Tg Autoantibodies Research Articles

Influence of Thyroglobulin (Tg) Autoantibodies on Tg levels Measured by Different Methodologies: (IMA, LC-MS/MS and RIA).

Serum thyroglobulin (Tg) measured by Immunometric assays (IMA) is prone to underestimation due to Tg autoantibody (TgAb) interference, often prompting reflex Tg measurement by liquid chromatography/tandem mass spectrometry (MS) or radioimmunoassay (RIA). IMA, MS and RIA methodologies were used to measure serum Tg in TgAb-negative (TgAb-) and TgAb-positive (TgAb+) patients with either distant metastatic thyroid cancer (DTC) or hyperthyroidism (HY) - patients in whom a detectable serum Tg would be expected. 1) Between-method Tg variability necessitates method continuity when monitoring the Tg trends of TgAb- DTC patients. 2) The presence and concentration of TgAb appeared to have a lowering effect on serum Tg measured by all methodologies (IMA, MS and RIA). 3) Since the reliability of Tg measured in the presence of TgAb is often uncertain, the TgAb trend (measured by the same method) may be a useful surrogate DTC tumor marker.

Challenges and current advances in the methodology of thyroglobulin measurements.

Thyroglobulin (Tg) is a large protein secreted exclusively by the thyroid gland. In a clinical setting, it is measured for the purpose of follow-up of thyroidectomy patients. However, Tg measurements are often impeded by the presence of Tg autoantibodies and/or heterophylic antibodies that interfere with most measuring platforms. This presents a global problem in thyroid cancer patients who need to be postoperatively monitored for recurrent or residual disease. Therefore, in this paperwe offer an overview of the existing methodologies and alternative approaches for Tg measurements that are afocus of research worldwide. These includeTg mRNA measurements, exosomal Tg detection, the use of alternative analytes (liquid biopsies) and the development of new approaches for preanalytical sample treatment.

Study of thyroid disorders in vitiligo.

Vitiligo, an acquired sometimes familial depigmentary disorder of the skin and hair that results from selective destruction of melanocytes or pigment cells. It is the single most important non-neo plastic disease that involves both the immune system and melanocytes which are subsequently destroyed and the affected area turns pale and becomes white. The prevalence of the disease is between 1% and 2% in general population. It is a prospective, randomized, and controlled study. Over 90 vitiligo patients attending Dermatology OPD and vitiligo clinic are enrolled in the study. About 35 apparently healthy, age and sex matched individuals are selected to serve as control. A prescribed proforma containing all the demographic data, relevant questionnaire were recorded for each and every case with brief clinical history suggestive of any thyroid disease as well as those referred by the clinicians. P value <0.05 is considered significant. The Quantitative Determination of Thyroglobulin (Tg) Autoantibodies in Human Serum or Plasma by a Microplate Enzyme Immunoassay. Vitiligo group, thirty four (37.78%) patients have clinical hypothyroidism while 9 (10%) patients have clinical hyperthyroidism. This difference in the distribution is statistically significant (P < 0.05) with a Chi-square value of 10.08. The data are entered, analyzed and computed with SPSS version 15 software and well-known statistical test like Chi-square, students' 't' test have been advocated wherever found applicable. P value <0.05 is considered significant. There is increased incidence of autoimmune thyroid diseases among vitiligo patients. The reason being vitiligo usually precedes the onset of thyroid dysfunction.

Prevalence of Thyroglobulin Antibody (TgAb) Positivity in Patients Post Treatment for Differentiated Thyroid Carcinoma and Verification of Serum Thyroglobulin Measurements by Thyroglobulin Recovery Test and TgAb assay

Introduction: Thyroglobulin (Tg) measurement is important for detection of disease recurrence in patients with differentiated thyroid carcinoma (DTC). However, its measurement is affected by Tg autoantibodies (TgAb). Calculation of Tg recovery may complement quantitative TgAb measurement in detection of interference. This study aimed to determine the prevalence of TgAb positivity in Tg samples received from post-thyroidectomy DTC patients in Hospital Pulau Pinang (HPP). Additionally, we assessed the use of the Tg II Confirmatory Test (Roche Diagnostics) assay to calculate Tg recovery in detecting Tg assay interference. Method: Samples received for Tg measurements from post-thyroidectomy DTC patients with TgAb positivity were tested with Tg II Confirmatory Test. The Tg levels [categorised as biochemically detectable (≥1.0 μg/l) vs biochemically undetectable (&lt;1.0 μg/l)], TgAb and Tg recovery [categorised as correct (70%-130%) vs compromised (&lt;70% and &gt;130%) recovery] were interpreted with the diagnostic radioiodine uptake (RAI) results. Results: In this study, 58/73 (79.5%) samples with TgAb positivity had undetectable Tg. A compromised Tg recovery was observed in three (4.1%) samples. Only 51 out of 73 subjects had an RAI performed, out of which 27 (52.9%) had increased RAI uptake (radiological evidence of persistent/recurrent disease). Of those with increased RAI uptake, 17 (63%) had biochemically undetectable Tg, out of which none had compromised Tg recovery. Conclusion: The presence of TgAb prevents reliable measurement of Tg. The Tg II Confirmatory assay for calculation of Tg recovery did not provide additional complementary value to quantitative TgAb measurement in the detection of interference in Tg measurements.

Clinical irrelevance of lower titer thyroglobulin autoantibodies in patients with differentiated thyroid carcinoma.

Thyroglobulin (Tg) is an established tumor marker for differentiated thyroid carcinoma (DTC) patients. However, Tg immunoassays can be subject to Tg autoantibody (TgAb) interference resulting in incorrect Tg values. Therefore, Tg measurement with liquid chromatography-tandem mass spectrometry (LC-MS/MS) could be promising in patients with TgAbs. In this study, we compared Tg IRMA and Tg-LC-MS/MS analytically in the presence of TgAbs. Furthermore, we compared the clinical interpretation of results obtained by both Tg assays in DTC patients with lower TgAbs titers (<10 U/mL) during 131I ablation therapy. Totally 118 DTC patients diagnosed between 2006 and 2014 in a University Medical Center were followed with the Tg-IRMA (Thermo Fischer Scientific) and ARCHITECT anti-Tg (Abbott Laboratories) assays. We re-analyzed their samples with a sensitive Tg-LC-MS/MS method (Labcorp, limit of quantification of 0.02 ng/mL). Passing-Bablok regression analysis was performed on samples obtained during 131I ablation therapy and follow-up. In 304 samples with lower TgAb titers, a good analytical agreement was found between both Tg assays (slope of 1.09 (95% CI: 1.05-1.16)). Fifty-five samples with potentially interfering TgAbs showed higher Tg-LC-MS/MS values than Tg-IRMA (slope of 1.45 (95% CI: 1.12->>100)). In patients(n = 91) with lower TgAb titers at the time of 131I ablation therapy, the Tg assays showed a clinical concordance of 91.2, 87.9, and 98.9%, respectively, using a Tg cut-off value of 1.0, 2.0, and 5.0 ng/mL. In DTC patients with lower titer TgAbs, Tg-IRMA is still a reliable and useful tumor marker. In DTC patients with potentially interfering TgAbs, Tg-IRMA values decreased due to TgAb interference.

SCREENING OF THYROID AUTOANTIBODIES ANTI-TG, ANTI-TPO AND ITS CORRELATION WITH CLINICAL THYROID DISEASES IN VITILIGO IN THE NORTH-EASTERN REGION OF INDIA

Background and aims: Vitiligo is an acquired sometimes familial depigmentary disorder of the skin and hair that results from selective destruction of melanocytes or pigment cells. It is the single most important non-neo plastic disease that involves both the immune system and melanocytes which are subsequently destroyed and the affected area turns pale and becomes white. The precise cause of vitiligo is complex but some evidences are always suggesting that it is caused by a combination of autoimmune, genetic and environmental factors. Over half of the people with vitiligo have acquired some loss of pigment cells before the age of 20 years. The prevalence of the disease is between 1-2% in general population. Therefore, the present study is taken up to evaluate the prevalence of thyroid diseases in vitiligo patients. Methods:It is a prospective, randomized and controlled study. 90 vitiligo patients attending the Dermatology OPD and vitiligo clinic are enrolled in the study. Thirty five apparently healthy, age and sex matched individuals are selected to serve as control. A prescribed proforma containing all the demographic data, relevant questionnaire were recorded for each and every case with brief clinical history suggestive of any thyroid disease as well as those referred by the clinicians.interpretationsare made. P value &lt; 0.05 is considered significant. The Quantitative Determination of Thyroglobulin (Tg) Autoantibodies in Human Serum or Plasma by a Microplate Enzyme Immunoassay. Results:Vitiligo group, thirty four (37.78%) patients have clinical hypothyroidism while 9(10%) patients have clinical hyperthyroidism. This difference in the distribution is statistically significant (P&lt;0.05) with a chi-square value of 10.08. The datas are entered, analysed and computed with SPSS version 15 software and well known statistical test like Chi-square, students t test have been advocated wherever found applicable. The necessary interpretations are made. P value &lt; 0.05 is considered significant. Conclusion:There is increased incidence of autoimmune thyroid diseases among vitiligopatients. Various thyroid antibodies were detected in thyroid disorders, suggesting that these thyroid antibodies could act as sensitive markers for detection of early and subclinical autoimmune disorders of thyroid gland including Graves disease and Hashimotos thyroiditis. The reason beingvitiligo usually precedes the onset of thyroid dysfunction. Therefore, these thyroid autoantibodies specially anti-TPO, anti-TG should be included along with thyroid parameters TSH, T3,T4 in routine investigation of vitiligo, as association of vitiligo with autoimmune thyroid disease is very much common in the North - Eastern region of India.

Seroprevalence of Anti-Thyroglobulin Antibodies in Korea.

The appropriate use of the thyroglobulin (Tg) test involves the concurrent measurement of Tg auto-antibodies (Tg Ab) due to the potential for false low or false high Tg due to Tg Ab interference. We retrospectively reviewed Tg and Tg Ab test results requested from local clinics and hospitals in Korea between July 1, 2020 and June 30, 2021. During the study period, 13,811 Tg tests were performed. Among them, 6,769 Tg tests were identified as being repeatedly measured from 2,988 Korean adults. Among the 6,769 performed Tg tests, 2,733 (40.4%) did not have concurrently performed Tg Ab tests. Among the 2,988 subjects, 1,089 (36.4%) had no concurrently measured Tg Ab test results. Among 4,036 Tg results with concurrently measured Tg Ab, 1,045 (25.9%) had positive Tg Ab results, which could interfere with Tg concentration measurements. The Tg Ab test appears to be underutilized in Korea.

A Novel Thyroglobulin Immunoassay Using the Specimen-Pretreatment Process Improves the Accuracy of Thyroglobulin Measurements in Anti-Thyroglobulin Positive Specimens.

Recently, second-generation thyroglobulin (Tg) sandwich immunoassays have been used in clinical laboratories to measure the serum Tg levels, which is a tumor marker used to monitor postoperative patients with differentiated thyroid cancers. However, these immunoassays are often subject to Tg autoantibody (TgAb) interference. TgAb interference is inevitable for almost all Tg immunoassays, resulting in unreliable Tg measurement values of TgAb-positive samples. To address TgAb interference, we have developed a novel immunoassay based on a fully automated chemiluminescent enzyme immunoassay system using the effective specimen-pretreatment process to inactivate TgAb in blood and evaluated its assay performance. The developed assay was traceable to BCR457 IRMM reference material with a limit of quantification of 0.03 ng/mL. The pretreatment process inactivated almost all TgAb in specimens and allowed accurate Tg measurements in TgAb-positive samples in which TgAb interference was observed using the immunoassays. Size-exclusion chromatography analysis of immunoreactive Tg molecule in a TgAb-positive serum verified disruption of the Tg-TgAb immune complex by the pretreatment process. Good correlation of Tg values in TgAb-negative specimens was observed between the new Tg immunoassay and the second-generation sandwich immunoassays. However, there were numerous discrepant samples on bias plots between the new Tg immunoassay and the second-generation sandwich immunoassays for TgAb-positive specimens. This study indicates the new Tg immunoassay with the specimen-pretreatment process is both robust and free from interference by TgAb. Thus, this novel assay is superior to second-generation sandwich immunoassays and gives accurate Tg concentrations even for TgAb-positive cases.

Test Utilization for Thyroglobulin and Anti-Thyroglobulin Antibody Assays in Korea.

When measuring thyroglobulin (Tg), simultaneous measurement of Tg autoantibodies (Ab) is recommended by clinical guidelines for follow-up of patients with differentiated thyroid cancers after thyroidectomy and radioactive iodine ablation. We aimed to investigate test utilization of Tg and Tg Ab assays in local clinics and hospitals in Korea. We retrospectively reviewed data from the laboratory information system between November 6, 2017 and December 31, 2019. During the study period, 10,551 Tg tests were performed on 2,592 Korean adults from 97 local clinics and hospitals. Among them, 3,924 (37.2%) test results lacked concurrent Tg Ab assays, while 6,627 test results had concurrently measured Tg Ab, and 528 (8.0%) showed positive Tg Ab results, which could interfere with measurement of Tg concentration. The results of this study provide basic information regarding test utilization of Tg Ab assays to improve test utilization for accurate Tg measurement in Korean patients.

Immunoinformatic Analysis of Human Thyroglobulin

Abstract The AutoImmune ThyroiDitis (AITD), known as Hashimoto’s disease, is a chronic autoimmune thyroid disease progressively developed to hypothyroidism. The AITD is characterized by the formation of autoantibodies targeting two specific thyroid antigens, Thyroglobulin (Tg) and Thyroid PerOxidase (TPO). Tg is a precursor of the thyroid hormones while TPO catalyses their synthesis. The AITD has a strong genetic predisposition. During the last years, it was found that the susceptibility to AITD is associated with certain Human Leukocyte Antigens (HLA) class II genes of loci DR and DQ. In the present study, we applied in-house immunoinformatic tools to identify peptides originating from Tg and binding to AITD susceptible alleles: HLA-DR3, HLA-DR4, HLA-DR5, HLA-DQ2 and HLA-DQ8. Five peptide fragments containing promiscuous overlapping binders were selected. These were p470, p949, p1948, p2348 and p2583. Only one of them contains a known epitope (p1948). The rest have not been reported yet. The selected peptide fragments will be coupled to monoclonal antibodies specific to inhibitory B cell receptors designed to suppress the production of Tg autoantibodies.

THE CONCENTRATION OF ANTI THYROGLOBULIN (TGAB) AND ANTI THYROID PEROXIDASE (TPOAB) AUTOANTIBODY IN NON-OBESE DIABETIC PATIENTS

Introduction: Autoimmune diseases are usually systemic. The autoimmune polyendocrine syndrome was defined as a failure of various endocrine glands caused by an autoimmune mechanism. Autoimmune diabetes (type 1 and LADA) is not exceptional, the long-lasting positivity of anti-GAD may increase the risk of developing thyroid autoimmune diseases. Aims: (1) To determine the concentration and the positivity rate of Thyroglobulin autoantibody (TgAb) and TPO autoantibody (TPOAb) on non-obese diabetic patients. (2) To examine the relationship between thyroglobulin autoantibody (TgAb) and TPO autoantibody (TPOAb) to the negative and positive anti GAD autoantibody status and some other factors. Subjects and methods: 85 serum samples of non-obese diabetic patients (BMI &lt; 23) were used to measure the anti GAD autoantibody, anti Tg and anti TPO autoantibody by enzyme-linked immunoassay and electrochemiluminescence immunoassay, at the Hue university hospital. Results: The mean concentration of the TgAb and TPOAb were 1118.35 ± 1583.45 IU/ml and 85.85 ± 42.22 IU/ml, respectively. The positivity rate of the TgAb was 9.4% and the positive rate of the TPOAb was là 14.1%. There was a statistically significant difference in the positivity of the TPO antibody with the presence or absence of the GAD antibody, between the mean concentration of TPO antibody and diabetes detection time and HbA1C concentration between anti-Tg (+), anti-TPO (+) groups and anti-Tg (-), anti-TPO (-) groups. Conclusions: There was a correlation between anti-TPO positivity with non-obese diabetes patients with positive anti-GAD, between diabetes detection time with anti-TPO concentration. In patients with anti-Tg (+), anti-TPO (+), the HbA1C concentration was found higher than those with anti-Tg(-), anti-TPO(-). Keywords: diabetes, non-obese, GAD autoantibody, Tg autoantibody, TPO autoantibody.

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

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

Measuring thyroglobulin in patients with thyroglobulin autoantibodies: evaluation of the clinical impact of BRAHMS Kryptor® Tg-minirecovery test in a large series of patients with differentiated thyroid carcinoma.

Background The present study was undertaken to evaluate the clinical impact of a thyroglobulin (Tg) minirecovery test (Tg-mRec) in a large series of differentiated thyroid carcinoma (DTC) patients treated and monitored homogeneously in a tertiary referral center. Methods Included were 1120 serum samples from 798 DTC patients. Tg, Tg autoantibodies (TgAb) and Tg-mrec measurements were performed on the automated Kryptor® platform and results compared to the corresponding clinical status. Results Among included samples 228 (20%) were TgAb-positive (TgAb+) and 892 (80%) TgAb-negative (TgAb-), respectively. Tg cutoff points were settled at 0.31 μg/L and 0.15 μg/L for TgAb- and TgAb+ patients, respectively, by ROC curve analysis. The diagnostic performance of serum Tg was reduced in TgAb+ compared to TgAb- patients, however, 87% of TgAb+ patients with recurrent disease and, particularly, all patients with distant metastases were correctly detected by adopting an optimized Tg cutoff for TgAb+ patients. A disturbed recovery was found in only 1% of TgAb- patients and in these cases no clinically relevant information was added by the Tg-mRec. Among TgAb+ patients with undetectable Tg and undisturbed Tg-mRec, no one had recurrent disease. However, a falsely undetectable Tg was demonstrated in two patients with recurrent disease who next to increased TgAb also had a disturbed Tg-mRec test. Conclusions There is no additional clinical benefit from performing Tg-mRec in most patients. It can however be considered in TgAb+ patients with undetectable Tg levels as it may help differentiate between patients with true negative and false negative Tg levels in the presence of such antibodies.

Comparison of Serum Thyroglobulin Levels in Differentiated Thyroid Cancer Patients Using In-House Developed Radioimmunoassay and Immunoradiometric Procedures.

Thyroglobulin (Tg) is a proven tumor marker in the follow-up and post-operative management of patients with differentiated thyroid cancer (DTC). All assays for serum thyroglobulin (s-Tg) are based on immunoassays, however, the assay technique has a bearing on the variations seen in the estimations. We studied this using four in-house developed radioimmunoassays (RIA) and immunoradiometric assays (IRMA). Limit of detection, working range, recovery, dilution test, precision profiles and method comparison were evaluated. All four methods were used for the estimation of s-Tg in DTC patients and also compared for their performance using commercially available Tg IRMA kits from DiaSorin and Izotop. The s-Tg values measured by six different immunoassays showed very significant inter-method correlation (0.84-0.99, p < 0.001). However, among the in-house developed assays; the coated tube IRMA showed a better sensitivity and precision at the lower concentration range and hence, is preferable for the routine measurement of s-Tg in patients negative for Tg autoantibodies (TgAb). Although the second generation IRMAs offer practical benefits of having higher sensitivity, shorter turn-around time and convenience of automation, they, unfortunately, also have higher tendency for interference from both TgAb and heterophilic antibodies, if present in the sample. On the contrary, RIA is less prone to such interference and, hence, can be used in patients with TgAb. In order to effectively use this test, it is important that nuclear medicine physicians and endocrinologists understand these intrinsic technical limitations encountered during s-Tg measurement.

Genome-wide meta-analysis identifies novel gender specific loci associated with thyroid antibodies level in Croatians

Autoimmune thyroid diseases (AITD) are multifactorial endocrine diseases most frequently accompanied by Tg and TPO autoantibodies. Both antibodies have a higher prevalence in females and act under a strong genetic influence.To identify novel variants underlying thyroid antibody levels, we performed GWAS meta-analysis on the plasma levels of TgAb and TPOAb in three Croatian cohorts, as well as gender specific GWAS and a bivariate analysis.No significant association was detected with the level of TgAb and TPOAb in the meta-analysis of GWAS or bivariate results for all individuals. The bivariate analysis in females only revealed a genome-wide significant association for the locus near GRIN3A (rs4457391, P = 7.76 × 10−9). The same locus had borderline association with TPOAb levels in females (rs1935377, P = 8.58 × 10−8).In conclusion, we identified a novel gender specific locus associated with TgAb and TPOAb levels. Our findings provide a novel insight into genetic and gender differences associated with thyroid antibodies.

The percentage of serum thyroglobulin rise in the first-week did not predict the eventual success of high-intensity focussed ablation (HIFU) for benign thyroid nodules

Background: Given that high-intensity focussed ultrasound (HIFU) of benign thyroid nodules often causes a massive release of thyroglobulin (Tg) into the circulation, we hypothesised a greater initial Tg rise may result in a greater nodule shrinkage 6 months after ablation.Methods: One hundred and five patients who underwent HIFU for symptomatic benign thyroid nodule from 2015 to 2016 were analysed. Serum Tg and anti-Tg autoantibody were checked on treatment day (baseline) and 4 d after treatment. The % of Tg rise = [serum Tg on day-4 – baseline serum Tg]/[baseline serum Tg] * 100 while the nodule shrinkage as measured by volume reduction ratio (VRR) = [baseline volume – volume at 6-month]/[baseline volume] * 100. Treatment success was defined as VRR >50%.Results: At 6-month, the mean VRR was 62.2 ± 25.0% and 59 (76.6%) patients had treatment success. The mean baseline Tg level increased from 292.8 ± 672.7 ng/mL to 2022.7 ± 1759.8 ng/mL in the first-week. The % of Tg rise did not significantly correlate with either 3-month or 6-month VRR (p = 0.920 and p = 0.699, respectively). The mean % of Tg rise in the first week was not different between those with and without 6-month treatment success (368.2% vs. 1068.7%, p = 0.381). No clinical factors significantly correlated with treatment success.Conclusions: There was an almost seven-fold increase in the mean Tg level 4 d after HIFU ablation. The % of Tg rise in the first week did not appear to correlate with the 6-month nodule shrinkage or treatment success.

The Tumor Associated Lectin Galectin‐3 Can Bind and Sequester Cancer Biomarkers

Most covalently‐linked glycans of glycoprotein cancer biomarkers are potential binding epitopes of tumor‐associated endogenous lectin galectin‐3 (Gal‐3). As glycoprotein biomarkers and Gal‐3 could be secreted by the same tumor cells, they could exist in the same vicinity. We hypothesized that Gal‐3 and the respective biomarker could engage in high affinity binding due to their close proximity. Such binding could result in mutual sequestration through cross‐linked complex formation. We tested our hypothesis by using Thyroglobulin (Tg) and human Gal‐3. Tg, a thyroidal glycoprotein, is a pre‐ and postoperative biomarker of differentiated thyroid cancer (DTC) and Gal‐3 is secreted by malignant thyroid cells. We found that these two biomarkers, produced by thyroid cancer cells, interacted with each other with submicromolar affinity and formed insoluble cross‐linked complexes at their stoichiometric concentrations. One Tg molecule bound up to 14 molecules of Gal‐3. Such complex formation mutually locked both Tg and Gal‐3 in cross‐linked complexes, decreasing the concentration of their freely available forms in the solutions. Formation of the Tg–Gal‐3 complexes was reversible as preformed complexes were found to be sensitive to free Tg and free Gal‐3. Both free Tg and Gal‐3 individually dissolved preformed Tg–Gal‐3 complexes in a concentration‐dependent manner. Complex formation between Tg and Gal‐3 and the sensitivity of the complexes to free Tg and Gal‐3 can potentially influence their biological functions. Sequestration of Tg by Gal‐3 in cross‐linked complexes might also interfere with their clinical detection, the same way Tg autoantibody (TgAb) is reported to interfere in clinical Tg assays. The data presented here also support a model of Gal‐3‐mediated homeostasis of Tg. The present findings could be relevant to other cancers that produce glycoprotein biomarkers and Gal‐3 [1].Support or Funding InformationMichigan Technological University

Clinical impact of thyroglobulin (Tg) and Tg autoantibody (TgAb) measurements in needle washouts of neck lymph node biopsies in the management of patients with papillary thyroid carcinoma.

The presence of thyroglobulin (Tg) in needle washouts of fine needle aspiration biopsy (Tg-FNAB) in neck lymph nodes (LNs) suspected of metastasis has become a cornerstone in the follow-up of patients with papillary thyroid carcinoma (PTC). However, there are limited data regarding the measurement of anti-Tg antibodies in these washouts (TgAb-FNAB), and it is not clear whether these antibodies interfere with the assessment of Tg-FNAB or whether there are other factors that would more consistently justify the finding of low Tg-FNAB in metastatic LNs. We investigated 232 FNAB samples obtained from suspicious neck LNs of 144 PTC patients. These samples were divided according to the patient's serum TgAb status: sTgAb- (n = 203 samples) and sTgAb+ (n = 29). The TgAb-FNAB levels were measured using two different assays. Tg-FNAB was also measured using two assays when low levels (< 10 ng/mL) were identified in the first assay of the metastatic LNs from the sTgAb+ samples. The TgAb-FNAB results were negative in both assays in all samples. Low levels of Tg-FNAB were identified in 11/16 of the metastatic LNs of the sTgAb+ patients and 16/63 of the sTgAb- patients (p < 0.05) using assay 1. The measurement of the Tg-FNAB levels using assay 2 indicated additional metastases in 5 LNs of the sTgAb+ patients. Factors other than the presence of TgAb-FNAB may contribute to the higher number of metastatic LNs with undetectable Tg-FNAB in the sTgAb+ group. In addition, the measurement of Tg-FNAB using different assays was useful to enhance the diagnosis of metastatic LNs, particularly when cytological and Tg-FNAB results are discordant.

Serum Thyroglobulin Concentration Is a Weak Marker of Iodine Status in a Pregnant Population with Iodine Deficiency

Objective: To assess the reliability of thyroglobulin (Tg) as a marker of iodine status during pregnancy. Design: 299 women aged 30.5 ± 4.8 years (mean ± SD) were studied. Methods: In every subject, we measured urinary iodine concentration (UIC), serum thyrotropin (TSH), Tg, free thyroxine (fT₄), Tg autoantibodies (TgAbs) and human chorionic gonadotropin (hCG) levels. We excluded samples with increased TgAbs from the analysis. Results: According to WHO criteria, the study population was iodine deficient in every trimester. Serum Tg levels did not differ during the three trimesters of pregnancy. Serum hCG levels fell significantly as pregnancies advanced. A weak, significantly negative correlation (limited to the 3rd trimester) was found between Tg and UIC (ρ = -0.187, p = 0.039). Serum fT₄ decreased as pregnancies advanced and TSH increased. Serum fT₄ was negatively correlated with TSH (ρ = -0.161, p = 0.006) and positively with hCG (ρ = +0.165, p = 0.005). The multiple regression equation of Tg based on hCG, TSH, UIC and trimester of pregnancy was significant but weak (F = 4.057, p = 0.003; R² = 0.055), with hCG as a significant predictor Tg (p for log hCG = 0.041). Conclusions: Tg cannot be considered as a valid marker of iodine deficiency in pregnancy, at least in a mildly iodine-deficient environment. Further studies in a larger patient cohort with differences in iodine status, as well as studies on Tg changes after improving iodine status in pregnant women, are needed in order to corroborate these results.

Does autoimmunity against thyroglobulin play a role in the pathogenesis of Graves' ophthalmopathy: a review.

While most authors believe that autoimmunity against the TSH receptor expressed in the orbital connective tissue cells is the main reaction that leads to the development of ophthalmopathy in patients with Graves’ hyperthyroidism, an older hypothesis that deserves fresh consideration is based on the notion that thyroglobulin (Tg) in the thyroid gland passes in a retrograde fashion to the orbit where it is recognized by Tg autoantibodies, leading to inflammation. Here, we review new evidence that supports a role of Tg and propose a new hypothesis based on the notion that Tg is targeted in the orbit leading to a complex cascade of reactions that leads to Graves’ ophthalmopathy.