GD and is caused by persistent, unregulated stimulation of TSHR-expressing orbital target cells (e.g. fibroblasts and pre-adipocytes). Serum TSHR-Ab and more specifically, the stimulatory Ab (TSAb) are observed in the vast majority of patients with GD and GO. TSHR-Ab are a sensitive serological parameter for the differential diagnosis of GO. TSHR-Ab can be detected either with conventional binding immunoassays that measure binding of Ab to the TSHR or with cell-based bioassays that provide information on their functional activity and potency. Knowledge of the biological activity and not simply the presence or absence of TSHR-Ab has relevant clinical implications e.g. predicting de-novo development or exacerbation of pre-existing GO. TSAb are specific biomarkers of GD/GO and responsible for many of its clinical manifestations. TSAb strongly correlate with the clinical activity and clinical severity of GO. Further, the magnitude of TSAb indicates the onset and acuity of sight-threatening GO (optic neuropathy). Baseline serum values of TSAb and especially dilution analysis of TSAb significantly differentiate between thyroidal GD only versus GD + GO.

CONCLUSION

Measurement of functional TSHR-Ab, especially TSAb, is clinically relevant for the differential diagnosis and management of GO.

Non-Conventional Clinical Uses of TSH Receptor Antibodies: The Case of Chronic Autoimmune Thyroiditis

Anti TSH receptor antibodies (TSHrAb) are a family of antibodies with different activity, some of them stimulating thyroid function (TSAb), others with blocking properties (TBAb), it is a common finding that antibodies with different function might coexist in the same patient and can modulate the function of the thyroid. However, most of the labs routinely detect all antibodies binding to the TSH receptor (TRAb, i.e. TSH-receptor antibodies detected by binding assay without definition of functional property). Classical use of TSHr-Ab assay is in Graves' disease where they are tested for diagnostic and prognostic issues; however, they can be used in specific settings of chronic autoimmune thyroiditis (CAT) as well. Aim of the present paper is to highlight these conditions where detection of TSHr-Ab can be of clinical relevance. Prevalence of TSHrAb is different in in the 2 main form of CAT, i.e. classical Hashimoto's thyroiditis and in atrophic thyroiditis, where TBAb play a major role. Simultaneous presence of both TSAb and TBAb in the serum of the same patient might have clinical implication and cause the shift from hyperthyroidism to hypothyroidism and vice versa. Evaluation of TRAb is recommended in case of patients with Thyroid Associated Orbitopathy not associated with hyperthyroidism. At present, however, the most relevant recommendation for the use of TRAb assay is in patients with CAT secondary to a known agent; in particular, after treatment with alemtuzumab for multiple sclerosis. In conclusion, the routine use of anti-TSH receptor antibodies (either TRAb or TSAb/TBAb) assay cannot be suggested at the present for diagnosis/follow up of patients affected by CAT; there are, however, several conditions where their detection can be clinically relevant.

Type 1 Diabetes and Autoimmune Thyroid Disease-The Genetic Link

Type 1 diabetes (T1D) and autoimmune thyroid disease (AITD) are the most frequent chronic autoimmune diseases worldwide. Several autoimmune endocrine and non-endocrine disorders tend to occur together. T1D and AITD often cluster in individuals and families, seen in the formation of autoimmune polyendocrinopathy (AP). The close relationship between these two diseases is largely explained by sharing a common genetic background. The HLA antigens DQ2 (DQA1*0501-DQB1*0201) and DQ8 (DQA1*0301-DQB1*0302), tightly linked with DR3 and DR4, are the major common genetic predisposition. Moreover, functional single nucleotide polymorphisms (or rare variants) of various genes, such as the cytotoxic T-lymphocyte- associated antigen (CTLA4), the protein tyrosine phosphatase non-receptor type 22 (PTPN22), the interleukin-2 Receptor (IL2Ra), the Vitamin D receptor (VDR), and the tumor-necrosis-factor-α (TNF) that are involved in immune regulation have been identified to confer susceptibility to both T1D and AITD. Other genes including cluster of differentiation 40 (CD40), the forkhead box P3 (FOXP3), the MHC Class I Polypeptide-Related Sequence A (MICA), insulin variable number of tandem repeats (INS-VNTR), the C-Type Lectin Domain Containing 16A (CLEC16A), the Erb-B2 Receptor Tyrosine Kinase 3 (ERBB3) gene, the interferon-induced helicase C domain-containing protein 1 (IFIH1), and various cytokine genes are also under suspicion to increase susceptibility to T1D and AITD. Further, BTB domain and CNC homolog 2 (BACH2), C-C motif chemokine receptor 5 (CCR5), SH2B adaptor protein 3 (SH2B3), and Rac family small GTPase 2 (RAC2) are found to be associated with T1D and AITD by various independent genome wide association studies and overlap in our list, indicating a strong common genetic link for T1D and AITD. As several susceptibility genes and environmental factors contribute to the disease aetiology of both T1D and AITD and/or AP subtype III variant (T1D+AITD) simultaneously, all patients with T1D should be screened for AITD, and vice versa.

A Novel Long-Term Graves' Disease Animal Model Confirmed by Functional Thyrotropin Receptor Antibodies

INTRODUCTION

A novel long-term murine model for Graves' disease (GD) using repeated, long-term immunizations with recombinant adenovirus expressing the extracellular A-subunit of the human thyrotropin receptor (Ad-TSHR) was applied to evaluate the functional anti-TSHR-antibody (TSHR-Ab) profile.

METHODS

BALB/c mice received 7 immunizations with either 10¹⁰ plaque-forming units of Ad-TSHR or control Ad-GFP. Naïve (nonimmuized native) mice were also studied. Three 3-weekly immunizations were followed by 4-weekly boosts until the 7th immunization. Blocking (TBAb) and stimulating (TSAb) TSHR-Ab were measured with bioassays. Assay cut-offs for TBAb/TSAb were at 34% inhibition and a specimen-to-reference ratio (SRR) of 140%.

RESULTS

Nineteen (8 Ad-TSHR-, 4 Ad-GFP-immunized, and 7 native) mice were investigated. All native mice were negative for TSHR-binding inhibitory immunoglobulins (TBII) prior to immunization. Native and Ad-GFP mice were negative in weeks 17 and 27 for TBII and TBAb/TSAb. In native mice, the free thyroxine (fT4) levels (median [25th percentile; 75th percentile]) were in the upper normal range (1.2 ng/mL [1.1; 1.6]) prior to immunization, at weeks 17 (2.2 ng/mL [2.1; 2.4]) and 27 (1.4 ng/mL [1.1; 1.7]), respectively. In contrast, in Ad-TSHR-immunized mice, fT4 values were markedly increased at weeks 17 (4.4 ng/mL [3.9; 6]) and 27 (4.5 ng/mL [4.2; 6]) compared to those in Ad-GFP mice (2 ng/mL [1.8; 2.1] and 1.4 ng/mL [1.1; 1.6]), respectively (p = 0.0008, p = 0.001). In contrast, at week 17, in Ad-TSHR mice, the mean TBII, TBAb, and TSAb levels were 40 IU/L (40; 40); 62% inhibition (38; 69), and 116% SRR (97; 185), respectively; at week 27, they were 40 IU/L (39; 40); 65% inhibition (34; 80) and 95% SRR (63; 187), respectively. Three serum samples from Ad-TSHR mice (38%) demonstrated dual TBAb/TSAb positivity.

CONCLUSIONS

TBAb/TSAb were highly prevalent in Ad-TSHR-immunized mice, thus confirming the successful establishment of a novel, long-term murine model for GD. All TBAb- and TSAb-positive Ad-TSHR-immunized mice were TBII-positive. Thus, the binding immunoassay did not differentiate between TSHR-Ab functionality.

Management of Graves Thyroidal and Extrathyroidal Disease: An Update

CONTEXT

Invited update on the management of systemic autoimmune Graves disease (GD) and associated Graves orbitopathy (GO).

EVIDENCE ACQUISITION

Guidelines, pertinent original articles, systemic reviews, and meta-analyses.

EVIDENCE SYNTHESIS

Thyrotropin receptor antibodies (TSH-R-Abs), foremost the stimulatory TSH-R-Abs, are a specific biomarker for GD. Their measurement assists in the differential diagnosis of hyperthyroidism and offers accurate and rapid diagnosis of GD. Thyroid ultrasound is a sensitive imaging tool for GD. Worldwide, thionamides are the favored treatment (12-18 months) of newly diagnosed GD, with methimazole (MMI) as the preferred drug. Patients with persistently high TSH-R-Abs and/or persistent hyperthyroidism at 18 months, or with a relapse after completing a course of MMI, can opt for a definitive therapy with radioactive iodine (RAI) or total thyroidectomy (TX). Continued long-term, low-dose MMI administration is a valuable and safe alternative. Patient choice, both at initial presentation of GD and at recurrence, should be emphasized. Propylthiouracil is preferred to MMI during the first trimester of pregnancy. TX is best performed by a high-volume thyroid surgeon. RAI should be avoided in GD patients with active GO, especially in smokers. Recently, a promising therapy with an anti-insulin-like growth factor-1 monoclonal antibody for patients with active/severe GO was approved by the Food and Drug Administration. COVID-19 infection is a risk factor for poorly controlled hyperthyroidism, which contributes to the infection-related mortality risk. If GO is not severe, systemic steroid treatment should be postponed during COVID-19 while local treatment and preventive measures are offered.

CONCLUSIONS

A clear trend towards serological diagnosis and medical treatment of GD has emerged.

Type 1 diabetes and associated autoimmune diseases

BACKGROUND

Common autoimmune diseases (AID) tend to occur together in the same individual and families. Type 1 diabetes (T1D) is caused by an autoimmune-induced inflammatory destruction of the pancreatic tissue and clusters with several other AID.

AIM

To compare the demographic, clinical, and serological features of patients with single T1D vs those with T1D and associated AID.

METHODS

From October 1999 to February 2020, a total of 665 patients with T1D and their first-degree relatives were evaluated.

RESULTS

Compared to patients with isolated T1D, those with T1D + AID were older and had a higher female: male ratio. Average patient age and age at disease onset were higher in T1D + AID vs T1D only. The average time interval between T1D onset and the onset of a second glandular AID was markedly shorter than the time interval between T1D and the occurrence of a non-endocrine AID. T1D-specific autoantibodies were more frequent in patients with T1D + AID and relatives vs those with T1D only. However, the prevalence of AID and autoantibodies against various tissues were found to be higher in relatives of patients with T1D only compared to relatives of patients with T1D + AID.

CONCLUSION

Annual serological and subsequent functional screening for AID in patients with T1D and their first-degree relatives is recommended.

Prospective Trial of Functional Thyrotropin Receptor Antibodies in Graves Disease

CONTEXT

Scarce data exist regarding the relevance of stimulatory (TSAb) and blocking (TBAb) thyrotropin receptor antibodies in the management of Graves disease (GD).

OBJECTIVE

To evaluate the clinical utility and predictive value of TSAb/TBAb.

DESIGN

Prospective 2-year trial.

SETTING

Academic tertiary referral center.

PATIENTS

One hundred consecutive, untreated, hyperthyroid GD patients.

METHODS

TSAb was reported as percentage of specimen-to-reference ratio (SRR) (cutoff SRR < 140%). Blocking activity was defined as percent inhibition of luciferase expression relative to induction with bovine thyrotropin (TSH, thyroid stimulating hormone) alone (cutoff > 40% inhibition).

MAIN OUTCOME MEASURES

Response versus nonresponse to a 24-week methimazole (MMI) treatment defined as biochemical euthyroidism versus persistent hyperthyroidism at week 24 and/or relapse at weeks 36, 48, and 96.

RESULTS

Forty-four patients responded to MMI, of whom 43% had Graves orbitopathy (GO), while 56 were nonresponders (66% with GO; P < 0.01). At baseline, undiluted serum TSAb but not thyroid binding inhibitory immunoglobulins (TBII) differentiated between thyroidal GD-only versus GD + GO (P < 0.001). Furthermore, at baseline, responders demonstrated marked differences in diluted TSAb titers compared with nonresponders (P < 0.001). During treatment, serum TSAb levels decreased markedly in responders (P < 0.001) but increased in nonresponders (P < 0.01). In contrast, TBII strongly decreased in nonresponders (P = 0.002). All nonresponders and/or those who relapsed during 72-week follow-up period were TSAb-positive at week 24. A shift from TSAb to TBAb was noted in 8 patients during treatment and/or follow-up and led to remission.

CONCLUSIONS

Serum TSAb levels mirror severity of GD. Their increase during MMI treatment is a marker for ongoing disease activity. TSAb dilution analysis had additional predictive value.

Reply to Drs. Kiaei and Molinaro Regarding the Publication "Comparison of a Bridge Immunoassay with Two Bioassays for Thyrotropin Receptor Antibody Detection and Differentiation"

Dear Editor,Drs. Kiaei and Molinaro 1 put forth two criticisms of the manuscript published by us 2. They state that the experimental design of this study is flawed and that the authors falsely claim that negative Thyretain™ TSI Reporter BioAssay results for two Graves' diseases patients undergoing drug treatments means the absence of stimulating antibodies. To substantiate this claim Drs. Kiaei and Molinaro point out that the manufacturer of the Thyretain TSI Reporter BioAssay clearly states in the package insert that "[t]he effects of various drug therapies on the performance of this Kit have not been established" 1. Second, the package insert explicitly states that "[a] negative result does not exclude the possibility of the presence of TSI" and results of the test should be interpreted in conjunction with information available from other clinical information, such as physical symptoms and thyroid hormone testing, as recommended by the American Thyroid Association (ATA)". Furthermore they state that the "authors of the manuscript did not consider the manufacturer's warning regarding the intended patient population and the ATA guidelines regarding the interpretation of the test results in conjunction with other clinical information. Instead, the authors based their conclusions on the negative Thyretain TSI Reporter BioAssay results and ignored the patients' clinical history of Graves' disease."

Comparison of a Novel Homogeneous Cyclic Amp Assay and a Luciferase Assay for Measuring Stimulating Thyrotropin-Receptor Autoantibodies

OBJECTIVE

Stimulating thyrotropin-receptor antibodies (TSAb) cause Graves' disease (GD). We tested a novel homogeneous fluorescent 3',5' cyclic adenine monophosphate (cAMP) assay for the detection of TSAb in a bioassay.

METHODS

Chinese hamster ovary (CHO) cell lines expressing either a chimeric (MC4) or wild-type (WT) TSH-R were incubated with the adenyl cyclase activator forskolin, a human TSAb monoclonal antibody (M22), and with sera from GD patients. Intracellular cAMP levels were measured using a Bridge-It® cAMP assay, and the results were compared with a luciferase-based bioassay.

RESULTS

Both cell lines were stimulated with forskolin concentrations (0.006-200 µM) in a dose-dependent manner. The linear range in the MC4 and WT cells was 0.8-25 and 3.1-50 µM, respectively. Levels of cAMP and luciferase in forskolin-treated MC4 and WT cells were positively correlated (r = 0.91 and 0.84, both p < 0.001). The 50% maximum stimulatory concentration of forskolin was more than 16-fold higher for the CHO-WT cells than the CHO-MC4 cells in the cAMP assay and 4-fold higher in the luciferase assay. Incubation of both cell lines with M22 (0.006-50 ng/mL) resulted in a dose-dependent increase in cAMP levels with linear ranges for the MC4 and WT cells of 0.8-12.5 and 0.2-3.125 ng/mL, respectively. Comparison of cAMP and luciferase levels in M22-treated MC4 and WT cells also showed a positive correlation (r = 0.88, p < 0.001 and 0.75, p = 0.002). A positive correlation was also noted when using patient samples (r = 0.96, p < 0.001) that were all TSH-R-Ab binding assay positive.

CONCLUSION

The novel, rapid, simple-to-perform cAMP assay provides TSAb-mediated stimulatory results comparable to a luciferase-based bioassay.

Epidemiology, Natural History, Risk Factors, and Prevention of Graves' Orbitopathy

GO is the most frequent extrathyroidal manifestation of Graves' disease, although it may rarely occur in euthyroid/hypothyroid patients with chronic autoimmune thyroiditis. It is a relatively infrequent disorder, and men tend to have more severe ocular involvement at an older age. The prevalence of GO is lower than in the past among patients with recent onset Graves' hyperthyroidism, and moderate-to-severe forms requiring aggressive treatments are no more than 5-6% of all cases of GO. After an initial inflammatory (active) phase and a phase of stabilization (plateau phase), GO tends to improve and eventually inactivates (inactive or burnt-out phase). Minimal-to-mild GO often remits spontaneously, but complete restitutio ad integrum almost never occurs when GO is more than mild. Several risk factors contribute to its development on a yet undefined genetic background. Cigarette smoking is the most important of them. Early diagnosis, control and removal of modifiable risk factors, early treatment of mild forms of GO may effectively limit the risk of progression to more severe forms, which have a profound and dramatic impact on the quality of life of affected individuals, and remain a therapeutic challenge, often requiring long-lasting and multiple medical and surgical therapies.

Thyrotropin Receptor Blocking Antibodies

Autoantibodies (Ab) against the thyroid-stimulating hormone receptor (TSHR) are frequently found in autoimmune thyroid disease (AITD). Autoantibodies to the TSHR (anti-TSHR-Ab) may mimic or block the action of TSH or be functionally neutral. Measurement of anti-TSHR-Ab can be done either via competitive-binding immunoassays or with functional cell-based bioassays. Antibody-binding assays do not assess anti-TSHR-Ab functionality, but rather measure the concentration of total anti-TSHR binding activity. In contrast, functional cell-based bioassays indicate whether anti-TSHR-Ab have stimulatory or blocking activity. Historically bioassays for anti-TSHR-Ab were research tools and were used to study the pathophysiology of Graves' disease and Hashimoto's thyroiditis. In the past, bioassays for anti-TSHR-Abs were laborious and time-consuming and varied widely in performance from laboratory to laboratory. Recent advances in the development of cell-based assays, including the application of molecular engineering, have led to significant improvements that have enabled bioassays to be employed routinely in clinical laboratories. The prevalence and functional significance of TSHR blocking autoantibodies (TBAb) in autoimmune hypothyroidism has been less well investigated compared to TSHR stimulating Ab. There is an increasing body of data, however, that demonstrate the clinical utility and relevance of TBAb, and thus the importance of TBAb bioassays, in the diagnosis and management of patients with AITD. In the present review, we summarize the different methods used to measure TBAb, and discuss their prevalence and clinical relevance.

Stimulatory TSH-Receptor Antibodies and Oxidative Stress in Graves Disease

CONTEXT

We hypothesized that TSH-receptor (TSHR) stimulating antibodies (TSAbs) are involved in oxidative stress mechanisms in patients with Graves disease (GD).

METHODS

Nicotinamide adenine dinucleotide phosphate oxidase, isoform 2 (NOX2); oxidative parameters; and oxidative burst were measured in serum, urine, and whole blood from patients with GD and control subjects. Superoxide production was investigated in human embryonic kidney (HEK)-293 cells stably overexpressing the TSHR. Lipid peroxidation was determined by immunodot-blot analysis for protein-bound 4-hydroxy-2-nonenal (4-HNE) in human primary thyrocytes and HEK-293-TSHR cells.

RESULTS

Serum NOX2 levels were markedly higher in hyperthyroid untreated vs euthyroid treated patients with GD, hyperthyroid patients with toxic nodular goiter, and euthyroid healthy control subjects (all P < 0.0001). Urine oxidative parameters were increased in patients with GD vs patients with toxic goiter (P < 0.01) and/or control subjects (P < 0.001). The maximum of the zymosan A- and phorbol 12,13-dibutyrate-induced respiratory burst of leukocytes was 1.5-fold higher in whole blood from hyperthyroid patients with GD compared with control subjects (P < 0.001 and P < 0.05). Monoclonal M22 TSAbs stimulated cAMP (HEK cells) in a dose-dependent manner. M22 (P = 0.0082), bovine TSH (P = 0.0028), and sera of hyperthyroid patients with GD (P < 0.05) increased superoxide-specific 2-hydroxyethidium levels in HEK-293 TSHR cells after 48-hour incubation vs control subjects. In contrast, triiodothyronine (T3) did not affect reactive oxygen species (ROS) production. In primary thyrocytes, the 4-HNE marker was higher in patients with GD vs control subjects at 6 and 48 hours (P = 0.02 and P = 0.04, respectively). Further, after 48-hour incubation of HEK-293 TSHR cells with patient sera, 4-HNE was higher in patients with untreated GD compared with control subjects (P < 0.05).

CONCLUSIONS

Monoclonal M22 and polyclonal serum TSAbs augment ROS generation and/or induce lipid peroxidation.

2018 European Thyroid Association Guideline for the Management of Graves' Hyperthyroidism

Graves' disease (GD) is a systemic autoimmune disorder characterized by the infiltration of thyroid antigen-specific T cells into thyroid-stimulating hormone receptor (TSH-R)-expressing tissues. Stimulatory autoantibodies (Ab) in GD activate the TSH-R leading to thyroid hyperplasia and unregulated thyroid hormone production and secretion. Diagnosis of GD is straightforward in a patient with biochemically confirmed thyrotoxicosis, positive TSH-R-Ab, a hypervascular and hypoechoic thyroid gland (ultrasound), and associated orbitopathy. In GD, measurement of TSH-R-Ab is recommended for an accurate diagnosis/differential diagnosis, prior to stopping antithyroid drug (ATD) treatment and during pregnancy. Graves' hyperthyroidism is treated by decreasing thyroid hormone synthesis with the use of ATD, or by reducing the amount of thyroid tissue with radioactive iodine (RAI) treatment or total thyroidectomy. Patients with newly diagnosed Graves' hyperthyroidism are usually medically treated for 12-18 months with methimazole (MMI) as the preferred drug. In children with GD, a 24- to 36-month course of MMI is recommended. Patients with persistently high TSH-R-Ab at 12-18 months can continue MMI treatment, repeating the TSH-R-Ab measurement after an additional 12 months, or opt for therapy with RAI or thyroidectomy. Women treated with MMI should be switched to propylthiouracil when planning pregnancy and during the first trimester of pregnancy. If a patient relapses after completing a course of ATD, definitive treatment is recommended; however, continued long-term low-dose MMI can be considered. Thyroidectomy should be performed by an experienced high-volume thyroid surgeon. RAI is contraindicated in Graves' patients with active/severe orbitopathy, and steroid prophylaxis is warranted in Graves' patients with mild/active orbitopathy receiving RAI.

Performance and Specificity of 6 Immunoassays for TSH Receptor Antibodies: A Multicenter Study

BACKGROUND

The measurement of TSH receptor (TSHR) antibodies is warranted for diagnosis of Graves' disease (GD).

OBJECTIVE

The performance, detection sensitivity, and specificity of 6 TSHR immunoassays were compared.

METHODS

Two bioassays and 4 binding assays (Kronus, Immulite, Kryptor, Dynex) were compared in a dilution study performed in patients with autoimmune thyroid disease. Both bioassays were compared to 2 binding assays using stimulatory (M22) and blocking (K1-70) monoclonal antibody (MAb) mixtures.

RESULTS

Thirty samples from stimulatory (TSAb)-positive/blocking (TBAb)-negative patients with GD were diluted serially and measured in all assays. Samples were positive until dilution 1:2,187 in the TSAb bioassay, 1:81 in the Immulite (p < 0.002 vs. bioassay) and Kronus ELISA (p = 0.039) assays, and 1:27 in the Kryptor and Dynex ELISA (p < 0.001 vs. bioassay). Ten samples from TBAb-positive/TSAb-negative patients with GD or Hashimoto's thyroiditis were positive in all binding assays. None of the binding assays differentiated between TSAb and TBAb. Mixtures of 100% K1-70 (200 ng/mL), 80% K1-70 + 20% M22, 60% K1-70 + 40% M22, 40% K1-70 + 60% M22, 20% K1-70 + 80% M22, and 100% M22 (20 ng/mL) tested positive in both Immulite (26.4, 20.2, 15.2, 10.5, 6.3, 2.00 IU/L) and Kronus assays (27.1, 23.3, 19.3, 12.0, 5.7, 2.2 IU/L). These MAb mixtures were tested in the TBAb bioassay and showed 82, 61, 24 (negative), -26 (negative), -77 (negative), and -95% (negative) inhibition, respectively.

CONCLUSIONS

The sample dilution study showed higher detection sensitivity for the TSAb bioassay, and the antibody mixture study demonstrated exclusive specificity of the bioassays over all automated and ELISA binding assays.

Prevalence and clinical relevance of thyroid stimulating hormone receptor-blocking antibodies in autoimmune thyroid disease

The prevalence and clinical relevance of thyroid stimulating hormone (TSH) receptor (TSHR) blocking antibodies (TBAb) in patients with autoimmune thyroid disease (AITD) was investigated. Serum TBAb were measured with a reporter gene bioassay using Chinese hamster ovary cells. Blocking activity was defined as percentage inhibition of luciferase expression relative to induction with bovine TSH alone (cut-off 40% inhibition). All samples were measured for TSHR stimulatory antibody (TSAb) and TSHR binding inhibiting immunoglobulins (TBII). A total of 1079 unselected, consecutive patients with AITD and 302 healthy controls were included. All unselected controls were negative for TBAb and TSAb. In contrast, the prevalence of TBAb-positive patients with Hashimoto's thyroiditis and Graves' disease was 67 of 722 (9·3%) and 15 of 357 (4·2%). Of the 82 TBAb-positive patients, thirty-nine (48%), 33 (40%) and 10 (12%) were hypothyroid, euthyroid and hyperthyroid, respectively. Ten patients were both TBAb- and TSAb-positive (four hypothyroid, two euthyroid and four hyperthyroid). Thyroid-associated orbitopathy was present in four of 82 (4·9%) TBAb-positive patients, with dual TSHR antibody positivity being observed in three. TBAb correlated positively with TBII (r = 0·67, P < 0·001) and negatively with TSAb (r = -0·86, P < 0·05). The percentage of TBII-positive patients was higher the higher the level of inhibition in the TBAb assay. Of the TBAb-positive samples with  > 70% inhibition, 87% were TBII-positive. Functional TSHR antibodies impact thyroid status. TBAb determination is helpful in the evaluation and management of patients with AITD. The TBAb assay is a relevant and important tool to identify potentially reversible hypothyroidism.

Graves' orbitopathy as a rare disease in Europe: a European Group on Graves' Orbitopathy (EUGOGO) position statement

Background

Graves’ orbitopathy (GO) is an autoimmune condition, which is associated with poor clinical outcomes including impaired quality of life and socio-economic status. Current evidence suggests that the incidence of GO in Europe may be declining, however data on the prevalence of this disease are sparse. Several clinical variants of GO exist, including euthyroid GO, recently listed as a rare disease in Europe (ORPHA466682).

The objective was to estimate the prevalence of GO and its clinical variants in Europe, based on available literature, and to consider whether they may potentially qualify as rare. Recent published data on the incidence of GO and Graves’ hyperthyroidism in Europe were used to estimate the prevalence of GO. The position statement was developed by a series of reviews of drafts and electronic discussions by members of the European Group on Graves’ Orbitopathy. The prevalence of GO in Europe is about 10/10,000 persons. The prevalence of other clinical variants is also low: hypothyroid GO 0.02–1.10/10,000; GO associated with dermopathy 0.15/10,000; GO associated with acropachy 0.03/10,000; asymmetrical GO 1.00–5.00/10,000; unilateral GO 0.50–1.50/10,000.

Conclusion

GO has a prevalence that is clearly above the threshold for rarity in Europe. However, each of its clinical variants have a low prevalence and could potentially qualify for being considered as a rare condition, providing that future research establishes that they have a distinct pathophysiology. EUGOGO considers this area of academic activity a priority.

Thyroid-Stimulating Hormone Receptor Antibodies in Pregnancy: Clinical Relevance

Graves' disease is the most common cause of thyrotoxicosis in women of childbearing age. Approximately 1% of pregnant women been treated before, or are being treated during pregnancy for Graves' hyperthyroidism. In pregnancy, as in not pregnant state, thyroid-stimulating hormone (TSH) receptor (TSHR) antibodies (TRAbs) are the pathogenetic hallmark of Graves' disease. TRAbs are heterogeneous for molecular and functional properties and are subdivided into activating (TSAbs), blocking (TBAbs), or neutral (N-TRAbs) depending on their effect on TSHR. The typical clinical features of Graves' disease (goiter, hyperthyroidism, ophthalmopathy, dermopathy) occur when TSAbs predominate. Graves' disease shows some peculiarities in pregnancy. The TRAbs disturb the maternal as well as the fetal thyroid function given their ability to cross the placental barrier. The pregnancy-related immunosuppression reduces the levels of TRAbs in most cases although they persist in women with active disease as well as in women who received definitive therapy (radioiodine or surgery) before pregnancy. Changes of functional properties from stimulating to blocking the TSHR could occur during gestation. Drug therapy is the treatment of choice for hyperthyroidism during gestation. Antithyroid drugs also cross the placenta and therefore decrease both the maternal and the fetal thyroid hormone production. The management of Graves' disease in pregnancy should be aimed at maintaining euthyroidism in the mother as well as in the fetus. Maternal and fetal thyroid dysfunction (hyperthyroidism as well as hypothyroidism) are in fact associated with several morbidities. Monitoring of the maternal thyroid function, TRAbs measurement, and fetal surveillance are the mainstay for the management of Graves' disease in pregnancy. This review summarizes the biochemical, immunological, and therapeutic aspects of Graves' disease in pregnancy focusing on the role of the TRAbs in maternal and fetal function.

Highly variable sensitivity of five binding and two bio-assays for TSH-receptor antibodies

PURPOSE

TSH-receptor (TSHR) antibodies (Ab) can be measured with binding or bio-assays. Sensitivity and specificity of five binding and two bio-assays were compared.

METHODS

TSHR-blocking (TBAb) and TSHR-stimulating (TSAb) Ab were measured with reporter bio-assays. Blocking activity was defined as percent inhibition of luciferase expression relative to induction with bTSH alone. TSAb was reported as percentage of specimen-to-reference ratio (SRR%). TSHR-binding inhibitory immunoglobulins (TBII) were measured with Kronus, Dynex, Kryptor, Cobas, and Immulite.

RESULTS

Sixty patients with Graves' disease (GD), 20 with Hashimoto's thyroiditis (HT), and 20 healthy controls (C) were included. C tested negative in all assays (specificity 100 %) while all 60 hyperthyroid GD patients tested positive in the TSAb bio-assay (sensitivity 100 %). Among these 60 GD patients, 20 had low TSAb positivity (SRR% 140-279), but were TBII positive in only 20 (100 %), 7 (35 %), 9 (45 %), 11 (55 %), and 18 (90 %) using the Kronus, Dynex, Kryptor, Cobas, and Immulite, respectively. In 20 moderate TSAb-positive (SRR% 280-420) patients, TBII tested positive in 20 (100 %), 14 (70 %), 13 (65 %), 16 (80 %), and 19 (95 %), respectively. The high (SRR% > 420) TSAb-positive patients were all TBII positive. All 20 hypothyroid HT patients tested TBAb positive (sensitivity 100 %) in the bio-assay while they tested TBII positive in 20 (100 %), 18 (90 %), 20, 20, and 18, respectively. Results obtained with two luminometers correlated for TSAb positive (r = 0.99, p < 0.001), TBAb positive (r = 0.88, p < 0.001), and C (r = 0.86, p < 0.001). None of the binding assays differentiated between TSAb and TBAb.

CONCLUSIONS

Sensitivity is highly variable between binding and bio-assays for TSHR-Abs.

Analytical Performance and Validation of a Bioassay for Thyroid-Blocking Antibodies

BACKGROUND AND OBJECTIVE

A cell-based bioassay for the measurement of thyroid blocking autoantibodies (TBAb) has been recently reported. The analytical performance and validation of this bioassay is assessed and described.

METHODS

Chinese hamster ovary cells expressing a chimeric thyrotropin receptor were treated with bovine (b) TSH and different concentrations of an immunoglobulin G (IgG) monoclonal human TBAb (K1-70). TBAb was measured as a function of luciferase activity relative to bTSH alone and expressed as percent inhibition. Results obtained in the chimeric cell line were compared with those of a wild-type cell line. Analytical performance studies were subsequently performed with the chimeric cell line only.

RESULTS

Immunodepletion of K1-70 IgG by using a protein G-Sepharose column showed that positive percent inhibition in the TBAb bioassay was detectable from K1-70 IgG only. The limit of blank was determined to be 12.2%. The limit of detection was 14% inhibition, equivalent to 0.4 ng/mL K1-70, while the limit of quantitation was 22% (coefficient of variation [CV] 12%) equivalent to 0.625 ng/mL K1-70. The dynamic range was between 14 ± 3.7 (mean % inhibition ± standard deviation) and 101 ± 2.6, equivalent to 0.4-10 ng/mL K1-70. The linear range was between 22 ± 2.6 and 93 ± 0.6 inhibition, equivalent to 0.625-5 ng/mL K1-70. The upper limit of the 99th percent reference range was 34% inhibition. In two laboratories, CV values for the intra- and inter-assay precisions for K1-70 ranged from 2% to 12% and from 1.7% to 14.5%, respectively. For patient sera, the CV values for the intra- and inter-assay precisions ranged from 3% to 9% and from 3% to 11%, respectively. No interference was found when follicle-stimulating hormone, luteinizing hormone, and human chorionic gonadotrophin were tested in the TBAb bioassay. The median of % inhibition values in 40 TBAb positive sera from patients with autoimmune thyroid disease were 93.5 (range 25-103) and 92 (range 64-107) for the wild type and chimeric cell lines, respectively. Further, all 40 samples of patients with various non-thyroidal autoimmune diseases were TBAb negative.

CONCLUSIONS

This TBAb bioassay exhibits excellent analytical performance and high level of reproducibility.

Prevalence, Phenotype, and Psychosocial Well-Being in Euthyroid/Hypothyroid Thyroid-Associated Orbitopathy

BACKGROUND

At the onset of thyroid-associated orbitopathy (TAO), most patients are hyperthyroid, while scarce data are available on euthyroid/hypothyroid TAO. The aim of this study was to assess the prevalence, phenotype, and psychosocial burden of patients with initially euthyroid/hypothyroid TAO.

METHODS

The medical records of 461 consecutive and unselected patients with TAO followed at a specialized joint thyroid-eye clinic were analyzed within this retrospective cross-sectional study. Main outcome measures were the prevalence of initially eu- or hypothyroid TAO as well as ophthalmic signs and symptoms, disease-specific quality of life (QoL), work impairment, and rate of psychotherapy in initially eu-/hypothyroid versus hyperthyroid TAO.

RESULTS

The prevalences of eu-/hypothyroid and hyperthyroid TAO were 4.3% (n=20; [confidence interval, CI, 2.6-6.3]) and 95.7% (n=441; [9.37-9.74]), respectively. In 12 patients (2.6% [CI 1.3-4.3]), Hashimoto's thyroiditis was present and in 8 (1.7% [CI 0.7-3.0]) no thyroid disease was noted at the time of inclusion. One (0.05%) patient with eu-/hypothyroid TAO and 172 (39%) with hyperthyroid TAO had clinically active TAO (p=0.001). In eu-/hypothyroid versus hyperthyroid patients, 14 (70%) versus 135 (30.6%) had a mild TAO, 6 (30%) versus 183 (64.2%) a moderate-to-severe TAO, and 0 versus 23 (5.4%) had a sight-threatening TAO (p<0.001). TAO was asymmetric in 4 (20%) eu-/hypothyroid and in 27 (6.1%) hyperthyroid patients (p=0.038). Only 5.3% versus 30.2% and 10.5% versus 44.1% of patients with eu-/hypothyroid and hyperthyroid TAO, respectively, were on sick leave (p=0.003) or work disabled (p=0.018). QoL was less impaired in eu-/hypothyroid versus hyperthyroid TAO (median visual functioning and appearance scores: 100 versus 75; p<0.001 and 81.25 versus 75; p=0.315). Of patients with eu-/hypothyroid and hyperthyroid TAO, 15% and 20.2% had psychotherapy respectively (p=0.409). Eu-/hypothyroid TAO was positively (odds ratio 7.05, p=0.060) and negatively (odds ratio: 0.09, p=0.026) associated with a unilateral involvement and thyrotropin-receptor autoantibodies respectively.

CONCLUSIONS

Compared with hyperthyroid TAO, QoL and working ability are less impaired in eu-/hypothyroid TAO with an often asymmetric and less severe clinical phenotype.

Standardization of a bioassay for thyrotropin receptor stimulating autoantibodies

BACKGROUND

Cell-based bioassays for functional thyroid stimulating autoantibodies (TSAb) are sensitive diagnostic tools. However, there is no bioassay available that is standardized with international reference material. We aimed to promote the standardization of the test results among laboratories that perform TSAb bioassays and calibrate TSAb levels against the second international standard (IS) 08/204 from the National Institute for Biological Standards and Control (NIBSC).

METHODS

Serum TSAb activity was measured with a FDA-cleared bioassay that utilizes CHO cells expressing a chimeric thyrotropin receptor (TSHR) and a c-AMP response-element-dependent luciferase. The IS was applied for calibration. TSAb results were reported as percentage of specimen-to-reference ratio (SRR%) and converted into mIU/L.

RESULTS

The IS dose-response curve was obtained using concentrations from 0.3125 to 200 mIU/L. Mean TSAb SRR%±standard deviation (SD) values for the IS concentrations 0.3125, 0.625, 1.25, 2.5, 5, 10, 20, 40, 60, 80, 100, 120, 160, and 200 mIU/L were 63±4 (CV 6.3%), 63±4 (6.3), 67±2 (3.0), 76±6 (7.9), 91±8 (8), 134±8 (5.9), 201±13 (6.5), 294±12 (4.1), 336±10 (3.0), 348±8 (2.3), 360±14 (3.8), 371±15 (4.0), 381±9 (2.4), and 389±10 (2.6), respectively. A total of 127 dilution experiments were performed using 12 high TSAb-positive sera from patients with Graves' disease. When diluting TSAb-positive sera, IS concentrations within the linear range 5, 10, 20, 40, and 80 mIU/L were used for the calibration curve. All standard curves had R(2) values >0.95. Low coefficient of variation (CV %) values for the IS calibration curve (4-6%) were obtained. Compared to bovine TSH, no significant differences were noted using either a pool of healthy donors or a normal serum as reference controls. The average IU measured value for the assay cutoff (SRR 140%) corresponded to 9.54±1.68 mIU/L, and clinical application was shown in 60 Graves' patients.

CONCLUSIONS

The TSAb bioassay demonstrated excellent performance in terms of linear range, limit of quantitation, and imprecision. The dilution experiments showed a high correlation coefficient and excellent reproducibility. Thus, TSAb levels can be reliably converted from SRR% to IU/L. These results offer the perspective of standardizing TSAb levels among laboratories and enable more accurate comparison of TSAb studies.

Thyroid Stimulating but Not Blocking Autoantibodies Are Highly Prevalent in Severe and Active Thyroid-Associated Orbitopathy: A Prospective Study

The clinical utility of the functional TSH receptor autoantibodies was prospectively evaluated in patients with thyroid-associated orbitopathy (TAO). Ophthalmic, endocrine, and serological investigations were performed in 101 consecutive patients with severe and active TAO. Serum thyroid stimulating (TSAb) and blocking (TBAb) antibody levels were measured with two bioassays using cells that express a chimeric TSH receptor and CRE-dependent luciferase. TSAb results are expressed as percentage of specimen-to-reference ratio (SRR %). Blocking activity is defined as percent inhibition of luciferase expression relative to induction with bovine TSH alone. All 101 consecutively followed-up patients with severe and active TAO were TBAb negative. In contrast, 91 (90%) were TSAb positive of whom 90 had Graves' disease. Serum TSAb levels correlated with the diplopia score (P = 0.016), total severity eye score (P = 0.009), proptosis (P = 0.007), lid aperture (P = 0.003), upper lid retraction (P = 0.006), keratopathy (P = 0.04), and thyroid binding inhibiting immunoglobulins (TBII, P < 0.001) and negatively with the duration of TAO (P = 0.002). Median serum values of TSAb were SRR% 418 (range 28% to 795%). TSAb, not TBAb, are highly prevalent in severe/active TAO and serum TSAb levels correlate with clinical disease severity.

Thyroid-associated orbitopathy is linked to gastrointestinal autoimmunity

Common autoimmune disorders tend to co-exist in the same subjects and cluster in families. The objective of this study was to determine the prevalence of autoimmune co-morbidity in patients with autoimmune thyroid disease (AITD) with and without thyroid-associated orbitopathy (TAO). This was a cross-sectional study conducted at an academic tertiary referral centre. Of 1310 patients with AITD [n = 777 or 59% with Graves' disease (GD) and n = 533, 41% with Hashimoto's thyroiditis (HT)] followed at a specialized joint thyroid-eye out-patient clinic, 176 (13·4%) had an adult type of the autoimmune polyglandular syndrome, 129 (9·8%) type 1 diabetes, 111 (8·5%) coeliac disease, 60 (4·6%) type A autoimmune gastritis, 57 (4·4%) vitiligo and 25 (1·9%) Addison's disease. Coeliac disease and autoimmune gastritis were associated positively with GD [odds ratio (OR) = 2·18; P = 0·002 and OR = 6·52; P < 0·001], whereas type 1 diabetes, Addison's disease, autoimmune primary hypogonadism, alopecia areata, rheumatoid arthritis and Sjögren's syndrome were 'protective' for GD and thus linked to HT, OR = 0·49 (P < 0·001), 0·06 (P < 0·001), 0·25 (P < 0·001), 0·50 (P = 0·090) and 0·32 (P = 0·003), respectively. Of 610 (46·6%) AITD patients with TAO, 584 (95·7%) and 26 (4·3%) had GD and HT, respectively (P < 0·001). TAO was most prevalent in GD patients with coeliac disease (94%, OR = 1·87, P < 0·001). Multivariate analysis showed high OR for coeliac disease and autoimmune gastritis (3·4 and 4·03, both P < 0·001) pertaining to the association with TAO while type 1 diabetes, Addison's disease and alopecia areata were protective for TAO. In patients with TAO, coeliac disease is the most prevalent co-morbid autoimmune condition and rates are increased compared to GD patients without TAO.

Autoimmune thyroid disorders

Autoimmune thyroid diseases (AITD) result from a dysregulation of the immune system leading to an immune attack on the thyroid. AITD are T cell-mediated organ-specific autoimmune disorders. The prevalence of AITD is estimated to be 5%; however, the prevalence of antithyroid antibodies may be even higher. The AITD comprise two main clinical presentations: Graves' disease (GD) and Hashimoto's thyroiditis (HT), both characterized by lymphocytic infiltration of the thyroid parenchyma. The clinical hallmarks of GD and HT are thyrotoxicosis and hypothyroidism, respectively. The mechanisms that trigger the autoimmune attack to the thyroid are still under investigation. Epidemiological data suggest an interaction among genetic susceptibility and environmental triggers as the key factor leading to the breakdown of tolerance and the development of disease. Recent studies have shown the importance of cytokines and chemokines in the pathogenesis of AT and GD. In thyroid tissue, recruited T helper 1 (Th1) lymphocytes may be responsible for enhanced IFN-γ and TNF-α production, which in turn stimulates CXCL10 (the prototype of the IFN-γ-inducible Th1 chemokines) secretion from the thyroid cells, therefore creating an amplification feedback loop, initiating and perpetuating the autoimmune process. Associations exist between AITD and other organ specific (polyglandular autoimmune syndromes), or systemic autoimmune disorders (Sjögren's syndrome, rheumatoid arthritis, systemic lupus erythematosus, systemic sclerosis, cryoglobulinemia, sarcoidosis, psoriatic arthritis). Moreover, several studies have shown an association of AITD and papillary thyroid cancer. These data suggest that AITD patients should be accurately monitored for thyroid dysfunctions, the appearance of thyroid nodules, and other autoimmune disorders.

Clinical relevance of thyroid-stimulating autoantibodies in pediatric graves' disease-a multicenter study

CONTEXT AND OBJECTIVE

The incidence of TSH receptor (TSHR) stimulating autoantibodies (TSAbs) in pediatric Graves' disease (GD) is controversial. This large, multicenter study evaluated the clinical relevance of TSAbs in children with GD both with Graves' orbitopathy (GO) and without orbital disease.

DESIGN

We conducted a cross-sectional retrospective study.

SETTING

Sera were collected in seven American and European academic referral centers and evaluated in a central laboratory. PATIENTS AND SAMPLES: A total of 422 serum samples from 157 children with GD, 101 control individuals with other thyroid and nonthyroid autoimmune diseases, and 50 healthy children were studied.

MAIN OUTCOME MEASURES

TSAbs were measured using a novel, chimeric TSHR bioassay and a cAMP response element-dependent luciferase. TSH binding-inhibitory Ig (TBII) and parameters of thyroid function were also determined.

RESULTS

In 82 untreated children with GD, sensitivity, specificity, and positive and negative predictive values for TSAb and TBII were: 100 and 92.68% (P = .031), 100 and 100%, 100 and 100%, and 100 and 96.15%, respectively. TSAb and TBII were present in 147 (94%) and 138 (87.9%) of the 157 children with GD (P < .039), respectively; and in 247 (94%) and 233 (89%) of the 263 samples from this group (P < .0075), respectively. In children with GD and GO, TSAb and TBII were noted in 100 and 96% (P < .001), respectively. Hyperthyroid children with GD and GO showed markedly higher TSAb levels compared to those with thyroidal GD only (P < .0001). No significant differences were noted for TBII between the two groups. After a 3-year (median) medical treatment, the decrease of TSAb levels was 69% in GD vs 20% in GD and GO (P < .001). All 31 samples of euthyroid children with GO were TSAb positive; in contrast, only 24 were TBII positive (P = .016). All children with Hashimoto's thyroiditis, nonautoimmune hyperthyroidism, type 1 diabetes, and juvenile arthritis and the healthy controls were TSAb and TBII negative.

CONCLUSIONS

Serum TSAb level is a sensitive, specific, and reproducible biomarker for pediatric GD and correlates well with disease severity and extrathyroidal manifestations.

Conformational inactivation induces immunogenicity of the receptor-binding pocket of a bacterial adhesin

Inhibiting antibodies targeting receptor-binding pockets in proteins is a major focus in the development of vaccines and in antibody-based therapeutic strategies. Here, by using a common mannose-specific fimbrial adhesin of Escherichia coli, FimH, we demonstrate that locking the adhesin in a low-binding conformation induces the production of binding pocket-specific, adhesion-inhibiting antibodies. A di-sulfide bridge was introduced into the conformationally dynamic FimH lectin domain, away from the mannose-binding pocket but rendering it defective with regard to mannose binding. Unlike the native, functionally active lectin domain, the functionally defective domain was potent in inducing inhibitory monoclonal antibodies that blocked FimH-mediated bacterial adhesion to epithelial cells and urinary bladder infection in mice. Inhibition of adhesion involved direct competition between the antibodies and mannose for the binding pocket. Binding pocket-specific inhibitory antibodies also were abundant in polyclonal immune serum raised against the functionally defective lectin domain. The monoclonal antibodies elicited against the binding-defective protein bound to the high-affinity conformation of the adhesin more avidly than to the low-affinity form. However, both soluble mannose and blood plasma more strongly inhibited antibody recognition of the high-affinity FimH conformation than the low-affinity form. We propose that in the functionally active conformation the binding-pocket epitopes are shielded from targeted antibody development by ligand masking and that strong immunogenicity of the binding pocket is unblocked when the adhesive domain is in the nonbinding conformation.