Blocking-type anti-TSH receptor antibodies and relation to responsiveness to antithyroid drug therapy and remission in Graves' disease

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.

TSAb/TRAb ratio as a sensitive screening test for active Graves' orbitopathy

OBJECTIVE

Graves' orbitopathy (GO), an extrathyroidal manifestation of Graves' disease, can seriously threaten the patient's quality of life. Given that immunosuppressive treatment during the early active phase of GO has been found to reduce both disease activity and severity, sensitive screening tests are needed.

METHODS

The present study included 86 patients with GO, in whom serum levels of thyroid-stimulating hormone (TSH), free T3, free T4, thyroid-stimulating antibody, TSH receptor antibody, thyroid peroxidase antibody, thyroglobulin, and thyroglobulin antibody were measured within 2 months before magnetic resonance imaging (MRI)for orbit assessment.

RESULTS

The thyroid-stimulating antibody/TSH receptor antibody ratio was able to distinguish MRI results with a correct classification rate of 81%. When focusing on patients without T3 predominant Graves' diseases, the ratio distinguished MRI results at a rate of 92%. Receiver operating characteristic curve analysis revealed a cutoff antibody ratio of 87, which yielded a sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of 91%, 95%, 18.2, and 0.0957, respectively, for distinguished MRI results.

CONCLUSIONS

The thyroid-stimulating antibody/TSH receptor antibody ratio is a highly sensitive and specific indicator for active GO, especially in patients without T3 predominance, and serves as a good screening test for active GO in primary care settings.

General properties of autoimmune thyroid diseases and associated morbidities

Background Autoimmune thyroid diseases (ATDs) can be classified into two basic diseases: Graves' disease (GD) and Hashimoto's thyroiditis (HT). Here, we review the effectiveness of laboratory and imaging methods used for the early diagnosis of ATD and draw attention to methods that may improve screening. Methods Retrospective data of 142 patients diagnosed with ATD between January 2010 and December 2015 at our paediatric endocrinology clinic were used. Sociodemographic characteristics, clinical findings, treatments and follow-up data of patients were statistically evaluated. Results Of the ATD cases, 81% (n = 115) were female. The median age was 12.5 ± 3.5 (range 1-17) years and 91% (n = 129) of patients were in puberty. There was a significant positive correlation between the height (standard deviation score) and follow-up time for patients with HT (r = 0.156, p < 0.01). Thyroglobulin antibody (TgAb) positivity was found in 75% (45/60) of females with a positive maternal ATD history (p = 0.045). Thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), free thyroxine (fT4) values were significantly altered during the treatment follow-up period in female patients with GD and HT, while only fT4 values were found to be significantly altered in boys with HT. Conclusion Although GD and HT have similar mechanisms, they differ in terms of treatment duration and remission and relapse frequencies. Ultrasonography (USG) screening is a non-invasive procedure that is suitable for all patients with ATD. Based on our results, TgAb could be useful in the screening of girls with a history of maternal ATD.

A case of Graves' disease developing with exacerbation of sarcoidosis

A 53-year old female was referred to our hospital with bilateral abnormal shadow in the chest X-ray. Computed tomography revealed multifocal ill-defined densities and thickening of bronchial wall and pulmonary vessels by fine nodules combined with massive enlargement of bilateral mediastinal and hilar lymph nodes. Analyses of bronchoalveolar lavage fluid and transbronchial lung biopsy specimen showed the increase in CD4/CD8 ratio and the presence of non-caseating granulomas, respectively. In addition, serum angiotensin-converting enzyme was extremely high, leading to the diagnosis of sarcoidosis. Simultaneously, she complained of palpitation and sweating. Endocrinological examination showed comorbid hyperthyroidism without anti-TSH receptor antibody (TRAb). In the first 2-3 months, pulmonary shadow gradually disappeared without steroid administration. In parallel, serum thyroid hormone levels were gradually normalized in the beginning, but increased after 3 months with an appearance of TRAb. After initiation of treatment with antithyroid agent, hyperthyroidism was improved within 9 months, and changed into hypothyroidism thereafter. The clinical course of this rare case suggest that immunological storm by exacerbation of sarcoidosis may trigger the onset of autoimmune thyroid disease, in which hyperthyroidism with stimulating type of TRAb subsequently changed into hypothyroidism with blocking-type TRAb.

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.

The Presence of Thyroid-Stimulation Blocking Antibody Prevents High Bone Turnover in Untreated Premenopausal Patients with Graves' Disease

Osteoporosis-related fractures are one of the complications of Graves’ disease. This study hypothesized that the different actions of thyroid-stimulating hormone receptor (TSHR) antibodies, both stimulating and blocking activities in Graves’ disease patients might oppositely impact bone turnover. Newly diagnosed premenopausal Graves’ disease patients were enrolled (n = 93) and divided into two groups: patients with TSHR antibodies with thyroid-stimulating activity (stimulating activity group, n = 83) and patients with TSHR antibodies with thyroid-stimulating activity combined with blocking activity (blocking activity group, n = 10). From the stimulating activity group, patients who had matched values for free T4 and TSH binding inhibitor immunoglobulin (TBII) to the blocking activity group were further classified as stimulating activity-matched control (n = 11). Bone turnover markers BS-ALP, Osteocalcin, and C-telopeptide were significantly lower in the blocking activity group than in the stimulating activity or stimulating activity-matched control groups. The TBII level showed positive correlations with BS-ALP and osteocalcin levels in the stimulating activity group, while it had a negative correlation with the osteocalcin level in the blocking activity group. In conclusion, the activation of TSHR antibody-activated TSH signaling contributes to high bone turnover, independent of the actions of thyroid hormone, and thyroid-stimulation blocking antibody has protective effects against bone metabolism in Graves’ disease.

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.

Bioassays for TSH-receptor autoantibodies: an update

Immunoglobulins in patients with Graves' disease (GD) that modulate the thyroid stimulating hormone receptor (TSH-R) do so via stimulating cAMP dependent signals (TSI), blocking TSH or inhibition of TSH-receptor activation (TBI) or inducing apoptotic signals. These functional immunoglobulins represent powerful biomarkers of anti-self reactivity in the thyroid and systemic tissues that harbor TSH-R expressing target cells. TSI on thyrocytes induce hyperthyroidism, and TSI on TSH-R fibroblasts of orbital muscles, skin and heart provoke the release of cytokines and antigen-specific T-cell responses leading to systemic inflammation. Bioassays of anti-TSH-R autoantibodies provide decisive information on GD activity. This review examines the past and present bioassays in GD. The critical goal of cell-based anti-TSH-R autoantibody bioassays, to identify the pathogenic immunoglobulins in GD under robust and standardized conditions suitable for routine clinical laboratory practice, is discussed.

[Antireceptor and antichannel autoantibodies]

This review of literature concerns the different autoantibodies directed against membrane receptors and ion channels. The target antigens, the associated pathologies, the pathogenesis and the methods of detection of these autoantibodies will be addressed. Some of these autoantibodies are thought to be closely related to the autoimmune disease whereas for some others their pathogenesis role is still unclear. Overall, the roles of antibodies are different between diseases, but the presence of such autoantibodies support the basis of intervening immunotherapy, antibody titers predicted the activity of the diseases and some of them are very specific and become the useful markers for the diagnosis. Some autoantibodies are detected routinely as the antiacetylcholine receptor, voltage-gated potassium and calcium channels autoantibodies whereas most of them are detected very rarely and only by specialized laboratories. This review will be divided in three parts with the following classification: the first group of autoantibodies directed against membrane receptors included receptors with an enzymatic activity (mostly tyrosine kinase) with one transmembrane domain, receptors associated to G protein with seven transmembrane domains, ion channels and receptors associated to the membrane by the glycosyl phosphatidyl inositol and the second group of intracellular receptor autoantibodies directed to the estrogens, androgens, lamin and kinesin receptors.

A bioluminescence assay for thyrotropin receptor antibodies predicts serum thyroid hormone levels in patients with de novo Graves' disease

BACKGROUND

TSH receptor antibodies (TBII) in Graves' disease (GD) may be TSH receptor stimulating (TSAb) and blocking (TBAb) antibodies. In commercially available assays however, only total TBII titres can be measured, without discriminating between TSAb and TBAb.

OBJECTIVE

To design a TBII bioassay to detect of TSAb and to correlate TSAb activity with severity of hyperthyroidism in de novo GD patients.

PATIENTS

Thirty-five patients with de novo GD and 27 controls.

METHODS

The JP-26-26 cell line, which constitutively expresses the TSH receptor (TSHR), was stably transfected with a cyclic adenosine monophosphate responsive element--luciferase construct. The clone B1 exhibited a near linear increase in luminescence from 0.2 mU/l to 50 mU/l bovine TSH and was used as a TBII bioassay. TBII, free T4 and TSH were measured in the sera of all patients and controls.

RESULTS

In the sera of 35 GD patients, TBII titres did not correlate with serum free T4 concentrations. In contrast, a strong and highly significant correlation was found between TSHR stimulating activity (luminescence) as measured with the TBII bioassay and serum free T4 levels (R = 0.80, P < 0.001). Interestingly, the luminescence/TBII ratio had a wide range at low TBII titres, whereas high TBII titres were associated with a low degree of TSHR activation. The TBII bioassay also detected TBAb in GD patients who spontaneously developed hypothyroidism.

CONCLUSIONS

The B1-TBII-bioassay as developed in our laboratory has a high sensitivity for the detection of TSAb in GD and predicts the severity of hyperthyroidism in untreated GD patients. In addition, we found that high TBII titres are associated with weak TSHR activation.

Longitudinal correlation of thyroid-stimulating immunoglobulin with clinical activity of disease in thyroid-associated orbitopathy

PURPOSE

To investigate the possible correlation between the changes in inflammatory active phase of thyroid-associated orbitopathy (TAO) with measured changes in thyroid-stimulating immunoglobulin (TSI) levels over time. This study was undertaken to evaluate the potential usefulness of measured TSI values in following and treating patients with TAO.

METHODS

A retrospective chart analysis was performed on 23 patients who had been referred to a tertiary care oculoplastics service between July of 2002 and April of 2004 with suspected TAO. The activity status of patients with TAO was graded by using the TAO activity scale (TAOS), created to distinguish between the active and cicatricial phases of TAO. Laboratory values of TSI reported during the course of the study period were compiled for each study patient.

RESULTS

Linear regression analysis revealed a statistical correlation between the changes in activity of TAO, as measured by the TAOS score, and changes in measured values of TSI over time. A statistically significant correlation was also found between the activity of TAO (measured by the TAOS score) and TSI value.

CONCLUSIONS

It was found that changes in inflammatory phase of TAO, as measured by the TAOS score, statistically correlate with changes in measured TSI. An additional correlation was also found between the absolute score of TAO activity and measured level of TSI. These findings suggest that serial TSI measurements may be an adjunct in assessing clinical inflammatory activity of TAO and may help direct clinical decision making regarding treatment decisions in TAO.