Comparison of some different methods for analysis of thyroid autoantibodies: importance of thyroglobulin autoantibodies

Evaluation of Different Methods for the Detection of Anti- Thyroglobulin Autoantibody: Prevalence of Anti-Thyroglobulin Autoantibody and Anti-Microsomal Autoantibody in Thyroid Cancer Patients

Four anti-thyroglobulin autoantibodies (TgAb) assays were evaluated for their reference interval, method agreement, concordance etc. Prevalence of TgAb and anti-thyroid peroxidase was studied in differentiated thyroid cancer (DTC) and control. Reference intervals for TgAb assays varied from method to method due to varied assay designs. For TgAb correlation coefficients ranged from 0.74 to 0.99 whereas concordance ranged from 81 to 96.1%. Prevalence of thyroid antibodies mainly TgAb was increased in DTC primarily in females. Use of sensitive immunoassays is recommended for thyroid autoantibody measurement. Diagnosis and follow-up are difficult in DTC with coexisting thyroid autoimmunity. Hence, careful monitoring with regular surveillance is suggested.

Correlates of positive thyroid peroxidase antibodies among firefighters: A cross-sectional-study

Context

Exposure to endocrine disrupting chemicals (EDCs) are associated with underactive thyroid glands, and possibly autoimmunity. Firefighters are exposed to EDCs from flame retardants; however, the prevalence and risk factor associations of thyroid antibodies among firefighters are unknown.

Context

We aimed to determine the prevalence of thyroid peroxidase antibodies (TPOAb) and associated sociodemographic and occupational risk factors among firefighters.

Methods

Firefighters attending professional health and safety conferences between November 2018 and January 2020, and with no prior diagnosis of thyroid disease were invited (n = 278) to submit a health survey, blood samples, and complete a thyroid ultrasound. The survey assessed for sociodemographic and occupational characteristics, including a history of familial thyroid disease, smoking, firefighter tenure, and job rank, radiation exposure, and mitigation practices of occupational exposures. Serum thyroid peroxidase antibody (TPOAb) was also assessed.

Results

Approximately 39.9% of firefighters evaluated had a positive TPOAb test. The mean age for those TPOAb positive was lower than those who tested negative (41.4 ± 7.9 vs 43.1 ± 7.9 years, P = 0.07) but this difference was not significant. Firefighters with a family history of thyroid disease had a statistically significant higher prevalence of TPOAb compared with those without a family history (60.0% vs 37.5%, P = 0.02); this association remained significant after adjusting for sociodemographic and occupational factors (odds ratio 2.99; CI, 1.31-6.85).

Conclusion

The prevalence of TPOAb is high among firefighters in our study, and family history is a significant determinant of testing positive for TPOAb. Firefighters may benefit from TPOAb and thyroid stimulating hormone tests, and screening for family history of thyroid disease at baseline employee medical check-ups. This finding suggests the need for further studies.

Antithyroid Peroxidase Antibodies and Histopathological Outcomes in Egyptian Patients Subjected to Total Thyroidectomy for Non-Malignant Nodular Goiter

Objective

The study aimed to assess antithyroid antibodies in patients with benign thyroid masses and the effect of total thyroidectomy on the antibodies titers.

Patients and Methods

This is a retrospective work of 112 cases managed with total thyroidectomy with positive antithyroid peroxidase antibodies (TPO-Ab), anti-thyroglobulin antibodies (Tg-Ab), or both. All patients were euthyroid before surgery. Thyroid function tests and thyroid antibodies levels were measured before and 6 and 12 months after surgery.

Results

Histopathological evaluation revealed Hashimoto thyroiditis (47.3%), colloid nodules (22.3%), and lymphocytic thyroiditis (30.4%). All patients were TPO-Ab positive, while 96 patients (85.7%) were Tg-Ab positive before surgery. There was no considerable change in TPO-Ab and Tg-Ab after surgery (p = 0.817, and p=0.560, respectively). Also, there was no significant difference between the three histopathological diagnoses in the levels of TPO-Ab (p = 0.086) or Tg-Ab (p = 0.673).

Conclusion

Antithyroid antibodies are not valuable markers for diagnosis or prognosis of benign thyroid diseases subjected to total thyroidectomy. We do not recommend their use beyond supporting evidence of the possibility of the autoimmune nature of the illness if other criteria are confirmed.

Dynamic Changes in Antithyroperoxidase and Antithyroglobulin Antibodies Suggest an Increased Risk for Abnormal Thyrotropin Levels

Background: Antithyroperoxidase (TPOAb) and antithyroglobulin (TgAb) antibodies are associated with abnormal thyrotropin (TSH) levels. However, the effect of dynamic changes in TPOAb and TgAb on incident abnormal TSH is unknown. Methods: A total of 2,387 euthyroid participants aged 18 years or older from three rural areas in northern China were enrolled in this cohort study. Questionnaire interviews and laboratory measurements were performed at baseline in 1999 and at follow-up in 2004. Multinomial logistic regression was used to examine the relationship between changes in thyroid antibodies and incident abnormal TSH levels. Results: In this 5 year follow-up study, TPOAb tier gain was significantly associated with an increased risk of subnormal TSH levels (adjusted RR, 1.535; 95% CI: 1.357-1.736) and supranormal TSH levels (adjusted RR, 1.378; 95% CI: 1.196-1.587), and TgAb tier gain was significantly associated with an increased risk of supranormal (adjusted RR, 1.090; 95% CI: 1.007-1.179) TSH levels. Both thyroid antibody-positive seroconversion and persistent positivity were significantly associated with an increased risk of incident abnormal TSH levels. Thyroid antibody positive seroconversion was associated with a higher risk of incident subnormal TSH than incident supranormal TSH, whereas persistent positive thyroid antibody was associated with a higher risk of incident supranormal TSH than incident subnormal TSH. Conclusions: Dynamic thyroid antibody changes may be related to incident abnormal TSH levels. Those with persistent positive thyroid antibody were more likely to have supranormal TSH than subnormal TSH, and those with positive seroconversion were more likely to have subnormal TSH than supranormal TSH. Further studies are needed to confirm this conclusion and to explore this association mediated by TSH receptor antibodies.

Linear α-(1 → 6)-d-glucan from Bifidobacterium bifidum BIM В-733D is low molecular mass biopolymer with unique immunochemical properties

Role of microorganisms in induction of/protection from autoimmune diseases is proven though molecular mechanisms and bacterial/viral/yeast biopolymers responsible for these effects are in the research stage. Autoantobodies (AAbs) to thyroid peroxidase (anti-TPO) and thyroglobulin (anti-Tg) as well as AAbs to transglutaminase 2 (anti-TG2) and antibodies to gliadins (anti-gliadins) are serological markers of autoimmune thyroid disease and celiac disease, respectively, and players in pathogenesis of these autoimmune diseases. In current study, biopolymer of Bifidobacterium bifidum BIM В-733D that interacts selectively with anti-gliadins (Bb-G_{anti-gliadins}) was isolated by affinity chromatography with anti-gliadins, purified by size exclusion chromatography on TSK 40 gel and identified by NMR as linear α-(1 → 6)-d-glucan with molecular mass about 5000 Da. It was proven that compounds Bb-G_{anti-gliadins} and Bb-G_anti-TPO/Bb-G_anti-Tg isolated early from the same strain [Kiseleva, E. P. et al., Benef Microbes.2013, 4, 375 -391] are the same substance designated G_Bb. Its unique immunochemical property is the ability to interact selectively with anti-TPO, anti-Tg, anti-TG2 and anti-gliadins in presence of no less than 10-fold excess of total immunoglobulins of class G (tIgG), as it was proven by ELISA. Synthesis of G_Bb-bovine serum albumin (G_Bb-BSA) conjugate is an example of increasing the reliability and reproducibility of ELISA results by mediated immobilization of a polysaccharide covalently attached to a well-adsorbed protein. Taking into account that there are population of bispecific anti-gliadins (anti-gliadins and anti-TG2 simultaneously) we regard our data as first argument in favor of hypothesis that G_Bb differentiates between human AAbs per se and other human Ig (e.g. antibodies to antigens of infectious agents) due to its binding with a yet unidentified site which is present in the molecules of all AAbs (independently on their specificity) and absent in other human Igs.

Definition of the upper reference limit for thyroglobulin antibodies according to the National Academy of Clinical Biochemistry guidelines: comparison of eleven different automated methods

Purpose

In the last two decades, thyroglobulin autoantibodies (TgAb) measurement has progressively switched from marker of thyroid autoimmunity to test associated with thyroglobulin (Tg) to verify the presence or absence of TgAb interference in the follow-up of patients with differentiated thyroid cancer. Of note, TgAb measurement is cumbersome: despite standardization against the International Reference Preparation MRC 65/93, several studies demonstrated high inter-method variability and wide variation in limits of detection and in reference intervals. Taking into account the above considerations, the main aim of the present study was the determination of TgAb upper reference limit (URL), according to the National Academy of Clinical Biochemistry guidelines, through the comparison of eleven commercial automated immunoassay platforms.

Methods

The sera of 120 healthy males, selected from a population survey in the province of Verona, Italy, were tested for TgAb concentration using eleven IMA applied on as many automated analyzers: AIA-2000 (AIA) and AIA-CL2400 (CL2), Tosoh Bioscience; Architect (ARC), Abbott Diagnostics; Advia Centaur XP (CEN) and Immulite 2000 XPi (IMM), Siemens Healthineers; Cobas 6000 (COB), Roche Diagnostics; Kryptor (KRY), Thermo Fisher Scientific BRAHMS, Liaison XL (LIA), Diasorin; Lumipulse G (LUM), Fujirebio; Maglumi 2000 Plus (MAG), Snibe and Phadia 250 (PHA), Phadia AB, Thermo Fisher Scientific. All assays were performed according to manufacturers’ instructions in six different laboratories in Friuli-Venezia Giulia and Veneto regions of Italy [Lab 1 (AIA), Lab 2 (CL2), Lab 3 (ARC, COB and LUM), Lab 4 (CEN, IMM, KRY and MAG), Lab 5 (LIA) and Lab 6 (PHA)]. Since TgAb values were not normally distributed, the experimental URL (e-URL) was established at 97.5 percentile according to the non-parametric method.

Results

TgAb e-URLs showed a significant inter-method variability. Considering the same method, e-URL was much lower than that suggested by manufacturers (m-URL), except for ARC and MAG. Correlation and linear regression were unsatisfactory. Consequently, the agreement between methods was poor, with significant bias in Bland–Altman plot.

Conclusions

Despite the efforts for harmonization, TgAb methods cannot be used interchangeably. Therefore, additional effort is required to improve analytical performance taking into consideration approved protocols and guidelines. Moreover, TgAb URL should be used with caution in the management of differentiated thyroid carcinoma patients since the presence and/or the degree of TgAb interference in Tg measurement has not yet been well defined.

The association between thyroid autoantibodies in serum and abnormal function and structure of the thyroid

Objectives

To evaluate the association between thyroid autoantibodies and abnormalities in thyroid function and structure, and to investigate any risk factors.

Methods

A cross-sectional survey was undertaken in Chengdu residents ≥18 years with no previous thyroid disease. The study participants provided demographic and clinical data. Thyroid function and serum concentrations of the thyroid autoantibodies antithyroperoxidase antibody (TPOAb) and antithyroglobulin antibody (TgAb) were measured.

Results

A total of 1334 subjects were included in this study. The prevalence of TPOAb and TgAb positivity was significantly higher in female than in male subjects. The prevalence of thyroid autoantibodies in those with subclinical hypothyroidism and clinical hyper- and hypothyroidism was significantly greater than in euthyroid subjects. The concentration of TPOAb and TgAb in subjects with both TPOAb and TgAb was significantly higher than in those who exhibited only one type of thyroid autoantibody. Using multivariate logistic regression analysis, female sex, thyroid volume, thyroid hypo- and heteroechogenicity were found to be risk factors for the presence of autoantibodies.

Conclusions

Thyroid autoantibodies were common in the general population. Women with thyroid enlargement, hypoechogenicity and heteroechogenicity might benefit from routine screening for thyroid autoantibodies and thyroid function.

Isolation and structural identification of glycopolymers of Bifidobacterium bifidum BIM B-733D as putative players in pathogenesis of autoimmune thyroid diseases

Bifidobacterium bifidum 791 (commercially available as B. bifidum BIM B-733D) cell-surface biopolymers (BPs) interact selectively with human serum thyroid peroxidase (TPO) and thyroglobulin (Tg) autoantibodies (anti TPO and anti Tg, respectively). BPanti-TPO and BPanti-Tg were isolated from the soluble fraction of B. bifidum BIM B-733D by affinity chromatography with anti-TPO or anti-Tg, respectively. Homogeneity of affinity eluates (AEanti-TPO and AEanti-Tg) was tested by size exclusion chromatography. For each AE, the elution profiles generated on the basis of absorbance at 280 nm do not conform to ELISA data for functional activity characteristic of BPs. Moreover, high functional activity was detected in chromatographic fractions that had significantly different molecular weights and no absorbance at 280 nm, which suggests a non-protein (carbohydrate) nature of BPanti-TPO and BPanti-Tg. The semi-preparative size exclusion chromatography of AEanti-TPO and AEanti-Tg with detection by refractometer gave 5,000-7,000 Da fractions containing substances that interact selectively with either anti TPO (BPanti-TPO) or anti-Tg (BPanti-Tg) according to ELISA data. Analysis by two-dimensional NMR spectroscopy including a 1H, 13C-heteronuclear single-quantum coherence experiment indicated that both substances are linear α-1,6-glucans. For the first time, an immunological similarity (molecular mimicry) of glycopolymers of B. bifidum BIM B-733D and human thyroid proteins, TPO and Tg, was shown. On the whole, our data point to a possible role of bifidobacteria in the pathogenesis of autoimmune thyroid diseases (ATD). The main requirements for triggering/acceleration or prevention/abrogation of ATD by bifidobacteria through molecular mimicry mechanism are hypothesised to be (1) genetic predisposition to ATD and (2) intestinal epithelium penetration by α-1,6-glucan.

Thyroglobulin antibody (TgAb) methods - Strengths, pitfalls and clinical utility for monitoring TgAb-positive patients with differentiated thyroid cancer

Thyroglobulin autoantibodies (TgAb) are detected at diagnosis or during treatment in approximately 25% of patients with differentiated thyroid cancer (DTC). When present, TgAb interferes with thyroglobulin (Tg) measurement causing falsely low or undetectable Tg immunometric assay (IMA) values that can mask disease. Guidelines mandate that every Tg test have TgAb measured simultaneously and quantitatively by immunoassay and not a recovery test. The propensity and magnitude of TgAb-Tg interference relates to both Tg and TgAb concentrations and the class of Tg method used. Because the TgAb trend reflects changes in thyroid tissue mass, TgAb concentrations serve as a surrogate post-operative DTC tumor marker. A rising, or de novo appearance of TgAb may indicate recurrence, whereas a progressive decline suggests successful treatment. This review focuses on the technical limitations of current TgAb methods, characteristics of TgAb interference with different classes of Tg method, and the clinical value of monitoring TgAb trends as a surrogate DTC tumor marker.

Decreased CD4+CD152+ T cell subset and its correlation with the level of antithyroid antibodies in children with chronic autoimmune thyroiditis

Objective

Cytotoxic T lymphocyte antigen-4 (CTLA-4) is one of the basic antigens involved in immune responses regulation associated with autoimmune thyroid diseases. The aim of the study was to evaluate whether the surface expression of CTLA-4(CD152) on T cells is correlated with laboratory autoimmune markers in children with Hashimoto's disease.

Material and methods

Blood samples were obtained from 45 children with Hashimoto's thyroiditis of the mean age 14.8 ± 2.35 years, and from 55 healthy age-matched children, free of allergic, immune and hematological disorders, and with a normal thyroid function. The anti-thyroid antibodies were measured with Microparticle Enzyme Immunoassay (AxSYM Anti-Tg, AxSYM Anti-TPO). The T cell phenotype was evaluated flow cytometery, with the use of monoclonal antibodies combination: CD4- FITC/CD28 -PC5/CD152 -PE and CD8 -FITC/CD28 -PC5/CD152 -PE

Results

The percentage of T cells with CD152 expression was significantly decreased in children with Hashimoto's thyroiditis compared with healthy controls (P < 0.001). A significant negative correlation was found between the level of anti-thyroglobulin antibodies and the percentage of CD4+CD152+ T cells (r = -0.34; P < 0.05). Anti-thyroperoxidase antibodies did not correlate with CD152 expression.

Conclusions

In children with Hashimoto's thyroiditis, the number of CD4+CD152+ T cells is decreased and negatively correlates with the level of anti-thyroglobulin antibodies.

Autoimmune thyroid diseases in a large group of Hungarian patients with primary Sjögren's syndrome

BACKGROUND

Previous studies on relatively small populations of patients with primary Sjögren's syndrome (pSS) suggested an association between pSS and Hashimoto's thyroiditis (HT). As some findings in the literature regarding the relationship between pSS and thyroid disease are contradictory, and there is little information on the sequence of pSS and HT, we conducted a study with a population of patients with pSS that was about three times larger than previously studied populations. Our objective was to determine the prevalence of HT and Graves' disease (GD) in patients with pSS and to assess the sequence of pSS and autoimmune thyroid diseases.

METHODS

A total of 479 patients with pSS were retrospectively studied. Thyroid ultrasound and scintigraphy were performed, and serum thyrotropin, free triiodothyronine, free thyroxine, antithyroid peroxidase antibody (TPOAb), and anti-thyroglobulin autoantibody (TgAb) measurements were carried out. Solitary thyroid nodules were investigated by fine-needle aspiration biopsy.

RESULTS

Thyroid dysfunction was found in 95 patients (21.25%). Thirty of these patients had HT and 18 had GD. HT predated pSS in eight patients, developed at approximately the same time in seven patients, and followed pSS in 15 patients. Almost all (90%) patients with HT had persistently elevated serum TgAb or TPOAb titers.

CONCLUSIONS

An association between HT and pSS was found based on the fact that the frequency of HT was greater among pSS patients (6.26%) than in the general population (1-2%). In contrast, no association between GD and pSS was found. We noted that both HT and GD can appear either before or after the onset of pSS. Since most cases of pSS predate the appearance of autoimmune thyroid diseases it is important to determine if pSS is a predisposing factor for the development of autoimmune thyroiditis.

Antithyroperoxidase and antithyroglobulin antibodies in a five-year follow-up survey of populations with different iodine intakes

OBJECTIVE

In a follow-up study, we determined the prevalence, incidence, and natural course of positive antithyroperoxidase antibodies (TPOAbs) and antithyroglobulin antibodies (TgAbs) in the general population and examined the influences of iodine intake.

DESIGN

The study was conducted in Panshan, Zhangwu, and Huanghua, regions with mildly deficient, more than adequate, and excessive iodine intake, respectively. Of the 3761 unselected subjects who were enrolled at baseline, 3018 participated in the 5-yr follow-up study. Serum TSH, TPOAb, and TgAb levels were measured.

RESULTS

Among subjects in Panshan, Zhangwu, and Huanghua, the prevalence of positive TPOAbs was 11.23, 11.83 and 12.02%, respectively, whereas 11.23, 11.17, and 11.26% of subjects were TgAb positive, respectively. In the older population (> or =45 yr), TgAb-positive individuals were more frequent in Huanghua than Panshan and Zhangwu (P < 0.05). The 5-yr cumulative incidence of positive TPOAb was 2.08, 3.84, and 2.84% in Panshan, Zhangwu, and Huanghua, respectively, whereas 2.91, 3.64, and 5.07% of subjects were TgAb positive, respectively (P < 0.05), corresponding to the increase in iodine intake. Subjects who were TPOAb and/or TgAb positive at baseline developed thyroid dysfunctions more frequently than those without antibodies (14.44 vs. 3.31%, P < 0.01); their incidence of elevated TSH levels was 1.32, 8.46, and 15.38% in Panshan, Zhangwu, and Huanghua, respectively (P < 0.05).

CONCLUSIONS

Subjects who were TPOAb and TgAb positive at baseline developed thyroid dysfunctions more frequently than seronegative subjects. High iodine intake was a risk factor for developing hypothyroidism in antibody-positive subjects. A constant exposure to excessive iodine intake increased the incidence of positive TgAb.

The role of autoimmunity at diagnosis of type 1 diabetes in the development of thyroid and celiac disease and microvascular complications

OBJECTIVE

The purpose of this study was to explore whether the presence of thyroid and endomysial autoantibodies at diagnosis of type 1 diabetes in children predicts development of thyroid and celiac disease, respectively, and whether diabetes-associated autoantibodies at diagnosis predict development of microvascular complications up to 13 years later.

RESEARCH DESIGN AND METHODS

Autoantibodies were measured at diagnosis of type 1 diabetes in 173 children aged 0-15 years and included thyroperoxidase antibody (TPOA), endomysial antibody (EMA), islet cell autoantibody, GAD antibody (GADA), and insulin autoantibody. Thyroid disease was defined as thyroid stimulating hormone level > or = 5 microU/ml. Celiac disease was confirmed by small-bowel biopsy. Assessment of microvascular complications included stereoscopic fundal photography, pupillometry, thermal threshold, and albumin excretion rate (AER).

RESULTS

The incidence rates for thyroid and celiac disease were 0.9 and 0.7 per 100 patient-years, respectively. Within 13 years, 6 of 13 children with positive TPOA tests at diagnosis developed thyroid disease compared with 5 of 139 children with negative TPOA tests (P < 0.001). All four patients with positive EMA titers at diagnosis had biopsy-proven celiac disease. Five of 11 patients who developed thyroid disease and 4 of 8 who developed celiac disease had negative TPOA and EMA tests at diagnosis, respectively. Retinopathy was detected in 39% and elevated AER in 36%. The presence of diabetes-associated autoantibodies at diagnosis did not predict microvascular complications though GADA titer levels predicted pupillary abnormality.

CONCLUSIONS

Elevated TPOA and EMA levels at diagnosis of type 1 diabetes predict the development of thyroid and celiac disease, respectively. In children with negative antibody titers at diagnosis, screening at 2-year intervals is recommended.

Thyroglobulin as an autoantigen: what can we learn about immunopathogenicity from the correlation of antigenic properties with protein structure?

Autoantibodies against human thyroglobulin are a hallmark of autoimmune thyroid disease in humans, and are often found in normal subjects. Their pathogenic significance is debated. Several B-cell epitope-bearing peptides have been identified in thyroglobulin. They are generally located away from the cysteine-rich regions of tandem sequence repetition. It is possible that our current epitopic map is incomplete because of the difficulty that proteolytic and recombinant approaches have in restituting conformational epitopes based upon proper pairing between numerous cysteinyl residues. Furthermore, the homology of cysteine-rich repeats with a motif occurring in several proteins, endowed with antiprotease activity, suggests that these regions may normally escape processing and presentation to the immune system, and brings attention to the mechanisms, such as oxidative cleavage, by which such cryptic epitopes may be exposed. A number of T-cell epitope-bearing peptides, endowed with thyroiditogenic power in susceptible mice, were also identified. None of them was dominant, as none was able to prime in vivo lymph node cells that would proliferate or transfer autoimmune thyroiditis to syngeneic hosts, upon stimulation with intact thyroglobulin in vitro. More than half of them are located within the acetylcholinesterase-homologous domain of thyroglobulin, and overlap B-cell epitopes associated with autoimmune thyroid disease, while the others are located within cysteine-rich repeats. The immunopathogenic, non-dominant character of these epitopes also favours the view that the development of autoimmune thyroid disease may involve the unmasking of cryptic epitopes, whose exposure may cause the breaking of peripheral tolerance to thyroglobulin. Further research in this direction seems warranted.

Increased sensitivity of a new assay for anti-thyroglobulin antibody detection in patients with autoimmune thyroid disease

OBJECTIVES

To verify the cut-off values and to determine the clinical sensitivity of antithyroglobulin (TgAb) determinations using our routine RIA and the new electrochemiluminescent Elecsys assay.

DESIGN AND METHODS

We used the DYNOtest anti-Tgn manual RIA from BRAHMS and the new automated Elecsys electrochemiluminescent immunoassay from Roche Diagnostics. We analyzed 452 sera from the following subjects: 193 euthyroid controls, 163 with treated and untreated autoimmune thyroid diseases (AITD) (108 Graves' disease and 55 thyroiditis), 50 with differentiated thyroid carcinoma, 13 with nonautoimmune thyroid disease and 33 with type 1 diabetes mellitus.

RESULTS

As expected, using the proposed thresholds (BRAHMS 60 kIU/L, Elecsys 115 kIU/L) approximately 6% of the control subjects were positive for TgAb with both methods. In AITD patients, the sensitivity of TgAb determination was significantly higher with the Elecsys assay (51.5%) than with the BRAHMS assay (39.3%). This difference was not observed in the other patient groups.

CONCLUSION

The Elecsys assay can be preferred not only because it is automated and rapid, but also because of its better clinical performance in AITD patients.

Thyroid peroxidase and thyroglobulin autoantibodies in a large survey of populations with mild and moderate iodine deficiency

BACKGROUND AND AIMS

Autoimmune thyroiditis is one of the most common autoimmune disorders. Autoantibodies against the thyroid gland, with thyroid peroxidase antibody (TPO-Ab) and thyroglobulin antibody (Tg-Ab) as the most common autoantibodies, can often be demonstrated in serum in population surveys. In the present study we evaluated if TPO-Ab and Tg-Ab tend to develop in parallel or whether one or the other may be more prevalent in subsets of the population.

METHODS

In a cross-sectional comparative study, performed in two areas of Denmark with mild and moderate iodine deficiency, 4649 randomly selected subjects in age groups between 18 and 65 years were examined. Blood tests were analysed for TPO-Ab and Tg-Ab using assays based on the radioimmunoassay (RIA) technique. The participants answered questionnaires, were clinically examined and had urine samples collected.

RESULTS

The overall prevalence rate of thyroid autoantibodies (TPO-Ab and/or Tg-Ab) was 18.8%. The prevalence rates of TPO-Ab and Tg-Ab were similar (13.1 vs. 13.0%). Both antibodies were more frequent in females than in males, and in females the prevalence rates increased with age. In the age group 60-65 years thyroid antibodies were more frequently measured in sera from moderate than from mild iodine-deficient area (P = 0.02), whereas no differences were seen in younger subjects. In 38.8% of participants with thyroid autoantibodies in serum, both antibodies were present. In sera with both TPO-Ab and Tg-Ab present the concentrations of the antibodies were generally higher than in sera with only one type of antibody present.

CONCLUSION

The prevalence rates of TPO-Ab and Tg-Ab were similar in this large population survey. The results suggest that TPO-Ab and Tg-Ab predominantly develop due to a general alteration in the immune system, whereas specific antigenic mechanisms are probably of less importance. However, further studies are needed to clarify the mechanisms involved in the development of thyroid autoantibodies.

Thyroid autoimmunity in chronic idiopathic urticaria: implications for therapy

The association between thyroid autoimmunity and chronic idiopathic urticaria has long been recognized, although prevalence rates differ in the studies reported to date (from 12 to 29%). There is, therefore, a strong indication to screen patients affected by chronic urticaria of unknown origin for thyroid antibodies (antithyroperoxidase and antithyroglobulin) and, when positive, for serum thyrotropin to assess thyroid functional status. Less clear is the implication of thyroid autoimmunity for therapy, as most patients with urticaria who have associated thyroid autoimmunity are euthyroid. There is no doubt that cases with clinical or subclinical thyroid dysfunction should undergo treatment with either levothyroxine or antithyroid drugs for hypo- or hyper-function, respectively. Although the best remission rates for symptoms of urticaria have so far been obtained with levothyroxine in patients who are euthyroid, monitoring of thyroid function through serum thyrotropin determination is highly recommended because of the risk of hyperthyroidism, especially in the elderly.