Novel chimeric thyroid-stimulating hormone-receptor bioassay for thyroid-stimulating immunoglobulins

US-based, Prospective, Blinded Study of Thyrotropin Receptor Antibody in Autoimmune Thyroid Disease

CONTEXT

Bioassays provide information on the functionality of thyrotropin receptor antibodies (TSH-R-Ab) and thus may offer more clinical utility than binding assays.

OBJECTIVE

In this prospective, blinded, US-based study, the clinical performance of several TSH-R-Ab assays was compared.

SETTING

US endocrinology clinic.

SUBJECTS

One hundred sixty-two unselected, consecutive, well-documented patients with various thyroid diseases and healthy controls.

INTERVENTION(S)

Blinded TSH-R-Ab measurements.

MAIN OUTCOME MEASURE(S)

Sensitivity and specificity of 4 TSH-R-Ab assays.

RESULTS

The 4 TSH-R-Ab assays were negative in all 42 patients without autoimmune thyroid disease (AITD). In 104 patients with Graves' disease (GD), irrespective of the disease duration, TSH-R-Ab positivity was present in 65 (63%), 67 (65%), and 87 (84%) for the Cobas and Immulite binding assays and stimulatory TSH-R-Ab [thyroid-stimulating immunoglobin (TSI)] bioassay, respectively (TSI vs Immulite P < .0025, TSI vs Cobas P < .0009). Fifteen newly diagnosed GD patients were all positive in the TSI bioassay, but only 11 (73%) were positive in the Cobas and Immulite binding assays. Nine GD patients with biochemical subclinical hyperthyroidism were TSI-positive but Immulite- and Cobas-negative. Two GD patients were blocking TSH-R-Ab [thyroid-blocking immunoglobin (TBI)]-positive and TSI-negative, and the Immulite and Cobas were positive in both. Additional serum samples from AITD patients that consisted of 30 TBI-positive and 10 TSI-positive samples were blindly tested in the binding assays. Only 6 of the 10 TSI-positive samples were positive in both binding assays, and 30 and 28 of the TBI-positive samples were positive in the Cobas and Immulite assays, respectively.

CONCLUSION

Binding TSH-R-Ab assays are less sensitive than TSI bioassays and are not specific for stimulating antibodies. Measuring the function of TSH-R-Ab in a bioassay can provide useful information to clinicians.

Thyroid stimulating receptor autoantibodies

Thyroid-stimulating hormone receptor autoantibodies (TRAbs) play a crucial role as pathogenic antibodies in both the diagnosis and management of Graves' disease (GD). GD, an autoimmune disease resulting from a combination of genetic and environmental factors, is the most common cause of hyperthyroidism. With advancements in technology for TRAb detection and the availability of automated commercial kits, TRAb has become an essential clinical laboratory marker for the diagnosis of GD, as well as extra-thyroidal manifestations like Graves' ophthalmopathy (GO). This article provides a comprehensive review of TRAb, encompassing its clinical assays along with its significance in the clinical setting.

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.

The phenotype of Graves' orbitopathy is associated with thyrotropin receptor antibody levels

PURPOSE

Graves' orbitopathy (GO) is a specific inflammatory disorder of the orbit characterized by a highly heterogeneous clinical phenotype. The role of thyrotropin receptor antibodies (TSH-R-Ab) has been widely researched, however there is still no evidence that these antibodies have a direct pathogenic role in this pathology. The aim of this study was to examine their relation to the individual clinical features of GO.

METHODS

Ninety-one consecutive patients with GO were recruited. Total antibody concentration (TSH-R binding inhibitory immunoglobulins, TBII) and their functional activity (stimulating TSH-R-Ab, TSAb) were measured using binding immunoassay and cell-based bioassay, respectively.

RESULTS

Both TSAb and TBII levels were significantly associated to the clinical parameters of GO activity. TSAb was a more sensitive serological marker compared to TBII pertaining to eyelid retraction and edema, proptosis, extra-orbital muscle disorders, diplopia, irritable eye symptoms, and photophobia. TSAb, but not TBII, was a significant predictive marker of conjunctival redness, chemosis, caruncle/plica inflammation, eye irritation, and orbital pain, (odds ratio: 3.096, p = 0.016; 5.833, p = 0.009; 6.443, p = 0.020; 3.167, p = 0.045; 2.893, p = 0.032; versus 2.187, p = 0.093; 2.775, p = 0.081; 3.824, p = 0.055; 0.952, p = 0.930; 2.226, p = 0.099, respectively). Neither TSAb nor TBII correlated with the level of proptosis (ρ = 0.259, p = 0.090, and ρ = 0.254, p = 0.104, respectively), however rising TSAb levels were strongly associated to the level of proptosis.

CONCLUSIONS

TSH-R-Ab were significantly associated with GO's phenotype. Especially TSAb, as a sensitive and predictive serological biomarker, can improve diagnosis and management of GO.

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.

Clinical relevance of thyroid-stimulating immunoglobulin as a biomarker of the activity of thyroid eye disease

BACKGROUND/OBJECTIVES

Although it has been reported that thyroid-stimulating immunoglobulin (TSI) is associated with the clinical characteristics of thyroid eye disease (TED), there is a paucity of literature regarding the role of TSI in diagnosing active TED. This study investigated the relationship between the level of TSI and the activity of TED and assessed the cut-off value of TSI discriminating active TED from inactive TED.

METHODS

This cross-sectional study included 101 patients with TED. TSI was quantitatively measured with a cell-based bioassay using a chimeric TSH receptor and a cyclic adenosine monophosphate response element-dependent luciferase. The association between TSI and a variety of demographic and clinical features of TED was analysed. Multivariate regression analysis was performed to determine possible independent factors affecting the level of TSI.

RESULTS

TSI level was higher in males than in females (p = 0.023) and smokers than in nonsmokers (p = 0.004). TSI level was inversely correlated with the duration of ocular symptoms (r = -0.295, p = 0.003). The level of TSI was also significantly different when compared to the thyroid function (p = 0.003), TED activity (p < 0.001), and TED severity (p = 0.001). Multivariate regression analysis revealed a significant relationship between TED activity and thyroid function jointly and the TSI level. The cut-off level of TSI for predicting active TED was a specimen-to-reference ratio of 406.7 (p < 0.001, area under the curve = 0.847, sensitivity 77.4%, specificity 81.3%).

CONCLUSIONS

TSI was a functional biomarker strongly associated with TED activity even after being adjusted by other clinical characteristics. Serum TSI level may help identify patients with active TED in clinics.

Longitudinal association of thyroid-stimulating immunoglobulin levels with clinical characteristics in thyroid eye disease

OBJECTIVES

The clinical course of thyroid eye disease (TED) is heterogeneous and predicting patients who may develop the severe sequelae of the disease is difficult. In this study, we evaluated the longitudinal association between changes in serum thyroid-stimulating hormone (TSH) receptor antibody (TRAb) levels and course of disease activity and severity over time.

DESIGN

This was a multicentre, prospective, observational study.

SETTING

Fifteen tertiary care oculoplastic service centres in Korea.

PARTICIPANTS

Seventy-six patients with newly diagnosed TED were included and followed up for 12 months.

METHODS

We evaluated clinical characteristics and serum TRAb levels at baseline, 6 and 12 months of TED diagnosis. Additionally, we analysed longitudinal associations between the serum TRAb levels and clinical activity score (CAS), no signs or symptoms, only signs, soft tissue involvement, proptosis, extraocular muscle involvement, corneal involvement, sight loss (NOSPECS) score and proptosis.

RESULTS

Thyroid-stimulating immunoglobulin (TSI) and TSH-binding inhibitory immunoglobulin (TBII) levels decreased during the 1-year follow-up, whereas disease activity measured using CAS decreased mainly in the first 6 months. Disease severity measured using NOSPECS score and proptosis remained unchanged. Moreover, inter-person differences in TBII levels were associated with CAS, NOSPECS score and proptosis over time, whereas inter-person differences in TSI levels were associated with NOSPECS score. Subgroup analysis of patients with a baseline CAS≥4 demonstrated that within-person changes in TSI levels affected the CAS and NOSPECS score.

CONCLUSIONS

Follow-up measurement of serum TSI and TBII levels may help evaluate TED prognosis and enable accurate clinical decision-making.

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.

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).

Predicting the Course of Graves' Orbitopathy Using Serially Measured TSH-Receptor Autoantibodies by Automated Binding Immunoassays and the Functional Bioassay

The aim of the study was to investigate the use of serial measurements of TSH-receptor autoantibodies (TRAb) with the newest available assay technology to predict the course of Graves' Orbitopathy (GO) during the first 24 months from disease onset. Serial serum samples from patients with GO (103 mild/135 severe) were collected between 2007 and 2017 and retrospectively analyzed. The course of GO were classified into mild/severe 12 months after manifestation (severe: NOSPECS≥5; mild<5). TRAb were measured with automated binding immunoassays (IU/l): TRAb Elecsys (Cobas, Roche), TRAb bridge assay (IMMULITE, Siemens), and a cell-based bioassay (percent of specimen to reference ratio - SRR%) (Thyretain, Quidel). Variable cut off levels of measured TRAb were calculated at specificity of 90% from receiver operator curve (ROC) analysis for several timepoints during the course of GO. To select one: 5-8 months after first GO symptoms, which is the timepoint for usual referals for treatment mild course could be predicted at cut offs of 1.5 IU/l (Elecsys), 0.8 IU/l (Immulite) and 402% SRR (Thyretain) and the risc of severe course has to be anticipated if TRAb are above 11.6 IU/l (Elecsys), 6.5 IU/l (Thyretain), and 714% SRR (Thyretain). The Thyretain bioassay showed the highest diagnostic sensitivity (using the commercial cut off's) over the entire follow up period. TRAb measurements during the 24-month follow up of GO provide added value to the GO clinical activity and severity scores and should be used especially in the event of an unclear decision-taking situation with regard to therapy.

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.

Predicting the Relapse of Hyperthyroidism in Treated Graves' Disease with Orbitopathy by Serial Measurements of TSH-Receptor Autoantibodies

The aim of this study was to investigate the potential of the new TSH-receptor antibody (TRAb) assays to predict remission or relapse of hyperthyroidism in patients with Graves' disease (GD) and Graves' orbitopathy (GO). TRAbs were measured retrospectively in sera from a cohort of GD patients with GO (n=117; remission n=38 and relapse n=79-Essen GO biobank) with automated binding immunoassays: TRAb Elecsys (Cobas Roche) and TRAb bridge assay (IMMULITE, Siemens), and the TSAb (thyroid stimulating Ab) cell-based bioassay (Thyretain, Quidel Corp.). To identify relapse risk/remission of hyperthyroidism patients were followed up at least 10 months after the end of antithyroid drug therapy (ATD) therapy. ROC plot analysis was performed to calculate cut-off levels of TRAb and TSAb for prediction of relapse and remission of hyperthyroidism. Cut-off serum levels are provided for timepoints around 3, 6, 10, and 15 months after the beginning of ATD. Repeated measurements of TRAb increase the rate of relapses predictions to 60% (Elecsys), 70% (IMMULITE), and 55% (Thyretain). Patients with remission have consistently TRAb levels below the cut off for relapse in repeated measurements. The cell-based bioassay was the most sensitive - and continued to be positive during follow up [at 15 months: 90% vs. 70% (IMMULITE) and 65% (Elecsys)]. Identification of relapsing hyperthyroidism is possible with automated immunoassays and cell-based bioassay especially with serial TRAb measurements during the course of ATD therapy. Patient who need eye surgery may profit from an early decision towards definitive treatment.

Quality of life of patients with thyroid eye disease: 3-year follow-up in a multidisciplinary clinic in Israel

BACKGROUND

Changes in the quality of life (QOL) of patients with thyroid eye disease (TED) were examined during a 3-year follow-up in a multidisciplinary eye clinic, and factors that may improve QOL were identified.

METHODS

A retrospective review of medical records of all patients who attended the TED clinic at Sheba Medical Center, Israel, from May 2016 to May 2019 was performed. The retrieved data included demographics, comprehensive ophthalmic examination findings, clinical activity scores (CAS), laboratory test results, and QOL assessments by the Graves' Orbitopathy QOL (GO-QOL) questionnaire.

RESULTS

One hundred thirty-two TED clinic patients were examined. Thirty patients (22.72%) received medical treatment consisting of steroids according to the European Group on Graves' Orbitopathy (EUGOGO) protocol, high-dose steroids, or immunosuppressive drugs. Twenty-eight patients (21.21%) underwent surgical rehabilitation (decompression, strabismus, or eyelid surgery). There was a significant increase in total QOL score after steroid treatment according to the EUGOGO protocol, after decompression surgery, and after strabismus surgery compared to pre-treatment total QOL (p=0.04, p=0.021, and p=0.042, respectively, matched pairs). In addition, there were significant positive correlations between the changes in the total QOL score and the change in thyroid-stimulating immunoglobulin (TSI) as well as the change in CAS among the patients who underwent medical and surgical interventions.

CONCLUSIONS

QOL improved significantly after medical/surgical treatments. A change in the CAS and in the TSI may also correlate with change in QOL. Periodic evaluation of TED patients' QOL is recommended for enhanced and more comprehensive management.

The prognostic value of thyroid-stimulating immunoglobulin in the management of Graves' disease

BACKGROUND

The bioassay of thyroid-stimulating immunoglobulin was reported to have a similar performance to the commonly used thyroid-stimulating hormone binding inhibition assay, also known as thyroid receptor antibody assay. The normal reference range of thyroid receptor antibody levels indicates the withdrawal of anti-thyroid drugs in the recent clinical guidelines.

METHODS

A prospective, longitudinal observational study was conducted to evaluate the prognostic value of thyroid-stimulating immunoglobulin in patients with Graves' disease.

RESULTS

A total of 77 patients with Graves' disease treated with anti-thyroid drugs were in a continuous follow-up until 1 year after anti-thyroid drugs discontinuation. Commercial kits of thyroid-stimulating immunoglobulin and M22-thyroid-stimulating hormone binding inhibition assay were used and compared. Thyroid-stimulating immunoglobulin was all negative in healthy controls, Hashimoto thyroiditis, and subacute thyroiditis. Thyroid-stimulating immunoglobulin value was highest in untreated patients with Graves' disease (p < 0.001). Under anti-thyroid drugs treatment, thyroid-stimulating immunoglobulin value decreased gradually. A total of 21 patients had positive thyroid-stimulating immunoglobulin at the end of treatment. According to clinical fate of patients with Graves' disease after withdrawal of anti-thyroid drugs, thyroid-stimulating immunoglobulin value and positivity in patients with relapse were significantly higher than that reported in patients with remission (p = 0.001, p < 0.001). After adjustment for age, gender, initial thyroid receptor antibody, initial thyroid-stimulating immunoglobulin, and thyroid receptor antibody at the end of treatment, the odds ratio of positive thyroid-stimulating immunoglobulin for the risk of relapse was 33.271 (95% confidence interval: 4.741-233.458, p < 0.001) and odds ratio of quantitative thyroid-stimulating immunoglobulin was 1.009 (95% confidence interval: 1.002-1.015, p < 0.001).

CONCLUSION

Thyroid-stimulating immunoglobulin is a good predictor of relapse in patients with Graves' disease treated with anti-thyroid drugs. It might be safer to discontinue anti-thyroid drugs when thyroid-stimulating immunoglobulin and thyroid receptor antibody were both negative.

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.

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.

High Titers of Thyrotropin Receptor Antibodies Are Associated With Orbitopathy in Patients With Graves Disease

CONTEXT

Serum TSH receptor autoantibody (TSH-R-Ab) is a biomarker of Graves disease (GD). Studies have shown that the levels of this TSH-R-Ab have clinical significance.

OBJECTIVE

To differentiate between thyroidal GD only and Graves orbitopathy (GD + GO).

DESIGN

Controlled, follow-up study.

SETTING

Academic tertiary referral center for GD + GO.

SUBJECTS

Sixty patients with GD, GD + GO, and controls.

INTERVENTION

Serial serum dilution analyses with six automated, ELISA, and cell-based assays for TSH-R-Ab.

MAIN OUTCOME MEASURE

Differentiation among GD phenotypes.

RESULTS

All undiluted samples of hyperthyroid-untreated GD patients were positive with the six assays but became negative at dilution 1:9 in four of six assays. In contrast, all undiluted samples of hyperthyroid-untreated GD + GO patients remained positive up to dilution 1:81, P < 0.001. At high dilutions 1:243, 1:729, 1:2187, and 1:6561, the rate of stimulating TSH-R-Ab positivity in the bioassay for GD + GO patients was 75%, 35%, 5%, and 0%, respectively (all P < 0.001). The five ELISA and/or automated assays confirmed this marked difference of anti-TSH-R-Ab detection between GD-only and GD + GO. In comparison, the baseline-undiluted samples of GD vs GD + GO showed an overlap in the ranges of TSH-R-Ab levels. Subsequent to 12-month methimazole treatment, samples from euthyroid GD + GO patients were still TSH-R-Ab positive at the high dilution of 1:243. In contrast, all GD samples were negative already at dilution 1:3. A GD patient with TSH-R-Ab positivity at dilution 1:729 developed de novo GO.

CONCLUSIONS

TSH-R-Ab titers, as determined by dilution analysis, significantly differentiate between GD and GD + GO.

Comparison of Five TSH-Receptor Antibody Assays in Graves' disease: results from an observational pilot study

BACKGROUND

Early diagnosis and relapse prediction in Graves' disease influences treatment. We assessed the abilities of four TSH-receptor antibody tests [TRAb] and one cyclic adenosine monophosphate bioassay to predict relapse of Graves' disease.

METHODS

Observational study investigating patients presenting with Graves' disease at a Swiss hospital endocrine referral center or an endocrine outpatient clinic. Main outcomes were diagnosis and relapse of Graves' disease after stop of anti-thyroid drugs. We used Cox regression to study associations of TRAb levels with relapse risk and calculated c-statistics [AUC] to assess discrimination. Blood draws took place as close as possible to treatment initiation.

RESULTS

AUCs ranged from 0.90 (TSAb Biossay by RSR) to 0.97 (IMMULITE TSI by Siemens). Highest sensitivity (94.0%) was observed for IMMULITE TSI and RSR TRAb Fast, while the greatest specificity (97.9%) was found with the EliA anti-TSH-R (by Thermo Fisher). In Cox regression analysis comparing the highest versus the lower quartiles, the highest hazard ratio [HR] for relapse was found for BRAHMS TRAK (by Thermo Fisher) (2.98, 95% CI 1.13-7.84), IMMULITE TSI (2.40, 95% CI 0.91-6.35), EliA anti-TSH-R (2.05, 95% CI 0.82-5.10), RSR Fast TRAb (1.80, 95% CI 0.73-4.43), followed by RSR STIMULATION (1.18, 95% CI 0.46-2.99). Discrimination analyses showed respective AUCs of 0.68, 0.65, 0.64, 0.64, and 0.59.

CONCLUSION

The assays tested had good diagnostic power and relapse risk prediction with few differences among the new assays. Due to the small sample size and retrospective design with possible selection bias, our data need prospective validation.

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.

Thyroid Stimulating Hormone Receptor Antibodies in Thyroid Eye Disease-Methodology and Clinical Applications

BACKGROUND

Thyroid stimulating hormone receptor antibodies (TSHR-Ab) cause autoimmune hyperthyroidism and are prevalent in patients with related thyroid eye disease (TED).

PURPOSE

To provide a historical perspective on TSHR-Ab and to present evidence-based recommendations for clinical contemporary use.

METHODS

The authors review the recent literature pertaining to TSHR-Ab in patients with TED and describe the various immunoassays currently used for detecting TSHR-Ab and their clinical applications.

RESULTS

We provide a historical summary and description of the various methods used to detect TSHR-Ab, foremost, the functional TSHR-Ab. Increasing experimental and clinical data demonstrate the clinical usefulness of cell-based bioassays for measurements of functional TSHR-Ab in the diagnosis and management of patients with autoimmune TED and in the characterization of patients with autoimmune-induced hyperthyroidism and hypothyroidism. Thyroid stimulating hormone receptor antibodies, especially the functional stimulating antibodies, are sensitive, specific, and reproducible biomarkers for patients with autoimmune TED and correlate well with clinical disease activity and clinical severity. Unlike competitive-binding assays, bioassays have the advantage of indicating not only the presence of antibodies but also their functional activity and potency.

CONCLUSIONS

Measurement of TSHR-Ab (especially stimulating antibodies) is a clinically useful tool for the management of patients with TED.

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.

Evaluation of the first fully automated immunoassay method for the measurement of stimulating TSH receptor autoantibodies in Graves' disease

BACKGROUND

Thyroid stimulating hormone (TSH) receptor autoantibodies (TRAb) are pathogenetic and diagnostic hallmarks of Graves' disease (GD). Three varieties of TRAb have been described: stimulating (S-TRAb), blocking (B-TRAb), and apoptotic (A-TRAb) autoantibodies. Very recently, the first immunoassay method (Immulite TSI assay, Siemens Healthcare Diagnostics) declared to measure serum S-TRAb concentration, has been made available in an automated commercial platform. The aim of the study was to evaluate the ability of this new test to identify patients suffering from GD, in comparison with two current IMA methods for total TSH receptor autoantibodies (T-TRAb) measurement.

METHODS

Sera of 383 subjects [72 patients with untreated GD, 55 patients with autoimmune thyroiditis (AIT), 36 patients with multinodular non-toxic goiter, 100 patients with other non-thyroid autoimmune diseases (NTAD) and 120 healthy subjects (HS)] were evaluated.

RESULTS

The threshold obtained by receiver operating characteristic (ROC) analysis was 0.54 IU/L, very similar to that proposed by the manufacturer (0.55 IU/L). Thyroid-stimulating immunoglobulins (TSI) were positive in all GD patients and negative in all but three controls (clinical sensitivity and specificity of 100% and 98.7%, respectively). Passing and Bablok regression analysis and Bland-Altman plot showed an acceptable agreement between TSI Immulite assay and other two immunoassay methods (Cobas/Elecsys, Roche and TRAK RIA, BRAHMS Thermo Scientific).

CONCLUSIONS

The diagnostic performance of fully automated Immulite TSI assay in GD patients is at least comparable to that of current TRAb immunoassays (IMAs) suggesting the possibility of including such assay in rapid and cost-saving diagnostic and monitoring algorithms. However, our results do not provide full evidence that this assay is specific for S-TRAb only, and future studies comparing Immulite TSI assay to stimulating activity are required.

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.

Thyroid dysfunction in the era of precision medicine

The launching of the Precision Medicine Initiative by the President of the United States in January 2015 was an invitation for all healthcare professionals to review their practice. This call should stimulate thyroidologists working in different areas (from basic research or epidemiology to the frontline of the clinical arena or to those designing public health programs) to be aware of this new outlook. The aim of the initiative is to eradicate imprecision in estimating the probability of a correct diagnosis, to be as sure as possible of the most effective treatment, and to maximize the chances of a successful outcome. This paper summarizes some of the current challenges faced by endocrinologists in the field of thyroid dysfunction, and illustrates how precision medicine may improve diagnosis and therapy in the future.

Usefulness of Measuring Thyroid Stimulating Antibody at the Time of Antithyroid Drug Withdrawal for Predicting Relapse of Graves Disease

BACKGROUND

Hyperthyroidism relapse in Graves disease after antithyroid drug (ATD) withdrawal is common; however, measuring the thyrotropin receptor antibody (TRAb) at ATD withdrawal in order to predict outcomes is controversial. This study compared measurement of thyroid stimulatory antibody (TSAb) and thyrotropin-binding inhibitory immunoglobulin (TBII) at ATD withdrawal to predict relapse.

METHODS

This retrospective study enrolled patients with Graves disease who were treated with ATDs and whose serum thyroid-stimulating hormone levels were normal after receiving low-dose ATDs. ATD therapy was stopped irrespective of TRAb positivity after an additional 6 months of receiving the minimum dose of ATD therapy. Patients were followed using thyroid function tests and TSAb (TSAb group; n=35) or TBII (TBII group; n=39) every 3 to 6 months for 2 years after ATD withdrawal.

RESULTS

Twenty-eight patients (38%) relapsed for a median follow-up of 21 months, and there were no differences in baseline clinical characteristics between groups. In the TSAb group, relapse was more common in patients with positive TSAb at ATD withdrawal (67%) than patients with negative TSAb (17%; P=0.007). Relapse-free survival was shorter in TSAb-positive patients. In the TBII group, there were no differences in the relapse rate and relapse-free survivals according to TBII positivity. For predicting Graves disease relapse, the sensitivity and specificity of TSAb were 63% and 83%, respectively, whereas those of TBII were 28% and 65%.

CONCLUSION

TSAb at ATD withdrawal can predict the relapse of Graves hyperthyroidism, but TBII cannot. Measuring TSAb at ATD withdrawal can assist with clinical decisions making for patients with Graves disease.

Decreased proportions of CD4 + IL17+/CD4 + CD25 + CD127- and CD4 + IL17+/CD4 + CD25 + CD127 - FoxP3+ T cells in children with autoimmune thyroid diseases (.)

Until now, altered balance of Th1 and Th2 immune cells has been postulated to play an important role in the pathogenesis of autoimmune thyroid diseases (AITD). However, recent studies on thyroid diseases have suggested a new role for Th17 cells that have been classified as a new lineage, distinct from Th1, Th2 and Treg cells. Despite wide interest, the role of Th17 cells in the pathogenesis of inflammatory and autoimmune diseases is still debated. The aim of the study was to estimate the proportions of Th17/Treg T cells in peripheral blood from patients with Graves' disease (GD; n = 29, mean age 15.4 ± 5.1 years), Hashimoto's thyroiditis (HT; n = 39, mean age 15.2 ± 4.1 years) and in healthy controls (n = 49, mean age 14.8 ± 3 years). Polychromatic flow cytometry and several fluorochrome-conjugated monoclonal antibodies were applied to delineate Th17 and Treg cells. The analysis of Th17/Treg T cell proportions in peripheral blood from patients with Graves' disease revealed significantly lower ratios of CD4 + IL17+/CD4 + CD25 + CD127 - (p < 0.0021) and CD4 + IL17+/CD4 + CD25 + CD127 - FoxP3 + (p < 0.0031) than in the control group. In addition, in the case of HT, we observed a significant decrease in the ratios of CD4 + IL17+/CD4 + CD25 + CD127 - (p < 0.0001) and CD4 + IL17+/CD4 + CD25 + CD127 - FoxP3 + (p < 0.0001) T cells in comparison to healthy children. In patients with untreated GD, a statistically significant positive correlation was found between the proportions of CD4 + IL17+/CD4 + CD25 + CD127-, CD4 + IL17+/CD4 + CD25 + CD127 - FoxP3+ T cells and the TRAbs (R = 0.71, p < 0.029; R = 0.72, p < 0.026, respectively) and a positive correlation was noted between the percentage of CD4 + CD - IL - 17 + T cells and the level of TSAbs (R = 0.66, p < 0.037). We conclude that the changes in the proportion of Th17/Treg T cells in peripheral blood and their significant relationship with the level of anti-thyroid antibodies indicate an involvement of these cells in the pathogenesis of AITD.

A 2013 European survey of clinical practice patterns in the management of Graves' disease

OBJECTIVE

Management of Graves' disease (GD) in Europe was published in 1987. Aim of this survey was to provide an update on clinical practice in Europe, and to compare it with a 2011 American survey.

DESIGN

Members of the European Thyroid Association (ETA) were asked to participate in a survey on management of GD, using the same questionnaire of a recent American survey.

RESULTS

A total of 147 ETA members participated. In addition to serum TSH and free T4 assays, most respondents would request TSH-receptor autoantibody (TRAb) measurement (85·6%) and thyroid ultrasound (70·6%) to confirm aetiology, while isotopic studies were selected by 37·7%. Antithyroid drug (ATD) therapy was the preferred first-line treatment (83·8%). Compared to the previous European survey, Europeans currently more frequently use TRAb measurement and thyroid ultrasound for diagnosis and evaluation, but first-line treatment remains ATDs in a similar percentage of respondents. Current clinical practice patterns differ from those in North America, where isotopic studies are more frequently used, and radioiodine (RAI) still is first-line treatment. When RAI treatment is selected in the presence of mild Graves' orbitopathy and/or associated risk factors for its occurrence/exacerbation, steroid prophylaxis is frequently used. The preferred ATD in pregnancy is propylthiouracil in the first trimester and methimazole in the second and third trimesters, similar to North America.

CONCLUSIONS

Significant changes in clinical practice patterns in Europe were noted compared to the previous European survey, as well as persisting differences in diagnosis and therapy between Europe and North America.

Outcome Prediction of Treatment of Graves' Hyperthyroidism with Antithyroid Drugs

Graves' disease is the most common cause of hyperthyroidism in iodine-replete areas and is ultimately due to antibodies interacting with the TSH receptor on thyroid follicular cells [TSH-receptor antibody (TRAb)]. Antithyroid drugs (ATDs) belonging to the family of thionamides are the first-line treatment in Europe. ATD treatment is commonly continued for 18-24 months. Its major limitation is the high rate of relapses after drug withdrawal. Factors particularly bound to subsequent relapses are the large thyroid volume, smoking habit, persistence of TRAb in the circulation at the end of treatment, and the post-partum period. Under these conditions, consideration should be given to a definitive therapy for hyperthyroidism (radioiodine treatment, thyroidectomy), particularly if the patient is at risk of cardiovascular complications that might be exacerbated by persistence or recurrence of hyperthyroidism.

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-stimulating immunoglobulins as measured in a reporter bioassay are not detected in patients with Hashimoto's thyroiditis and ophthalmopathy or isolated upper eyelid retraction

Although ophthalmopathy is mainly associated with Graves' hyperthyroidism, milder eye changes are also found in about 25% of patients with Hashimoto's thyroiditis (HT). The recent finding of negative thyrotropin receptor (TSHR) antibodies, as measured in the Thyretain™ thyroid-stimulating immunoglobulin (TSI) reporter bioassay, in patients with euthyroid Graves' disease raises the possibility that TSHR antibodies are not the cause of ophthalmopathy in all situations. Here, we have tested serum from patients with HT with and without ophthalmopathy or isolated upper eyelid retraction (UER) for TSHR antibodies, using the TSI reporter bioassay and collagen XIII as a marker of autoimmunity against the orbital fibroblast. Study groups were 23 patients with HT with ophthalmopathy, isolated UER, or both eye features and 17 patients without eye signs. Thyretain™ TSI results were expressed as a percentage of the sample-to-reference ratio, with a positive test being taken as a sample-to-reference ratio of more than 140%. Serum collagen XIII antibodies were measured in standard enzyme-linked immunosorbent assay. TSI tests were positive in 22% of patients with HT with no eye signs but in no patient with eye signs. In contrast, TSI tests were positive in 94% of patients with Graves' ophthalmopathy. Tests were negative in all normal subjects tested. Collagen XIII antibodies were detected in 83% of patients with ophthalmopathy, UER, or both eye features, but in only 30% of patients with no eye signs. Our findings suggest that TSHR antibodies do not play a major role in the pathogenesis of ophthalmopathy or isolated UER in patients with HT. Moreover, the role of TSHR antibodies in the development of ophthalmopathy in patients with Graves' disease remains to be proven. In contrast, collagen XIII antibodies appear to be a good marker of eye disease in patients with HT.

Applications of cell-based bioassays measuring the induced expression of endogenous genes

Cell-based bioassays are used to determine the biological activity of complex biotherapeutic products, to assign potency and to assure the quality and consistency of the manufacturing process. Clinically, these assays are used to assess bioactivity in patient samples, particularly for the detection of antidrug neutralizing antibodies. Owing to their versatility, cellular assays that measure endogenous gene expression by quantitative reverse transcription PCR offer a rapid and automatable alternative to assays measuring functional, late-stage responses. Notably, detection of immediate early gene expression represents a direct response of the cell to receptor ligation by the biotherapeutic. We review current developments in the use of this approach and demonstrate its application to the detection of receptor-binding autoantibodies using, as a case study, the detection of autoantibodies to the thyroid-stimulating hormone receptor.

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.

Thyroid function. Pathogenesis of Graves ophthalmopathy--a role for TSH-R?

A new study highlights the complexities of anti-TSH-receptor antibody function and the differences between adult and paediatric patients with Graves disease, adding to the controversy regarding the possible role of these antibodies in the development of ophthalmopathy.

Association between TSH-Receptor Autoimmunity, Hyperthyroidism, Goitre, and Orbitopathy in 208 Patients Included in the Remission Induction and Sustenance in Graves' Disease Study

Background. Graves' disease may have a number of clinical manifestations with varying degrees of activity that may not always run in parallel. Objectives. To study associations between serum levels of TSH-receptor autoantibodies and the three main manifestations of Graves' disease (hyperthyroidism, goiter, and presence of orbitopathy) at the time of diagnosis of hyperthyroidism. Methods. We describe a cohort of 208 patients with newly diagnosed Graves' hyperthyroidism. Patients were enrolled in a multiphase study of antithyroid drug therapy of Graves' hyperthyroidism, entitled "Remission Induction and Sustenance in Graves' Disease (RISG)." Patients were systematically tested for degree of biochemical hyperthyroidism, enlarged thyroid volume by ultrasonography, and the presence of orbitopathy. Results. Positive correlations were found between the levels of TSH-receptor autoantibodies in serum and the three manifestations of Graves' disease: severeness of hyperthyroidism, presence of enlarged thyroid, and presence of orbitopathy, as well as between the different types of manifestations. Only around half of patients had enlarged thyroid gland at the time of diagnosis of hyperthyroidism, whereas 25-30% had orbitopathy. Conclusions. A positive but rather weak correlation was found between TSH-receptor antibodies in serum and the major clinical manifestation of Graves' disease. Only half of the patients had an enlarged thyroid gland at the time of diagnosis.

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

Autoantibodies to the thyrotrophin (TSH) receptor (anti-TSHR) are unique, in that they are involved directly in the pathophysiology of certain autoimmune thyroid diseases (AITD). Thyroid-stimulating antibodies (TSAb) act as agonists that activate the thyroid gland and cause Graves' disease. Other anti-TSHR antibodies block TSH and can cause hypothyroidism. Thyroid-blocking antibodies (TBAb) have not been studied as extensively as TSAb. We developed a TBAb bioassay based on a cell line that expresses a chimeric TSHR. The 50% inhibitory concentration of the chimeric Chinese hamster ovary (CHO)-Luc cells was more than five-fold lower compared with the wild-type CHO-Luc cells. We tested the performance of this bioassay using a thyroid-blocking monoclonal antibody K1-70, established an assay cut-off and detected TBAb in 15 of 50 (30%) patients with AITD. Interestingly, the assay detects both TSAb and TBAb and measures the net activity of a mixture of both types of antibodies. There was a high correlation (R(2) 0·9, P < 0·0001) between the results of the TSAb assay and the negative percentage inhibition of the TBAb assay. The TBAb bioassay was approximately 20-fold more sensitive than a commercially available TSHR binding assay (TRAb). In contrast to TRAb, sera with high levels of TBAb activity were able to be diluted several hundred-fold and still exhibit blocking activity above the cut-off level. Thus, this TBAb bioassay provides a useful tool for measuring the activity of anti-TSHR antibodies and may help clinicians to characterize the diverse clinical presentations of patients with AITD.

Correlation between TSH receptor antibody assays and clinical manifestations of Graves' orbitopathy

PURPOSE

To investigate an association between the levels of serum thyroid-stimulating hormone (TSH)-receptor autoantibodies (TRAbs) and Graves' orbitopathy (GO) activity/severity scores, and compare the performance of three different TRAb assays in assessing the clinical manifestations of GO.

MATERIALS AND METHODS

Cross-sectional study. Medical records of 155 patients diagnosed with GO between January 2008 and December 2010 were reviewed. GO activity was assessed by clinical activity score (CAS) and severity graded with the modified NOSPECS score by a single observer. Serum TRAb was measured by three different methods: 1st generation thyrotropin-binding inhibitor immunoglobulin (TBII) assay (TRAb1st); 3rd generation TBII assay (TRAb3rd); and biological quantitative assay of thyroid-stimulating immunoglobulin (TSI) using Mc4-CHO cells (Mc4-CHO TSI assay). Results were correlated with scores of activity/severity of thyroid eye disease.

RESULTS

All three assays (TRAb1st, TRAb3rd, and Mc4-CHO TSI) yielded results that were significantly positively correlated with CAS (β=0.21, 0.21, and 0.46, respectively; p<0.05) and proptosis (β=0.38, 0.34, and 0.33, respectively; p<0.05). Mc4-CHO TSI bioassay results were significantly positively correlated with all GO severity indices (soft tissue involvement, proptosis, extraocular muscle involvement, and total eye score; β=0.31, 0.33, 0.25, and 0.39, respectively; p<0.05).

CONCLUSION

Mc4-CHO TSI bioassay was superior over the two TBIIs in assessing active inflammation and muscle restriction due to GO, whereas TBII assay would be sufficient for evaluation of patients with proptosis.