Thyroid controversy--stimulating antibodies

Higher Risk of Incident Hyperthyroidism in Patients With Atrial Fibrillation

BACKGROUND

Atrial fibrillation (AF) has been linked to increased hyperthyroidism risk, but contributing factors are unclear.

OBJECTIVE

We aimed to investigate whether AF could predict hyperthyroidism and related risk factors.

METHODS

This retrospective cohort study was conducted in a tertiary medical institution and included patients aged 18 years or older with AF but without hyperthyroidism at diagnosis. The endpoint was defined as newly diagnosed hyperthyroidism during the follow-up period.

RESULTS

The study cohort included 8552 participants. Patients who developed new hyperthyroidism were younger and the proportion of females was higher. They had fewer comorbidities, including diabetes (26% vs 29%, P = .121), hypertension (51% vs 58%, P < .001), coronary artery disease (17% vs 25%, P < .001), stroke (16% vs 22%, P < .001), and end-stage renal disease (ESRD) (6% vs 10%, P = .001). The CHADS2 score was lower in patients with hyperthyroidism (1.74 vs 2.05, P = .031), but there was no statistically significant difference in the CHA2DS2-VASc and HAS-BLED score. Cox regression analysis identified younger age, female gender, history of congestive heart failure, hypertension, diabetes, non-ESRD status, and lower CHADS2 score but not CHA2DS2-VASc as independent predictors of incident hyperthyroidism during follow-up. We also propose a novel, simple risk stratification score (SAD HEC2 score) with excellent predictive power for incident hyperthyroidism during follow-up.

CONCLUSION

Our results provide insight into clinical risk factors for the development of hyperthyroidism in AF patients, as identified by the novel SAD HEC2 score. AF appears to be a common precursor of hyperthyroidism.

Evaluation of analytic and clinical performance of two immunoassays for detecting thyroid-stimulating receptor antibody in the diagnosis of Graves' disease

Objective

To evaluate the analytical and clinical performance of two immunoassays for diagnosis of Graves’ disease (GD), the Immulite thyroid‐stimulating immunoglobulin (TSI), and Elecsys Anti‐TSH receptor (TSHR) assay.

Methods

Precision and analytical measurement range were assessed using pooled samples of patients. The comparison between the two methods was evaluated using 579 clinical samples, and receiver operating characteristic (ROC) curves were drawn using the final diagnosis as reference. Clinical sensitivity and specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) were calculated for the two tests.

Results

The repeatability and intermediate imprecision coefficient of variation (CV%) of the TSI assay were 3.8% and 4.1% at 0.95 IU/L, and 3.5% and3.6% at 19.5 IU/L, respectively. The assays were linear over a range 0.27–38.5 IU/L. There was a high correlation between the quantitative results of the two methods (correlation coefficient r = 0.930). The cut‐off value obtained by ROC analysis for TSI assay was 0.7 IU/L with sensitivity of 93.7% and specificity of 85.1%. An overall qualitative agreement of 91.5% between two methods was observed. Among 44 patients with discordant qualitative results, the TSI assay provided more satisfactory results consistent with clinical diagnoses.

Conclusion

The TSI assay showed excellent analytical performance and provided a high PPV for GD.

Evaluation of the application of TSH receptor stimulating autoantibodies and the optimization of detection strategy in Graves' disease

BACKGROUND

We evaluated the use of thyroid stimulating immunoglobulin (TSI) assay to optimize the detection strategy for Graves' disease.

METHODS

Five hundred and forty-four well characterized serum samples from the Clinical Laboratory of Shanghai Tongren Hospital were collected from August 2019 to April 2020. The serum samples were obtained from 52 untreated GD patients, 155 treated GD patients, 83 patients with Hashimoto's thyroiditis, 70 patients with thyroid nodules, 83 patients with thyroid cancer, and 101 healthy subjects. All samples were evaluated by both TSI assay and TSH receptor autoantibodies (TRAb) assay. Moreover, 23 patients without a distinct thyroid disease diagnosis at the first visit were monitored for 6 months to make a final diagnosis.

RESULTS

The clinical sensitivity of the TSI and TRAb assays was 98.10% and 94.20% respectively, while the clinical specificity was 92.30% and 96.70% respectively. ROC plot analysis based on sera of UT-GD (newly diagnosed GD patients) revealed an area under the curve (AUC) of 0.974 for the TSI assay. The best cutoff value was 0.58 IU/l (98.0% of sensitivity, 92.8% of specificity). The AUC for the TRAb assay was 0.961. Furthermore, combining TSI and TRAb results, the area under the curve was 0.981. In a pilot study of 23 patients with an uncertain initial diagnosis, the follow-up results showed the clinical diagnosis of 22 out of 23 cases were resolved in agreement with the results obtained by the TSI assay, and one case matched the result obtained by TRAb assay.

CONCLUSION

The TSI assay presents very promising analytical characteristics and could be adopted in clinical practice to improve GD diagnosis. The TSI assay might be better than TRAb assay in initial differential diagnosis of GD from other thyroid diseases.

The Clinical Value and Variation of Antithyroid Antibodies during Pregnancy

Antithyroid antibodies, which include thyroid-stimulating hormone receptor antibodies (TRAbs), thyroid peroxidase antibodies (TPOAbs), and thyroid globulin antibodies (TgAbs), are widely known for their tight association with thyroid autoimmune diseases. The variation in all three kinds of antibodies also showed different trends during and after pregnancy (Weetman, 2010). This article reviewed the the physiological changes, while focusing on the variation of thyroid antibodies concentration in women during and after pregnancy, and adverse consequences related to their elevation. Since abnormal elevations of these antithyroid antibodies may lead to adverse outcomes in both mothers and fetuses, special attention must be paid to the titer of the antibodies during pregnancy. The molecular mechanisms of the variations in those antibodies have yet to be explained. The frequency and timing of thyroid antibody measurement, as well as different reference levels, also remain to be elucidated.

Clinical diagnosis of Graves' or non-Graves' hyperthyroidism compared to TSH receptor antibody test

BACKGROUND

TSH receptor antibody (TRAb) is considered the gold standard diagnostic test for the autoimmunity of Graves' disease (GD), which is commonly diagnosed clinically.

AIM

To evaluate the true positive (sensitivity) and true negative (specificity) rates of clinical diagnosis of GD or non-GD hyperthyroidism compared to the TRAb test.

SETTING

University teaching hospital in North West England.

PARTICIPANTS

Patients in the Endocrinology service who had a TRAb measurement between December 2009 and October 2015.

METHODS

Electronic patient records were studied retrospectively for a pre-TRAb clinical diagnosis of GD or non-GD hyperthyroidism. We examined descriptive statistics and binary classification tests; Fisher exact test was used to analyse contingency tables.

RESULTS

We identified 316 patients with a mean age of 45 (range, 17-89) years; 247 (78%) were women. Compared to the TRAb result, clinical diagnosis had a sensitivity of 88%, specificity 66%, positive predictive value 72%, negative predictive value 84%, false negative rate 12%, false positive rate 34%, positive likelihood ratio 2.6 and negative likelihood ratio 0.2 (P < 0.0001).

CONCLUSIONS

Clinicians were liable to both over- and under-diagnose GD. The TRAb test can help reduce the number of incorrect or unknown diagnoses in the initial clinical assessment of patients presenting with hyperthyroidism.

Long-Term Antithyroid Drug Treatment: A Systematic Review and Meta-Analysis

BACKGROUND

Several studies have reported inconsistent findings on the advantages and disadvantages of long-term treatment with antithyroid drugs (ATD). A systematic review and meta-analysis was undertaken to clarify the numerous aspects of long-term treatment with ATD.

METHODS

Medline and the Cochrane Library for trials published between 1950 and May 2016 were systematically searched. Studies containing data for long-term (>24 months) ATD treatment were included. Summary estimates of pooled prevalence, odds ratio, and weighted mean difference were calculated with a random effects model.

RESULTS

Of 587 related articles found, six fulfilled the inclusion criteria. Long-term ATD treatment induced a remission rate of 57% [confidence interval (CI) 45-68%], a rate that was higher in adults than in non-adults (61% vs. 53%). The rate of complications was 19.1% [CI 9.6-30.9%], of which only 1.5% were major complications. The annual remission rate for each year of treatment was 16% [CI 10-27%], which was higher in adults than non-adults (19% vs. 14%). However, it should be noted that this is not a true linear correlation, but a positive relationship can be suggested between time and remission rate. Meta-regression revealed that smoking had a significant lowering effect on remission rate.

CONCLUSIONS

Long-term ATD treatment is effective and safe, especially in adults, indicating that it should be considered as an alternative treatment for Graves' disease.

Pediatric Graves' disease: management in the post-propylthiouracil Era

The most prevalent cause of thyrotoxicosis in children is Graves’ disease (GD), and remission occurs only in a modest proportion of patients. Thus most pediatric patients with GD will need treatment with radioactive iodine (RAI; ¹³¹I) or surgical thyroidectomy. When antithyroid drugs (ATDs) are prescribed, only methimazole (MMI) should be administered, as PTU is associated with an unacceptable risk of severe liver injury. If remission does not occur following ATD therapy, ¹³¹I or surgery should be contemplated. When ¹³¹I is administered, dosages should be greater than 150 uCi/gm of thyroid tissue, with higher dosages needed for large glands. Considering that there will be low-level whole body radiation exposure associated with ¹³¹I, this treatment should be avoided in young children. When surgery is performed near total or total-thyroidectomy is the recommended procedure. Complications for thyroidectomy in children are considerably higher than in adults, thus an experienced thyroid surgeon is needed when children are operated on. Most importantly, the care of children with GD can be complicated and requires physicians with expertise in the area.

Thyroid peroxidase autoantibodies are associated with a lesser likelihood of late reversion to hyperthyroidism after successful non-ablative treatment of Graves' disease in Croatian patients

BACKGROUND

Thyroid peroxidase autoantibodies (TPOAbs) are frequently observed in Graves' disease (GD) and tend to persist in patients even after successful treatment with antithyroid drugs. However, there is a lack of consistent data regarding the prognostic significance of TPOAbs during and after non-ablative treatment for Graves' hyperthyroidism.

AIM

To assess the prognostic value of TPOAbs on the long-term outcome of GD patients, who were in remission after the use of antithyroid drugs (block-and-replace regimen).

SUBJECTS

100 remitters were retrospectively investigated for factors associated with the 5-year course of disease recurrence and compared to 60 age/sex-matched patients with intractable GD.

RESULTS

Mild hyperthyroidism, low baseline thyroid-stimulating antibodies levels, and small goiters were predictive of remission. Once attained, the remission was shorter in younger patients, patients with declining post-treatment TSH values, and negative baseline TPOAb levels. The 5-year cumulative incidence of relapse incrementally increased from 24 to 44 to 70 % across decreasing TPOAb tertiles (log-rank, p = 0.00056; the lower tertile representing TPOAb-negative cases). The age-of-onset (p = 0.034), and the baseline TPOAb value [upper tertile, hazard ratio (HR) 0.25; 95 % confidence interval, 0.11-0.59; p = 0.0014; middle tertile, HR 0.47 (0.24-0.9); p = 0.024; Cox regression] were inversely associated with late (>12 months) relapse rates in a level-dependent manner. In contrast, serum logTSH measured 6 months after drug discontinuation was inversely associated with hazard rates at all time points (p = 0.0005).

CONCLUSION

Baseline TPOAb positivity is an independent indicator of long-term remission in GD patients who have been successfully treated, but the mechanism of action and causal relations remain unknown.

Clinical review: Clinical utility of TSH receptor antibodies

CONTEXT

TSH receptor antibodies (TRAb) cause Graves' disease (GD) hyperthyroidism. Widely available TRAb measurement methods have been significantly improved recently. However, the role of TRAb measurement in the differential diagnosis of hyperthyroidism, the prediction of remission of GD hyperthyroidism, the prediction of fetal/neonatal thyrotoxicosis, and the clinical assessment of Graves' ophthalmopathy (GO) are controversial.

EVIDENCE ACQUISITION

We reviewed and analyzed the literature reporting primary data on the clinical use of TRAb. We focused our analyses on clinical studies analyzing third-generation TRAb assays.

EVIDENCE SYNTHESIS

The performance of TRAb in the differential diagnosis of overt hyperthyroidism is excellent, with sensitivity and specificity in the upper 90%. TRAb can accurately predict short-term relapses of hyperthyroidism after a course of antithyroid drugs but are less effective in predicting long-term relapses or remissions. Pregnancies in women with GD with negative TRAb are highly unlikely to result in fetal hyperthyroidism, whereas high titers of TRAb in pregnancy require careful fetal monitoring. GD patients with GO frequently have high TRAb levels. However, there are insufficient data to use the test to predict the clinical course of GO and response to treatment.

CONCLUSIONS

Third-generation TRAb assays are suitable in the differential diagnosis of hyperthyroidism. In GD, TRAb should be tested before deciding whether methimazole can be stopped. TRAb should be used in pregnant women with GD to assess the risk of fetal thyrotoxicosis. The use of TRAb in GO requires further studies.

Is the measurement of inferior thyroid artery blood flow velocity by color-flow Doppler ultrasonography useful for differential diagnosis between gestational transient thyrotoxicosis and Graves' disease? A prospective study

OBJECTIVE

To determine the role of peak systolic velocity, end-diastolic velocity and resistance indices of both the right and left inferior thyroid arteries measured by color-flow Doppler ultrasonography for a differential diagnosis between gestational transient thyrotoxicosis and Graves' disease during pregnancy.

METHODS

The right and left inferior thyroid artery-peak systolic velocity, end-diastolic velocity and resistance indices of 96 patients with thyrotoxicosis (41 with gestational transient thyrotoxicosis, 31 age-matched pregnant patients with Graves' disease and 24 age- and sex-matched non-pregnant patients with Graves' disease) and 25 age and sex-matched healthy euthyroid subjects were assessed with color-flow Doppler ultrasonography.

RESULTS

The right and left inferior thyroid artery-peak systolic and end-diastolic velocities in patients with gestational transient thyrotoxicosis were found to be significantly lower than those of pregnant patients with Graves' disease and higher than those of healthy euthyroid subjects. However, the right and left inferior thyroid artery peak systolic and end-diastolic velocities in pregnant patients with Graves' disease were significantly lower than those of non-pregnant patients with Graves' disease. The right and left inferior thyroid artery peak systolic and end-diastolic velocities were positively correlated with TSH-receptor antibody levels. We found an overlap between the inferior thyroid artery-blood flow velocities in a considerable number of patients with gestational transient thyrotoxicosis and pregnant patients with Graves' disease.

CONCLUSIONS

This study suggests that the measurement of inferior thyroid artery-blood flow velocities with color-flow Doppler ultrasonography does not have sufficient sensitivity and specificity to be recommended as an initial diagnostic test for a differential diagnosis between gestational transient thyrotoxicosis and Graves' disease during pregnancy.

The role of TSH receptor antibodies in the management of Graves' disease

The central role of thyrotropin receptor antibodies (TRAbs) in the pathogenesis of Graves' disease has been recognised for several decades. However, the practical application of testing for TRAbs in clinical decision making remains the subject of controversy. The diagnosis of Graves' disease can be made in most cases simply based on a patient's clinical presentation. The TRAb test is therefore of most value in ambiguous clinical scenarios such as in the differential diagnosis of unilateral exophthalmos, euthyroid Graves' ophthalmopathy, subclinical hyperthyroidism, thyrotoxicosis associated with hyperemesis gravidarum, amiodarone-induced thyrotoxicosis and painless thyroiditis. It may also have a role in predicting the risk of a recurrence of Graves' disease following a course of antithyroid drug treatment. One further clinical utility of the TRAb test is in pregnancy where antibody titre measured during the third trimester is used to predict the risk of neonatal thyroid dysfunction. The TRAb titre not only aids in clinching a difficult diagnosis but can also help guide treatment in some patients. Although the TRAb assay has become more affordable in recent years, cost remains an important factor when considering its use routinely. Nonetheless, this is an underutilised blood test that could augment standard endocrine investigations in the differential diagnosis of hyperthyroidism.

Assays for thyroid-stimulating antibodies and thyrotropin-binding inhibitory immunoglobulins in children with Graves' disease

Studies on thyrotropin receptor autoantibodies (TRAb) by measurement of both thyroid-stimulating antibodies (TSAb) and thyrotropin-binding inhibitory immunoglobulins (TBII) in serum from children with Graves' disease are limited in number of studies. The aim of this study was to investigate the levels of serum TSAb and TBII in children with Graves' disease, and to evaluate the clinical significance of these antibodies. We measured the serum TSAb and TBII at diagnosis and during management in 65 children with Graves' disease. Patients were divided into four groups according to their metabolic state: those with untreated active Graves' disease, those receiving treatment with antithyroid drugs, those in remission, and those in relapse. At diagnosis, both TSAb and TBII assays had high sensitivities and high specificities. In follow-up, the levels of both TSAb and TBII paralleled the course of the disease. There was a strong positive correlation between TSAb and TBII. TBII levels were significantly higher in the patients with ophthalmopathy than those without ophthalmopathy in untreated Graves' children. It was concluded that TSAb and TBII measurements are valuable in the diagnosis and management of children with Graves' disease.

[Evaluation of the medical treatment of Graves' disease (GD)]

The treatment of Graves' disease (GD) with antithyroid drugs (ATD) leads to remission of the disease in approximately half of patients treated for at least six months, and the overall relapse rate is high, ranging from 60% to 80%. The presence of prognostic features for achieving a remission after medical treatment is a matter of discussion in the literature. The aim of this study is to evaluate the effect of different ATD regimens available in Brazil (propylthiouracil--PTU and methimazole--MMI) on remission and relapse rates of GD, as well as to determine possible predictors of remission and relapse of the disease and the side effects profile. We reviewed the records from all patients submitted to medical treatment of GD (and with no report of prior treatment of the disease) for at least six months and followed for at least 12 months after the drug withdrawal at Hospital Universitário Clementino Fraga Filho (HUCFF), between October 1978 and August 2003. We identified 127 patients, with the age ranging from 18 to 88 years (mean 39.3 +/- 12.8). Remission was observed in 58 patients (45.7%) and relapse occurred in 31 (53.4%), at a mean period of 14.5 +/- 16.1 months. We verified that the duration of symptoms before the beginning of medical treatment, age and gender did not influence the rate of remission and the relapse risk, whereas the presence of large goiter size (> 40 grams), Graves' ophthalmopathy and use of high daily doses of ATD (> or = 600 mg of propylthiouracil/60 mg of methimazole MMI) were associated with a decreased remission rate. Moreover, patients who presented a TSH measurement < 0.4 microIU/mL between 4 to 5 weeks after the drug withdrawal showed an increased relapse cumulative probability. In conclusion, our results confirms that lasting remission rate of GD treated with ATD is relatively low. We concluded that the combination of goiter size > 40 g, ophthalmopathy, and use of daily doses of PTU > or = 600 mg or MMI > or = 60 mg was vigorously related to lack of remission of GD. Furthermore, TSH measurement between 4 to 5 weeks after the drug withdrawal seems to be a useful tool to determine the remission chance and the relapse risk of the disease.

Thyrotropin receptor autoantibodies (TSHRAbs): epitopes, origins and clinical significance

Epitopes for > 95% stimulating thyrotropin receptor autoantibodies (TSHRAbs) causally implicated in Graves' disease (Basedow's disease or primary hyperthyroidism) have been identified on on the N-terminal portion of the TSHR extracellular domain, residues 8-165. If the stimulating TSHRAb activity is solely dependent on this region, it is termed homogeneous; if its activity is only largely related to this region, it is termed heterogeneous. The presence of a heterogeneous stimulating TSHRAb in a patient is associated with rapid responses to propylthiouracil or methimazole and may be predictive of long term remission with these oral immunosuppressives. Epitopes for two different Graves' autoantibodies that inhibit TSH binding, TSH binding inhibition immunoglobulins or TBIIs, have also been identified on this region of the TSHR. They do not increase cAMP levels, although one may activate the inositol phosphate, Ca++, arachidonate release signal system. The epitope of blocking TSHRAbs with the ability to inhibit TSH binding (TBII activity), TSH activity, and stimulating TSHRAb activity, and that are causally implicated in the primary hypothyroidism of patients with idiopathic myxedema or some patients with Hashimoto's disease have, in contrast, been largely identified largely on the C-terminal portion of the TSHR extracellular domain, residues 270-395. They have been implicated as important in pregnancy where they attenuate the signs and symptoms of Graves' hyperthyroidism. The appearance of these blocking TSHRAbs during pregnancy in Graves' patients might cause overt or occult hypothyroidism, with resultant effects on fetal development and postnatal intelligence levels. The different TSHRAbs can exist in the same patient at any moment in time, potentially making disease expression a sum of their activities. Assays taking advantage of the epitope mapping findings enable us to detect individual TSHRAbs within a single patient and to better understand their clinical significance.

Graves disease in childhood: a review of the options for diagnosis and treatment

While diagnosing Graves disease in childhood and adolescence does not usually present specific problems, the treatment of hyperthyroidism is still controversial. In particular, with regard to the use of radioiodine therapy, strategies vary between many European and North American pediatric endocrinology centers. After the diagnosis is made, antithyroid drug treatment with methimazole (thiamazole), carbimazole, or propylthiouracil should be performed with caution, in particular, because of severe adverse effects, such as agranulocytosis or hepatitis, that are found in up to 1% of patients. Antithyroid drug treatment should not be continued long-term, particularly since definitive remission cannot be expected in more than 30-40% of patients. In contrast, the risk of severe adverse effects is still present, and the risk of thyroid carcinoma increases with time and appears to be considerably higher than after radioiodine treatment. To a great extent, the success of surgery depends on the skills of a trained surgeon. The question of whether to perform total or subtotal thyroidectomy is yet to be resolved. Surgery should be considered in patients with a large thyroid gland (>80g), severe ophthalmopathy, and a lack of remission on antithyroid drug treatment. Success rates have increased to up to 97%, while severe adverse effects (laryngeal nerve palsy, hypoparathyroidism) occur in approximately 4% of patients. Mortality is below 0.1%. Radioiodine treatment in children >5 years of age does not appear to be associated with an increased risk of thyroid carcinoma; however, long-term data are lacking. Compared with the surgical approach, success rates are lower, particularly if low doses of radioiodine are used. In general, adverse effects are less prevalent than in patients who have undergone surgery.

Epitope heterogeneity of thyroid-stimulating antibodies predicts long-term outcome in Graves' patients treated with antithyroid drugs

Differences in the epitopes of thyroid-stimulating antibodies (TSAbs) from patients with untreated Graves' disease were compared with long-term response to antithyroid drugs. Epitopes were measured using Chinese hamster ovary cells transfected with wild-type human TSH receptor (TSHR) and two receptor chimeras, wherein TSHR residues 9-165 or 90-165 had been substituted with comparable residues of the LH/chorionic gonadotropin receptor. Of 159 patients studied, 52 (32.7%) exhibited positive TSAb activity with one or both chimera lines (heterogeneous group), and 107 (67.3%) had no activity with either (homogeneous group). Independent of all other parameters, patients with heterogeneous epitopes responded more favorably to oral antithyroid drugs than patients with homogeneous epitopes (65.4% vs. 41.9%, P = 0.011: estimated odds ratio by logistic regression, 2.17). Although most clinical parameters were not different at presentation, significant differences in the size of goiters, total T(3) concentrations, and titers of TSH-binding inhibitory Igs were evident in the successfully treated group (n = 80) by comparison to the group of patients whose treatment failed (n = 79). Alone, these three parameters did not predict outcome; however, when either of these parameters were considered together with epitope heterogeneity, predictability of a positive therapeutic response was increased to nearly 80%. Thus, the presence of TSAbs with a heterogeneous epitope in a patient with Graves' disease is not only associated with a favorable response to antithyroid drug treatment, it may help predict the response to treatment when the patient is initially seen.

Detection of low titre TBII in patients with Graves' disease using recombinant human TSH receptor

OBJECTIVES

We evaluated thyrotropin-binding inhibitor immunoglobulin (TBII) in sera from patients with Graves' disease (GD) by using the new human recombinant TSH receptor (TSH-R) assay to determine if it is useful for the diagnosis and follow-up of GD.

PATIENTS

Serum samples from 25 patients with untreated GD, 24 with relapsing GD, 15 with GD in remission and 197 treated GD patients were examined. TBII was also measured in sera from healthy individuals (n = 69).

DESIGN AND MEASUREMENTS

TBII was retrospectively measured by using the conventional porcine TBII assay (pTBII) and the human recombinant TBII assay (hTBII). Specificity was adjusted at 97.5% for both assays by receiver-operating characteristic (ROC) plot analysis, resulting in cut-offs at 10.5% inhibition (hTBII) and 9.9% (pTBII). Sensitivity was 87% for hTBII compared to 52% for pTBII (P < 0.0001).

RESULTS

Even in pTBII-positive patients, hTBII values (57.6 +/- 26.1%) were significantly (P < 0.0001) higher than pTBII values (34.2 +/- 27.6%). When 139 pTBII-negative serum samples from patients with treated GD were examined, 97 samples (69.8%) were positive for hTBII. hTBII values (23.9 +/- 17.0%) were significantly (P < 0.0001) higher than pTBII values (4.1 +/- 3.3%). hTBII was positive in 13 of 13 patients who were taking antithyroid drugs but had normal serum TSH levels. When 19 serum samples from pTBII-negative untreated patients with GD were examined, 15 out of 19 (79%) were positive for hTBII. We also examined 24 patients with relapsing GD. hTBII was positive in 16 (64%) patients, whereas seven (16%) were positive for pTBII (P < 0.01). Positivity of hTBII in these untreated or relapsing GD patients was significantly higher than that of thyroid stimulating antibodies. We then examined TBII levels in 15 patients with GD in remission who had normal serum TSH values. hTBII was positive in seven patients at the time of blood withdrawal, and GD subsequently relapsed in three hTBII-positive patients in 6 months.

CONCLUSIONS

Low TBII titres can now be followed more accurately during the course of treatment, which will also allow better longitudinal studies on the importance of TBII for the diagnosis as well as the prognosis of GD with respect to remission or relapse.

Thyrotoxicosis due to metastatic papillary thyroid cancer in a patient with Graves' disease

Thyrotoxicosis resulting from functional thyroid cancer metastases is extremely rare, and is mostly caused by follicular cancer. The lesions causing thyrotoxicosis are usually bulky and extensive. We report here a patient with Graves' disease and concomitant papillary thyroid cancer who developed metastases causing symptomatic thyrotoxicosis. His serum titers of thyroid stimulating Ig (TSIs) were elevated. We believe that TSIs were responsible for thyrotoxicosis by stimulating hormonogenesis in the metastatic lesions.

Thyroid autoantibodies

The characteristics of thyroid autoantibodies are reviewed and new assays for the autoantibodies described, in particular point of care (POC) tests for thyroid peroxidase (TPO) autoantibodies and for thyroglobulin (Tg) autoantibodies. These POC tests depend on the ability of the autoantibodies to inhibit gold labelled human monoclonal antibodies binding to TPO or to Tg. The POC tests show similar sensitivity and specificity to conventional ELISA for the autoantibodies. A new ELISA to measure autoantibodies to the TSH receptor (TRAb) is described, is based on TSH receptor coated onto plate wells by way of a monoclonal antibody. Comparison of porcine and human TSH receptors indicates that there is no advantage in using human TSHR in assay systems based on competition between TRAb and bovine or porcine TSH for immobilised TSHR. In terms of the origins of Graves' disease, it is speculated that this most common overt autoimmune disease in man might have occurred first when Homo sapiens sapiens migrated rapidly out of Africa about 100,000 years ago.

Autoimmune thyroid disease: new models of cell death in autoimmunity

Autoimmunity to thyroid antigens leads to two distinct pathogenic processes with opposing clinical outcomes: hypothyroidism in Hashimoto's thyroiditis and hyperthyroidism in Graves' disease. The high frequency of these diseases and easy accessibility of the thyroid gland has allowed the identification of key pathogenic mechanisms in organ-specific autoimmune diseases. In early investigations, antibody- and T-cell-mediated death mechanisms were proposed as being responsible for autoimmune thyrocyte depletion. Later, studies on apoptosis have provided new insights into autoimmune target destruction, indicating the involvement of death receptors and cytokine-regulated apoptotic pathways in the pathogenesis of thyroid autoimmunity.

Importance of the Detection Method for Thyroglobulin Antibodies for the Validity of Thyroglobulin Measurements in Sera from Patients with Graves Disease

Background: The use of recovery tests has been proposed to disclose interferences from anti-thyroglobulin antibodies (TgAbs) in thyroglobulin (Tg) assays. We studied the value of a recovery test in Tg measurement by a new commercial IRMA.

Methods: Blood samples were collected from 153 patients with untreated Graves disease. Tg and TgAbs were measured by IRMA and RIA, respectively (Dynotest Tg-plus and Dynotest anti-Tgn; Brahms Diagnostica). The recoveries of added amounts of Tg were calculated for each serum.

Results: TgAbs were detected in 72 of the 153 patients (47%). The recovery test results for the 81 TgAb-negative sera (median, 101%; range, 80–115%) were identical to the results for the 91 controls (median, 102%; range, 80–124%). By contrast, significantly lower recovery test results were observed for the 72 TgAb-positive sera (median, 79%; range, 60–103%; Z = −8.363; P &lt;0.0001). In the 34 of the 72 TgAb-positive sera with a normal recovery test, Tg concentrations were significantly lower (median Tg, 13.6 μg/L; range, 1.1–360 μg/L) than those measured in the TgAb-negative sera (median, 107 μg/L; range, 1.2–700 μg/L; Z = −3.797; P &lt;0.0001).

Conclusions: Tg values were decreased in TgAb-positive sera even when the results of the recovery tests were normal. This test should not be used alone to determine the validity of a serum Tg measurement in Graves disease.

TSH-receptor antibody measurement for differentiation of hyperthyroidism into Graves' disease and multinodular toxic goitre: a comparison of two competitive binding assays

OBJECTIVES

Graves' disease is characterized by stimulating autoantibodies to the TSH-receptor (TRAb). The aim of this study was to compare the performance of a new TRAb assay based on competitive binding to recombinant human TSH-receptors (H-TRAb) with an assay employing purified porcine TSH-receptors (P-TRAb). Furthermore, to evaluate the applicability of the H-TRAb assay to discriminate between patients with hyperthyroidism due to Graves' disease (GD) and multinodular toxic goitre (MNTG).

DESIGN AND MEASUREMENTS

H-TRAb and P-TRAb were measured in patients with newly diagnosed hyperthyroidism due to GD (n = 106) and MNTG (n = 94). For comparison, TRAb was measured in patients with primary autoimmune hypothyroidism, euthyroid subjects with an enlarged thyroid gland by ultrasound, and healthy controls (n = 100 for each group). Patients were consecutively included from a population survey.

RESULTS

If the cut-off values recommended by the manufacturer for TSH-receptor antibody positivity were used for evaluation, the sensitivity of the H-TRAb assay vs. the P-TRAb assay in diagnosing GD was: 95.3/67.9% (P < 0.001). Specificity was (H/P-TRAb): 99/99%. The sensitivity of P-TRAb was increased if the upper 97.5% limit of measurements in controls was used as cut-off (H-TRAb vs. P-TRAb: 95.3/80.2%, P < 0.001). Specificity (H/P-TRAb): 98/98%. The difference between assay performance may partly be due to a better technical performance of the H-TRAb assay with more reliable results in the low range of measurements. However, even in GD patients with clearly measurable TRAb, 25% had a P-TRAb < 50% of the value expected from the H-TRAb measurement. This suggests that a subgroup of patients produce TRAb with a higher affinity for the human than the porcine TSH receptor. A relatively high proportion of patients with MNTG were TRAb positive (H-TRAb/P-TRAb: 17/9%). Characteristics of H-TRAb positive and negative MNTG patients were compared. There was no difference between size of thyroid gland and number of nodules by ultrasonography. H-TRAb positive patients had significantly higher serum T4 and T3 and a greater number were TPO-Ab positive.

CONCLUSIONS

H-TRAb diagnosed Graves' disease with a high sensitivity and specificity than P-TRAb. The high occurrence of TRAb in multinodular toxic goitre might in part reflect an overlap between Graves' disease and multinodular toxic goitre in some patients.

Clinical value of a new TSH binding inihibitory activity assay using human TSH receptors in the follow-up of antithyroid drug treated Graves' disease. Comparison with thyroid stimulating antibody bioassay

First, to evaluate the performance level of a new TSH binding inhibitory antibody assay using human recombinant TSH receptors (h-TBII) in comparison with a thyroid stimulating antibody (TSAb) bioassay performed before, at the end of treatment (18 months) and after antithyroid drug withdrawal in Graves' disease patients; second, to assess the accuracy with which h-TBII levels could predict relapse and remission. Retrospective study on serum samples of Graves' disease patients treated by antithyroid drugs for 18 months. Serum samples from 140 patients (27 men and 113 women; median age 42 years) with recent onset hyperthyroidism due to Graves' disease were retrospectively tested for h-TBII at diagnosis, at 18 months and for 76 of them 6, 12, 24 and 36 months after drug withdrawal or at relapse. TSAb were also evaluated at each time. Thyroid blocking antibodies (TBAb) were measured in sera positive for h-TBII and negative for TSAb. h-TBII levels were measured with a radioreceptor assay using the human recombinant TSH receptor (DYNOtest TRAK human from B.R.A.H.M.S. Diagnostica, Berlin, Germany). TSAb and TBAb levels were assayed in thyrocyte cultures. At diagnosis, high levels of h-TBII were found in 138 of 140 patients with Graves' disease (98.6%). High TSAb values were also detected in the same 138 patients. The h-TBII and TSAb values were significantly correlated (r = 0.582, p < 0.0001). At 18 months, h-TBII were found in 48 of the 140 patients (34%) and TSAb in 43 patients (31%). The h-TBII and TSAb values were significantly correlated (r = 0.618, p < 0.0001) and fell significantly between diagnosis and 18 months (Z = - 9.84, p < 0.0001 and Z = - 9.19, p < 0.0001). TBAb were found in two of the 11 sera positive for h-TBII and negative for TSAb. At diagnosis, the median levels of h-TBII and TSAb were not significantly different between the patients who relapsed within the 3 years after the withdrawal of treatment (n = 60) and those who did not (n = 80) (Z = - 1.1, ns; Z = - 0.216, ns). At 18 months, the prevalences of h-TBII and TSAb were significantly increased in patients who relapsed compared to those who remained in remission at 3 years (60% vs. 15%, chi2 = 30.8, p < 0.0001 and 55% vs. 13%, chi2 = 29.1, p < 0.0001, respectively). h-TBII and TSAb median levels were also significantly increased in patients who relapsed compared to the others (Z = - 4,8, p < 0.0001; Z = - 3,01, P < 0.005). Among the 60 patients who relapsed, 36 (60%) displayed h-TBII and 33 (55%) TSAb at 18 months. The majority of patients who relapsed during the 2 years following the end of treatment, in contrast to those who relapsed later, were positive for h-TBII (67% vs. 27%, chi2 = 6.01, p = 0.035). Seventeen of the 18 tested patients who relapsed were negative for h-TBII at 18 months, were then positive for h-TBII at the time of relapse, whereas 15 of them were still negative, 6-12 months before the relapse. Among the 80 patients who remained in remission at 3 years, only 10 (13%) displayed TSAb and 12 (15%) h-TBII at 18 months. In 10 of these 12 patients who were further evaluated for h-TBII positivity, h-TBII fell to control levels during the 3 years following the end of treatment. The new h-TBII assay is a simple and rapid method with a performance level similar to that of TSAb determination. Its sensitivity is close to 100% at diagnosis. In the whole group, TBII level analysis is relevant as a predictor for short time relapse. However, some of the patients are "misclassified", due to the inter-individual variability in the time course of h-TBII activity. Our results confirm that, in addition to h-TBII, even when measured with a highly sensitive test, the concomitant analysis of other clinical and/or biological parameters is necessary to improve the prediction of treatment outcome.

The interaction of TSH receptor autoantibodies with 125I-labelled TSH receptor

Detergent-solubilized porcine TSH receptor (TSHR) has been labeled with 125I using a monoclonal antibody to the C-terminal domain of the receptor. The ability of sera containing TSHR autoantibody to immunoprecipitate the labeled receptor was then investigated. Sera negative for TSHR autoantibody (as judged by assays based on inhibition of labeled TSH binding to detergent-solubilized porcine TSHR) immunoprecipitated about 4% of the labeled receptor, whereas sera with high levels of receptor autoantibody immunoprecipitated more than 25% of the labeled receptor. The ability to immunoprecipitate labeled TSHR correlated well with ability of the sera to inhibit labeled TSH binding to the receptor (r = 0.92; n = 63), and this is consistent with TSHR autoantibodies in these samples being directed principally to a region of the receptor closely related to the TSH binding site. Preincubation of labeled TSHR with unlabeled TSH before reaction with test sera inhibited the immunoprecipitation reaction, providing further evidence for a close relationship between the TSHR autoantibody binding site(s) and the TSH binding site. This was the case whether the sera had TSH agonist (i.e., thyroid stimulating) or TSH antagonist (i.e., blocking) activities, thus, providing no clear evidence for different regions of the TSHR being involved in forming the binding site(s) for TSHR autoantibodies with stimulating and with blocking activities. The ability of TSHR autoantibodies to stimulate cyclic AMP production in isolated porcine thyroid cells was compared with their ability to immunoprecipitate labeled porcine TSHR. A significant correlation was observed (r = 0.58; n = 50; P < 0.001) and the correlation was improved when stimulation of cyclic AMP production was compared with inhibition of labeled TSH binding to porcine TSHR (r = 0.76). Overall, our results indicate that TSHR autoantibodies bind principally to a region on the TSHR closely related to the TSH binding site, and this seems to be the case whether the autoantibodies act as TSH agonists or antagonists.