Thyroglobulin autoantibodies of patients with subacute thyroiditis are restricted to a major B cell epitope

COVID-induced thyroid autoimmunity

Breakdown of self-tolerance to thyroid antigens (thyroperoxidase, thyroglobulin and the thyrotropin-receptor) is the driver of thyroid autoimmunity. It has been suggested that infectious disease might trigger autoimmune thyroid disease (AITD). Involvement of the thyroid has been reported during severe acute respiratory syndrome virus 2 (SARS-CoV-2) infection, in the form of subacute thyroiditis in subjects with mild coronavirus disease 19 disease (COVID-19) and of painless, destructive thyroiditis in hospitalized patients with severe infection. In addition, cases of AITD, both Graves' disease (GD) and Hashimoto's thyroiditis (HT), have been reported in association with (SARS-CoV-2) infection. In this review, we focus on the relationship between SARS-CoV-2 infection and occurrence of AITD. Nine cases of GD strictly related to SARS-CoV-2 infection and only three cases of HT associated to COVID-19 infection have been reported. No study has demonstrated a role of AITD as a risk factor for a poor prognosis of COVID-19 infection.

Case report: subacute thyroiditis after receiving SARS-CoV-2 vaccine, maybe not only adjuvants

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) induced the new coronavirus disease 2019 (COVID-19) pandemic worldwide. SARS-CoV-2 vaccines are designed to control the transmission of the disease. However, post-vaccination subacute thyroiditis (SAT) also appears with increase vaccination rate. Three cases of SAT after SARS-CoV-2 vaccines are described in this study. We have reported the patients’ clinical symptoms, laboratory tests, and thyroid imaging. Tests for COVID-19 were all negative, and the patients did not report thyroid-related diseases, autoimmune diseases, or preceding upper respiratory system infections in their medical history. Three female patients showed neck pain on physical examination. The laboratory test results and imaging findings were consistent with the diagnostic criteria of SAT. The patients were carried out a standardized treatment according to their symptoms, and we closely followed up their response to the treatment. Clinicians must be aware of the possibility of SAT after receiving the vaccines and make timely therapy.

Subacute Thyroiditis During the SARS-CoV-2 Pandemic

Context

Acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been related to subacute thyroiditis (SAT).

Objective

We compared SAT cases during the SARS-CoV-2 pandemic to those observed in the previous years.

Methods

A cross-sectional, retrospective study was conducted at the Endocrinology Unit of University Hospital of Pisa, Italy. We included all patients observed from January 2016 to December 2020 because of an untreated SAT, who had developed the disease within 15 days prior to the visit. SAT cases from 2016 to 2019 (N = 152) are referred to as pre-SARS-CoV-2, while 2020 SAT patients are classified as pos-SARS-CoV-2 (N = 18) or neg-SARS-CoV-2 (N = 28), according to positive or negative SARS-CoV-2 testing performed up to 45 days from SAT onset.

Results

While during 2016-2019, most SAT cases were observed in the third quarter, in 2020, 2 peaks were seen, superimposable to the SARS-CoV-2 outbreaks in the second and the fourth quarters. In the second and fourth quarters of 2020, we observed higher levels of free thyroxine (FT4), C-reactive protein (CRP), and thyroglobulin (Tg) compared with the same quarters of the years 2016-2019. Pos-SARS-CoV-2 patients had higher FT4 (28.4 vs 24.1 nmol/L), CRP (8.5 vs 3.6 mg/L), and Tg (155 vs 60 µg/L) (P < 0.05 for all) and more frequently had hypothyroidism (13/15 vs 30/152 at 3 months) (P < 0.001) than pre-SARS-CoV-2 patients. Neg-SARS-CoV-2 patients showed a clinical picture intermediate between the other 2 groups.

Conclusion

The SARS-CoV-2 pandemic has caused a shift in the annual timing and severity of SAT cases.

Subacute Thyroiditis in COVID-19 Patients

OBJECTIVE

As a result of the COVID-19 pandemic that occurred in the last year, it has been revealed that severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) does not only cause viral respiratory tract infection but can also affect many organs in the short or long term. In our study, we aimed to reveal that COVID-19 infection affects the endocrine system and triggers subacute thyroiditis (SAT) in the acute period.

MATERIAL AND METHOD

In our retrospective study, the ear-nose-throat examination, internal diseases consultation (investigation of COVID-19 symptoms and polymerase chain reaction [PCR] test), routine blood tests, T3, T4, thyroid-stimulating hormone, antithyroglobulin (anti-TG), antithyroid peroxidase (anti-TPO), thyroid scintigraphy, and thyroid ultrasonography results of 5 patients who applied to the otorhinolaryngology clinic due to complaints of neck pain and odynophagia between April 2020 and February 2021 were examined.

FINDINGS

All 5 patients were female patients (30.4 years) with odynophagia and pain in the front lower region of the neck. These patients had no previous history of thyroiditis. COVID-19 PCR tests of the patients diagnosed with SAT were positive, and there were no typical COVID-19 signs and symptoms except odynophagia and neck pain.

RESULT

It comes in view that SARS-COV-2 affects thyroid functions and causes SAT and the main symptoms in patients are pain in the neck and odynophagia.

Is Subacute Thyroiditis an Underestimated Manifestation of SARS-CoV-2 Infection? Insights From a Case Series

CONTEXT

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected more than 18 million people worldwide and the pandemic is still spreading. After the first case we reported, we observed 4 additional cases of subacute thyroiditis (SAT) related to SARS-CoV-2 infection.

OBJECTIVES

The objective of this work is to describe additional cases of SAT associated with SARS-CoV-2 infection to alert physicians that SAT may be a manifestation of SARS-CoV-2 infection.

METHODS

We describe clinical, biochemical, and imaging features of 4 patients with SAT related to SARS-CoV-2 infection.

RESULTS

All patients were female (age, 29-46 years). SAT developed 16 to 36 days after the resolution of coronavirus disease 2019 (COVID-19). Neck pain radiated to the jaw and palpitations were the main presenting symptoms and were associated with fever and asthenia. One patient was hospitalized because of atrial fibrillation. Thyroid function tests (available for 3 individuals) were suggestive of destructive thyroiditis, and inflammatory markers were high. At neck ultrasound the thyroid was enlarged, with diffuse and bilateral hypoechoic areas and (in 3 patients) absent vascularization at color Doppler. Symptoms disappeared a few days after commencement of treatment (prednisone in 3 patients and ibuprofen in 1). Six weeks after the onset of SAT, all patients were asymptomatic and inflammatory markers had returned to normal range. Two patients were euthyroid, whereas 2 were diagnosed with subclinical hypothyroidism.

CONCLUSIONS

SAT may be an underestimated manifestation of COVID-19. Clinicians should keep in mind the possible occurrence of SAT during and after SARS-CoV-2 infection.

Subacute Thyroiditis After Sars-COV-2 Infection

CONTEXT

Subacute thyroiditis (SAT) is a thyroid disease of viral or postviral origin. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that began in Wuhan, China, has spread rapidly worldwide and Italy has been severely affected by this outbreak.

OBJECTIVES

The objective of this work is to report the first case of SAT related to SARS-CoV-2 infection.

METHODS

We describe the clinical, laboratory, and imaging features of an 18-year-old woman who came to our attention for fever, neck pain radiated to the jaw, and palpitations occurring 15 days after a SARS-CoV-2-positive oropharyngeal swab. Coronavirus disease 2019 (COVID-19) had been mild and the patient had completely recovered in a few days.

RESULTS

At physical examination the patient presented with a slightly increased heart rate and a painful and enlarged thyroid on palpation. At laboratory exams free thyroxine and free triiodothyronine were high, thyrotropin undetectable, and inflammatory markers and white blood cell count elevated. Bilateral and diffuse hypoechoic areas were detected at neck ultrasound. One month earlier, thyroid function and imaging both were normal. We diagnosed SAT and the patient started prednisone. Neck pain and fever recovered within 2 days and the remaining symptoms within 1 week. Thyroid function and inflammatory markers normalized in 40 days.

CONCLUSIONS

We report the first case of SAT after a SARS-CoV-2 infection. We alert clinicians to additional and unreported clinical manifestations associated with COVID-19.

The Detection of Serum IgMs to Thyroglobulin in Subacute Thyroiditis Suggests a Protective Role of IgMs in Thyroid Autoimmunity

CONTEXT

The role of serum immunoglobulin (Ig)Ms in autoimmune thyroid diseases is uncertain.

OBJECTIVE

We looked for IgMs to thyroglobulin (Tg) in patients with subacute thyroiditis (SAT), which is characterized by high serum Tg levels, the possible de novo appearance of IgGs to Tg (TgAb-IgGs), and no autoimmune sequelae.

MAIN OUTCOME MEASURES

TgAb-IgMs and TgAb-IgGs were detected by binding to Tg using the enzyme-linked immunosorbent assay (ELISA). The upper reference limit of TgAb-IgMs and TgAb-IgGs was established in 40 normal subjects. We looked for TgAb-IgMs in 16 patients with SAT, 11 with Hashimoto's thyroiditis (HT), and 8 with Graves' disease (GD) who were all positive for TgAb-IgGs. IgM binding to bovine serum albumin (BSA), keyhole limpet hemocyanin (KLH), and glucagon in ELISA was measured. Inhibition of TgAb-IgMs binding to coated Tg was evaluated by preincubating serum samples or IgG-depleted samples with soluble Tg.

RESULTS

TgAb-IgMs were positive in 10/16 patients with SAT, 2/11 with HT, and 1/8 with GD. TgAb-IgMs were higher in SAT (0.95; 0.42-1.13) (median; 25th-75th percentiles) than in HT (0.47; 0.45-0.51) and GD patients (0.35; 0.33-0.40) (P < .005 for both). IgM binding of SAT sera to BSA, KLH, and glucagon was significantly lower than Tg. Preincubation with soluble Tg reduced the binding of IgMs to coated Tg by 18.2% for serum samples and by 35.0% and 42.1% for 2 IgG-depleted samples. TgAb-IgM levels were inversely, although nonsignificantly, correlated with Tg concentrations.

CONCLUSIONS

Tg leak associated with thyroid injury induces the production of specific TgAb-IgMs, which, in turn, increases the clearance of Tg and might prevent the establishment of a persistent thyroid autoimmune response.

Moderate Frequency of Anti-Thyroglobulin Antibodies in the Early Phase of Subacute Thyroiditis

BACKGROUND

Subacute thyroiditis is generally believed to be induced by viral infection, and little attention has been paid to anti-thyroid antibodies.

OBJECTIVES

Our study aimed to assess the prevalence of anti-thyroid antibodies in patients with subacute thyroiditis.

METHODS

Anti-thyroglobulin (TgAb) and anti-thyroid peroxidase antibodies (TPOAb) were measured with 4 different immunoassay kits currently used in 40 patients in the early phase of subacute thyroiditis.

RESULTS

The proportion of samples positive for TgAb was 52.5 ± 13.7% (mean of 4 kits), which was significantly (p < 0.05) higher than that positive for TPOAb (15.6 ± 6.5%). The prevalence of positive TgAb alone (negative TPOAb) was also significantly higher than that of TPOAb alone (negative TgAb). TgAb titers decreased or disappeared within 4 months to 6 years in 6 patients.

CONCLUSIONS

Patient samples were moderately positive for TgAb initially, but the titer decreased or disappeared afterwards in subacute thyroiditis.

The Risk of Recurrence of Subacute Thyroiditis Is HLA-Dependent

The frequency of recurrence of subacute thyroiditis (SAT) is rather high, reaching 20–30%. The reason for SAT relapse is still unknown. Recently, we have demonstrated the association between SAT and the presence of HLA-B*18:01, DRB1*01, and C*04:01, apart from the previously known HLA-B*35. The aim of the present study was to evaluate the correlation between SAT-associated HLA haplotypes and the risk of SAT recurrence. HLA-A, -B, -C, -DQB1 and -DRB1 were genotyped using a next-generation sequencing method in 49 SAT patients. The patients were divided into the following HLA groups: 1. HLA-B*35 and/or HLA-C*04, but without any other of the analyzed antigens; 2. HLA-DRB1*01, regardless of the co-presence of HLA-B*35 or -C*04:01, but without HLA-B*18:01; 3. HLA-B18 only, without any other antigen; 4. HLA-B*18:01 plus -B*35, regardless of the presence of any other analyzed antigens. The recurrence rate was compared between the groups. The recurrence rate was significantly increased in patients with HLA-B*18:01 plus HLA-B*35. In conclusion, the risk of SAT recurrence was HLA-dependent and the determining factor was the co-presence of HLA-B*18:01 and -B*35. In such high-risk patients, the steroid treatment regimen should be intensified with a slower dose reduction.

Effect of Thyroglobulin Autoantibodies on the Metabolic Clearance of Serum Thyroglobulin

BACKGROUND

In order to establish whether thyroglobulin autoantibodies (TgAb) influence the metabolic clearance of thyroglobulin (Tg) in humans, serum Tg and TgAb were correlated shortly after radioiodine (¹³¹I) treatment.

METHODS

Samples were collected from 30 consecutive patients undergoing ¹³¹I activity for Graves' hyperthyroidism at the time of treatment and every 15 days thereafter, up to 90 days. Tg and TgAb were measured by immunometric assays (functional sensitivities: 0.1 ng/mL and 8 IU/mL).

RESULTS

Tg was detectable in all patients at day 0. Tg concentrations rose from a mean of 33.2 ng/mL [confidence interval (CI) 17.8-61.0 ng/mL] at day 0 to a mean of 214.6 ng/mL [CI 116.9-393.4 ng/mL] at day 30 and then steadily decreased, reaching the lowest concentration at day 90 (M = 10.9 ng/mL [CI 5.5-20.9 ng/mL]). Compared to their levels at day 0 (M = 23.6 IU/mL [CI 10.5-52.9 IU/mL]), TgAb remained stable through day 15 and then gradually increased up to a mean of 116.6 IU/mL [CI 51.9-262.2 IU/mL] at day 90. Patients were then split into two groups according to their TgAb status at day 0: undetectable (<8 IU/mL; 9 patients) or detectable (≥8 IU/mL; 21 patients) TgAb. Compared to the other cohort, patients with detectable TgAb showed significantly lower Tg concentrations at day 0 (M = 20.3 ng/mL [CI 10.1-40.2 ng/mL] vs. M = 101.8 ng/mL [CI 36.6-279.8 ng/mL]), similar at day 15, lower levels at day 30 (M = 146.5 ng/mL [CI 74.3-287.8 ng/mL] vs. M = 514.8 ng/mL [CI 187.8-1407.9 ng/mL]), at day 45 (M = 87.5 ng/mL [CI 43.1-176.6 ng/mL] vs. M = 337.9 ng/mL [CI 120.1-947.0 ng/mL]), at day 60 (M = 61.6 ng/mL [CI 31.0-121.4 ng/mL] vs. M = 255.8 ng/mL [CI 79.0-823.8 ng/mL]), and at day 75 (M = 24.5 ng/mL [CI 11.9-49.2 ng/mL] vs. M = 249.5 ng/mL [CI 63.5-971.1 ng/mL]), and similar levels at day 90. Patients with detectable TgAb showed a lower (M = 182.5 ng/mL [CI 92.0-361.0 ng/mL] vs. M = 514.8 ng/mL [CI 187.8-1407.9 ng/mL]) and an earlier (day 15 vs. day 30) peak of Tg. The mean Tg concentration was lower in patients with detectable TgAb than in those with undetectable TgAb (area under the curve: 17,340 ± 16,481 ng/mL vs. 36,883 ± 44,625 ng/mL; p = 0.02).

CONCLUSIONS

TgAb influence the changes in Tg concentrations observed immediately after ¹³¹I treatment, inducing lower levels and an earlier peak of Tg. These observations indicate that TgAb significantly influence the metabolic clearance of Tg, supporting the concept that their interference in the measurement of Tg is mainly due to an in vivo effect.

Thyroid Autoantibodies Display both "Original Antigenic Sin" and Epitope Spreading

Evidence for original antigenic sin in spontaneous thyroid autoimmunity is revealed by autoantibody interactions with immunodominant regions on thyroid autoantigens, thyroglobulin (Tg), thyroid peroxidase (TPO), and the thyrotropin receptor (TSHR) A-subunit. In contrast, antibodies induced by immunization of rabbits or mice recognize diverse epitopes. Recognition of immunodominant regions persists despite fluctuations in autoantibody levels following treatment or over time. The enhancement of spontaneously arising pathogenic TSHR antibodies in transgenic human thyrotropin receptor/NOD.H2^h4 mice by injecting a non-pathogenic form of TSHR A-subunit protein also provides evidence for original antigenic sin. From other studies, antigen presentation by B cells, not dendritic cells, is likely responsible for original antigenic sin. Recognition of restricted epitopes on the large glycosylated thyroid autoantigens (60-kDa A-subunit, 100-kDa TPO, and 600-kDa Tg) facilitates exploring the amino acid locations in the immunodominant regions. Epitope spreading has also been revealed by autoantibodies in thyroid autoimmunity. In humans, and in mice that spontaneously develop autoimmunity to all three thyroid autoantigens, autoantibodies develop first to Tg and later to TPO and the TSHR A-subunit. The pattern of intermolecular epitope spreading is related in part to the thyroidal content of Tg, TPO and TSHR A-subunit and to the molecular sizes of these proteins. Importantly, the epitope spreading pattern provides a rationale for future antigen-specific manipulation to block the development of all thyroid autoantibodies by inducing tolerance to Tg, first in the autoantigen cascade. Because of its abundance, Tg may be the autoantigen of choice to explore antigen-specific treatment, preventing the development of pathogenic TSHR antibodies.

A comprehensive score to diagnose Hashimoto's thyroiditis: a proposal

The heterogeneity of diagnostic criteria of Hashimoto's thyroiditis leads to overdiagnosis and prevents strong conclusions from being drawn in clinical studies. The aim of this study is to propose a comprehensive scoring system. A case-control study compared a set of presurgical features of patients with lymphocytic infiltration of the thyroid (Hashimoto's thyroiditis) and controls, in order to design a multi-criteria scoring system. Given a dichotomous outcome (lymphocytic infiltration of the thyroid), a set of covariates was analyzed in 180 patients after total thyroidectomy. A different validation cohort of 1,171 patients was reviewed and classified according to the score. Variables associated with the diagnosis of Hashimoto's thyroiditis were first assessed by univariate analysis. Analysis showed that TPOAb (area under the ROC curve (AUC), 0.67; 95 % CI 0.57-0.77) and TgAb (0.63; 95 % CI 0.54-0.74) were univariate predictors of the diagnosis of HT, which is largely recognized. Combined covariates were then tested using stepwise logistic regression analysis. The final regression model included TPOAb, TgAb, and thyroid vascularity (AUC 0.72; 95 % CI 0.62-0.81). A scoring system was developed, which has a sensitivity of 45.5 % and a specificity of 89.0 %, with a cutoff of 1.7. The likelihood of incident hypothyroidism was higher (OR 2.30; p = 0.004) in the positive (≥1.7) score group. A scoring system has a better performance than any single predictor and is able to identify the subgroup of individuals at higher risk to develop subsequent hypothyroidism.

Iodine, thyroid autoimmunity and cancer

This review focuses on two different topics: (a) iodine and autoimmune thyroid disease (AITD) and (b) AITD and papillary thyroid carcinoma (PTC). Iodine intake modifies the expression of thyroid diseases and has been associated with induction of AITD. Thyroglobulin (Tg) is an important target in iodine-induced autoimmune response due to post-translational modifications of iodinated Tg, as suggested in animal models. We have shown that the unmasking of a cryptic epitope on Tg contributes to iodine-induced thyroid autoimmunity in humans. The relationship between AITD and PTC has been suggested in many studies. The presence of two different mechanisms has been hypothesized, one typical of AITD and the other of an immune reaction to PTC. We have shown that in AITD, the pattern of Tg recognition by anti-Tg antibodies (TgAb) is 'restricted' to the immunodominant regions of Tg, while in patients with non-AITD, such as nodular goiter and PTC devoid of thyroid lymphocytic infiltration at histology, TgAb show a less restricted epitopic pattern and bind also to other regions of Tg. Thyroid function may also affect the frequency of PTC, the risk of cancer increasing with serum TSH levels. We have shown that this mechanism, rather than thyroiditis per se, plays a major role in the association of PTC with Hashimoto's thyroiditis, as a consequence of the autoimmune process leading to a progressive increase of serum TSH in these patients.

Thyroglobulin autoantibodies switch to immunoglobulin (Ig)G1 and IgG3 subclasses and preserve their restricted epitope pattern after 131I treatment for Graves' hyperthyroidism: the activity of autoimmune disease influences subclass distribution but not epitope pattern of autoantibodies

The subclass distribution of thyroglobulin autoantibodies (TgAb) is debated, whereas their epitope pattern is restricted. Radioidine ((131)I) treatment for Graves' disease (GD) induces a rise in TgAb levels, but it is unknown whether it modifies subclass distribution and epitope pattern of TgAb as well. We collected sera from GD patients before (131) I treatment and 3 and 6 months thereafter. We measured total TgAb, TgAb light chains and TgAb subclasses by enzyme-linked immunosorbent assay (ELISA) in 25 patients. We characterized the TgAb epitope pattern in 30 patients by inhibiting their binding to (125-) (I) Tg by a pool of four TgAb-Fab (recognizing Tg epitope regions A, B, C and D) and to Tg in ELISA by each TgAb-Fab. Total TgAb immunoglobulin (Ig)G rose significantly (P = 0.024). TgAb κ chains did not change (P = 0.052), whereas TgAb λ chains increased significantly (P = 0.001) and persistently. We observed a significant rise in IgG1 and IgG3 levels after (131)I (P = 0.008 and P = 0.006, respectively), while IgG2 and IgG4 levels did not change. The rise of IgG1 was persistent, that of IgG3 transient. The levels of inhibition of TgAb binding to Tg by the TgAb-Fab pool were comparable. A slight, non-significant reduction of the inhibition by the immune-dominant TgAb-Fab A was observed 3 and 6 months after (131)I. We conclude that (131)I treatment for GD increases the levels of the complement-activating IgG1 and IgG3 subclasses and does not influence significantly the epitope pattern of TgAb. In autoimmune thyroid disease subclass distribution of autoantibodies is dynamic in spite of a stable epitope pattern.