Studies on thyroid cell surface antigens using cultured human thyroid cells.

Human thyroid cells in primary culture were used for studies of thyroid cell surface antibodies in patients with thyroid autoimmune disorders. Radioiodinated IgG preparations containing thyroid microsomal antibody (TMAb), thyroid stimulating antibody (TSAb) and/or thyroglobulin antibody (TgAb) were tested for binding to thyroid cells. Binding was observed with radioiodinated IgG from patients with Graves' disease, Hashimoto's thyroiditis and idiopathic myxoedema containing TMAb, irrespective of the presence of TSAb and TgAb, while negative results were obtained with normal IgG. A dose-dependent inhibition of binding to thyroid cells was produced by the addition of the corresponding unlabelled IgG preparations. Evidence for tissue specificity was provided by the absence of binding to human skin fibroblasts used as controls. Preabsorption with human thyroid microsomes completely abolished the binding to thyroid cells of a radioiodinated TMAb positive IgG preparation, while only incomplete removal of the reactivity to thyroid microsomes was produced by preabsorption with thyroid cells. These data suggest that some but not all microsomal antigenic determinants are expressed on the thyroid cell surface. Binding to thyroid cells was also observed with purified TgAb, indicating that thyroglobulin antigenic determinants are present on the surface of thyroid cells. No evidence of binding was obtained with a TSAb positive Graves' IgG preparation with undetectable TMAb and TgAb. Unlabelled IgG preparations containing TMAb from patients with either Hashimoto's thyroiditis or idiopathic myxoedema were shown to inhibit the binding to thyroid cells of radioiodinated TMAb positive Graves' IgG and vice versa. These data indicate that antibodies present in these thyroid autoimmune disorders share common thyroid cell surface antigens. However, the binding of radioiodinated IgG from a patient with idiopathic myxoedema was only partially inhibited by Graves' or Hashimoto's IgG, suggesting that some of the thyroid cell surface antibodies of idiopathic myxoedema may not be detectable in other thyroid autoimmune disorders.     

Significance of anti-eye muscle antibody in patients with thyroid-associated ophthalmopathy by quantitative western blot.

To investigate the prevalence of antibody against rat eye muscle membrane antigen, as determined from SDS-polyacrylamide gel electrophoresis and western blotting, in sera from patients with thyroid-associated ophthalmopathy (TAO), we quantitatively analyzed the binding activity with a rat eye muscle membrane 64 kDa protein using chromato-scanner. Eye muscle antibody activity was expressed as ratio of density of the 64 kDa band to that at 66 kDa found with all normal sera and phosphate buffered saline. The mean (+/- SD) eye muscle antibody activity was 2.7 +/- 2.7 in TAO (P < 0.01 v.s. normal), 1.5 +/- 1.7 in Graves' disease without evident eye disease, 1.6 +/- 2.5 in Hashimoto's thyroiditis and 0.45 +/- 0.26 in normal subjects. A positive band at 64 kDa was found in 71% of patients with TAO, 36% of those of Graves' disease without evident eye disease and in 35% of patients with Hashimoto's thyroiditis without eye disease. The prevalence of this antibody activity tended to correlate to the severity of ophthalmopathy. Furthermore, the level of eye muscle antibody activity decreased in parallel with the improvement of eye signs in two patients. Sera reactive with rat eye muscle membrane 64 kDa protein reacted also with a human eye muscle membrane 64 kDa protein but not with human thyroid, liver, spleen or pancreas membrane preparations. In conclusion, antibody to rat eye muscle membrane 64 kDa protein is present in TAO and may be a useful clinical marker of ophthalmopathy.     

Ultrastructural localization of endogenous peroxidase activity in Hashimoto's thyroiditis

Ultrastructural localization and intensity of endogenous thyroid peroxidase (TPO) in Hashimoto's thyroiditis were examined in relation to the serum thyroid hormone level, thyroid-stimulating hormone (TSH) concentration and anti-thyroid autoantibody titer. In Hashimoto's thyroiditis, TPO activity on the microvilli of follicular cells was more intense than that of normal thyroid tissue, but the intensity of the intracytoplasmic peroxidase reaction was generally weaker than that of Graves' or normal thyroid tissue. Microvillar TPO reaction products were positive in all thyroid follicular cells in patients with increased TSH levels, but no TPO activity was observed on the microvilli of patients with normal or low TSH levels, irrespective of their histological type or serum anti-microsomal antibody titer. It is suggested that TPO activity on the surface of microvilli of thyroid follicular cells in Hashimoto's thyroid gland is modulated by thyrotropin but is not affected by anti-thyroid autoantibodies.     

Isotype and immunoglobulin subclass distribution of eye muscle membrane reactive antibodies in the serum of patients with thyroid-associated ophthalmopathy as detected in Western blotting.

We have determined the immunoglobulin (Ig) class (isotype) and IgG subclass of autoantibodies in the serum of patients with thyroid-associated ophthalmopathy (TAO) or autoimmune thyroid disorders without evident ophthalmopathy reactive in Western blotting with antigens of 55, 64, 75 and 95 kDa in pig eye muscle membrane (PEMM). The 22 sera studied were shown, previously, to contain IgG antibodies reactive with one or more of the four antigens. The majority of sera antibodies reactive with PEMM antigens were of two or more IgG subclasses. Of the IgG subclass specificities IgG3 and IgG4 subclass antibodies were, overall, the most common. We were unable to demonstrate IgG subclass restriction for antibodies reactive with the 95 or 55 kDa antigens in PEMM, antibody activity being equally distributed in all four subclasses tested. While most of the sera which recognized a 64 kDa antigen did so with an IgG4 antibody, all other subclasses were also represented. On the other hand all 13 sera reactive with a 75 kDa antigen did so using Ig of the IgG3 subclass and 12 of these used the IgG4 subclass as well, IgG1 and IgG2 subclasses being represented in only 3 and 4 sera, respectively. There were no differences, in respect to Ig class or IgG subclass distribution of eye muscle reactive antibodies between patients with Graves' hyperthyroidism with ophthalmopathy and those with Hashimoto's thyroiditis, and eye disease. Control sera from five normal subjects and three patients with nonautoimmune thyroid disorders did not contain antibodies reactive with these PEMM antigens of any Ig class or IgG subclass.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunoblotting for the detection of TSH receptor autoantibodies.

Immunoblotting was optimized to detect autoantibodies to TSH receptors from human and porcine thyroid tissue and to determine their epitope specificity. Autoantibodies to putative TSH receptor proteins in thyroid particulate membranes were detected in approximately 35% of sera from patients with Graves' disease. However, despite modifications to increase immunoblotting sensitivity and specificity, only a minority (less than 15%) of Graves' disease sera contained autoantibodies that identified epitopes within TSH affinity-purified human or porcine receptor proteins. In these sera there was no correlation between the TSH receptor antibody titre, determined by radioreceptor assay, and receptor epitope reactivity. The sensitivity of immunoblotting was limited by reduced transfer of purified receptor from the gel. However, in addition, the inability to immunoblot the purified receptor with a majority of Graves' sera, under conditions designed to enhance receptor renaturation, appears to reflect a strict conformational requirement for immunoreactivity. Immunoblotting of purified receptors therefore has a limited application in detecting, and defining the epitope reactivity of, TSH receptor autoantibodies.     

Tryptic peptides of human thyroglobulin: II. Immunoreactivity with sera from patients with thyroid diseases.

Tryptic peptides of human thyroglobulin (Tg) were analysed by Western immunoblot for their reactivity to circulating autoantibodies from patients with Hashimoto's thyroiditis (HT), Graves' disease (GD) and thyroid carcinoma, and from normal human controls. Low molecular weight peptides were released after 4 h incubation of Tg with trypsin. The sera of thyroid disease patients reacted with several peptides, but predominantly bound three peptides with apparent molecular weights (MWap) of 25 kD, 20 kD, and 15 kD; the sera of normal individuals did not bind these fragments of Tg. The pattern of tryptic peptides recognized by the majority of sera from GD patients differed from that recognized by sera from most patients with HT. Autoantibodies from both groups of patients recognized a 15-kD peptide with a high frequency, but the sera from 26/43 (60%) GD patients also recognized a peptide with MWap of 25 kD, whereas the sera from 22/35 (63%) of HT patients recognized a 20-kD peptide. A few sera from patients with thyroid carcinoma reacted with peptides with MWap of 15 and 20-kD, and none bound the 25-kD peptide. The immunoreactivity of autoantibodies in HT sera to the 20-kD peptide paralleled the competitive inhibition of the MoAb 137C1 by these sera. In addition, MoAb 137C1 and Hashimoto's sera showed the same Western immunoblot-binding pattern to Tg tryptic peptides, suggesting that a Hashimoto-associated epitope and the 137C1-binding site are found on the same peptide. These findings suggest that distinct peptides are recognized by Tg autoantibodies from patients with different thyroid diseases.     

Assays of TSH-receptor antibodies in 576 patients with various thyroid disorders: their incidence, significance and clinical usefulness

The incidence and the significance of TSH-receptor antibodies in Graves' disease and in various thyroid disorders have been evaluated. TSH-binding inhibiting antibodies (TBIAb) and thyroid stimulating antibodies (TSAb) were detected in a large proportion of Graves' disease patients (TBIAb in 68.8% and TSAb in 77.8%), in a small number of patients with idiopathic myxoedema or Hashimoto's thyroiditis, and were not detected in patients with endemic euthyroid goitre, differentiated thyroid carcinoma and toxic adenoma. Furthermore, TSH-receptor antibodies were present in some patients with toxic multinodular goitre (TBIAb in 12.7% and TSAb in 15.9%). When TSH-receptor and other thyroid autoantibodies were compared, it was found that 13 of the 15 Graves' patients with negative tests for thyroglobulin and thyroid microsomal antibodies were positive for TSH-receptor antibodies. On the other hand, 9 of the 11 patients with toxic multinodular goitre who had positive TSH-receptor antibody tests, also had serum thyroglobulin and/or thyroid microsomal antibodies. No significant differences in the prevalence of TSH-receptor antibodies were found in Graves' patients irrespective of the presence of ophthalmopathy or pretibial myxoedema. Elevated TBIAb activity at the end of anti-thyroid drug treatment was found in 52.9% of Graves' patients who subsequently relapsed, while in Graves' patients in remission TBIAb was always negative. TSH-receptor antibody results were not predictive of the outcome of radioiodine treatment in Graves' disease. Finally no correlation could be found between TBIAb and TSAb in Graves' disease and Hashimoto's thyroiditis. In conclusion: the high incidence of TSH-receptor antibodies in Graves' disease confirms their pathogenetic role in the development of hyperthyroidism; TSH-receptor antibodies in Graves' disease are not significantly associated with the presence of ophthalmopathy or pretibial myxoedema; TSH-receptor antibody assays may be useful for the diagnosis of Graves' disease in the absence of other signs of autoimmunity. TBIAb seems to be a good predictor of relapse in Graves' patients treated with anti-thyroid drugs; a fraction of toxic multinodular goitre could be a nodular variant of Graves' disease.     

Autoantibodies to p53 in sera of patients with autoimmune thyroid disease

Mutations in the tumor suppressor gene, p53, lead to intracellular accumulation of abnormal p53 protein and are associated with p53 autoantibodies. p53 also accumulates in autoimmune diseases and Hashimoto's thyroiditis, but it is unknown if p53 autoantibodies occur in the latter. We measured p53 autoantibodies in the sera of 93 patients with thyroid disease and 19 patients without thyroid disease. Anti-p53 antibodies were detected in the sera from 4.2% (2/48) of patients with autoimmune thyroid disease, including one patient with Hashimoto's thyroiditis (3.7%, 1/27) and one with Graves' disease (4.8%, 1/21). A third patient with pseudohypoparathyroidism, but without thyroid disease, was also positive (1/19; 5.2%). None of 19 patients with differentiated thyroid cancer had anti-p53 antibodies. We conclude that anti-p53 antibodies can be detected in the sera from approximately 4% of patients with autoimmune thyroid disease. This finding suggests that increased DNA damage and apoptosis may be associated with autoimmune thyroid disease.     

Autoantibodies highly increased in patients with thyroid dysfunction

To evaluate the significance of antithyroid antibodie levels, five hundred and twenty-six patients with thyroid diseases and 292 health subjects from Yuci district, Shanxi province, China, were studied. Serum levels were determined for thyroid hormone receptor antibody （TRAb）, microsomal antibody （TMAb） and thyroglobulin antibody （TGAb）. Among patients, the percentages for nodular goiter and thyroid adenoma, Graves＇ disease, and Hashimoto＇s thyroiditis are 44.1%, 19.6% and 17.7%, respectively. The ratios of female to male were 2.0 to 15.6. Antibody-positive patients for TMAb, TGAb and TRAb were detectable as 94.6%, 76.3% and 20.4% for Hashimoto＇s thyroiditis, and 40.0%, 30.0% and 90.3% for Graves＇s disease. In conclusion, the high levels of the TRAb in Graves＇ disease, and those of the TGAbFFMAb in Hashimoto＇s thyroiditis and idiopathic hypothyroidism are meaningful for characterizing the epidemiological basis of the diseases and for using as prognostic indicators for the relapse in individual patients. Cellular ＆ Molecular Immunology.     

Various expressions of a unique anti-human thyroglobulin antibody repertoire in normal state and autoimmune disease

Polyclonal anti-human thyroglobulin (hTgb) antibodies (Ab) were purified from sera of rabbits immunized with human thyroglobulin, normal humans and patients suffering from Graves' disease, Hashimoto's thyroiditis and thyroid carcinoma. The avidity of the various Ab preparations for hTgb ranged from 0.3 X 10(10) -2.2 X 10(10) M-1. By using well characterized mouse monoclonal antibodies (mAb) directed against hTgb, it was shown that the fine specificities of induced anti-hTgb Ab in rabbits, natural Ab in normal subjects and autoantibodies in diseased patients were similar; however, they differed from that of rabbit anti-bovine and anti-porcine thyroglobulin Ab which were able to inhibit the hTgb binding of only a few of the mAb. Anti-hTgb in rabbits and in patients with thyroid carcinoma varied from those in normal subjects only by uniformly elevated serum titers. In contrast, patients with Graves' disease and Hashimoto's thyroiditis showed an increased concentration essentially restricted to Ab reacting with few of the antigenic determinants recognized by the mAb. Our data suggest that the repertoire of anti-hTgb Ab is similar in mouse, rabbit and human. Furthermore, the finding of identical fine specificities for anti-hTgb Ab in normal and pathological conditions implies that autoantibodies are produced in normal subjects and held to a low level by regulatory processes which fail with respect to selected epitopes in autoimmune diseases.     

运用ROC曲线方法评价TRAb、TPO-Ab和TGA在Graves'病和HT鉴别诊断中的意义

目的:应用临床诊断性能(ROC)曲线方法评价TSH受体抗体(TRAb)、甲状腺过氧化物酶抗体(TPO-Ab)和甲状腺球蛋白抗体(TGA)在Graves'病(格雷夫斯病)和桥本甲状腺炎鉴别诊断中的意义.方法:以甲状腺细针穿刺细胞学检查结果作为诊断金标准,以采用化学发光法测定63例自身免疫性甲状腺病患者血清的TRAb、TP...     

In vitro production of interferon-gamma by peripheral blood from patients with Graves'' disease, Hashimoto''s thyroiditis and rheumatoid arthritis.

The production of interferon-gamma (IFN-gamma) by peripheral blood mononuclear cells (PBMC), CD4 cells, or CD8 cells in response to interleukin-2 (IL-2) stimulation has been studied; the samples were obtained from 12 healthy control subjects, 19 patients with Graves' disease (10 hyperthyroid and nine euthyroid), 13 patients with Hashimoto's thyroiditis (four hypothyroid and nine euthyroid), and 15 patients with rheumatoid arthritis (11 active and four inactive). A dose of IL-2 (25 U/ml) was utilized to induce IFN-gamma by PBMC from all four groups. The incremental increase in IFN-gamma values (with IL-2 stimulation minus without stimulation) was significantly less in PBMC from patients with Graves' disease, Hashimoto's thyroiditis, and rheumatoid arthritis than that in PBMC from control subjects. The values from PBMC in patients with Graves' disease in a euthyroid state were below normal but greater than those from patients with Graves' disease in a hyperthyroid state. The incremental increase in IFN-gamma values from Graves' disease PBMC correlated with the serum TSH values (r = 0.622, P less than 0.01), but not with thyroid autoantibodies (anti-thyroid microsomal antibodies, anti-thyroid microsomal antibodies, nor TSH-binding inhibitory immunoglobulin activities). The incremental increase in IFN-gamma from PBMC from both control subjects and Graves' disease was correlated with that from CD4 cells (r = 0.711, P less than 0.01), but not with that from CD8 cells. The production of IFN-gamma in response to IL-2 from PBMC in Graves' disease correlated inversely with thyroid function, appearing to reflect the very effect of hyperthyroidism in this process. The precise explanation of these phenomena remains unclear. The decreased response of IFN-gamma to IL-2 stimulation by PBMC from patients with Graves' disease, Hashimoto's thyroiditis, and rheumatoid arthritis seems to be a non-specific phenomenon occurring in both organ specific autoimmune disease and systemic autoimmune disease. It may be due to a down-regulation in autoimmune disease of CD4 cells in response to IL-2, a decreased level of IL-2 cellular receptors or a decreased receptor affinity, associated increased soluble IL-2 receptors, or a defect of the intra-CD4 cellular IL-2 signal to produce or release IFN-gamma in the conditions studied.     

Structural features of the autoantigens involved in thyroid autoimmune disease: the thyroid microsomal/microvillar antigen

The microsomal/microvillar antigen of the human thyroid gland which provokes thyroid autoimmunity was characterised by immunoprecipitation studies. Sera from patients with Hashimoto's thyroiditis, primary myxoedema or Graves' disease containing autoanti-microsomal antibody specifically precipitated a component, which under reducing conditions migrates with a mol. wt of 105,000 on SDS-polyacrylamide gel electrophoresis. This protein was absent in auto- or xeno-anti-thyroglobulin precipitates, which under reducing conditions display four polypeptides of Mr 260,000, 230,000, 180,000 and 142,000. Under non-reducing conditions, the microsomal/microvillar antigen displayed a small shift in mobility to a mol. wt of 117,000 suggesting the presence of intrachain disulphide bonds. In contrast, under these conditions, anti-thyroglobulin precipitated components displaying polypeptides of approx. mol. wts in the region of 240,000-260,000, 170,000-180,000 and 140,000. Absorption of thyroiditis sera on thyroglobulin-Sepharose followed by immunoprecipitation abolished the anti-thyroglobulin components without affecting the binding of the 105,000-dalton polypeptide, if the sera contained antimicrosomal antibody. No comparable material was identified in microsomal membrane preparations prepared from the stomach which is also commonly involved in organ-specific autoimmunity. The 105,000-dalton component does not bind to a Lens culinaris lectin affinity column. We conclude that the epitopes of the microsomal/microvillar antigen are presented on a poorly glycosylated peptide of mol. wt 105,000, which is probably stabilised by intrachain disulphide bonds and which does not share serological reactivity with membrane-bound thyroglobulin.     

Comparison of radioassay and haemagglutination methods for anti-thyroid microsomal antibodies.

Parallel measurements of circulating anti-thyroid microsomal (anti-M) antibodies by radioassay and haemagglutination were performed on subjects with or without thyroid disorders. Three-quarters (75.4%) of control subjects had undetectable antibody levels (less than 10 u/ml) by radioassay and only 3.1% had concentrations of greater than or equal to 75 u/ml. Abnormally elevated levels (greater than or equal to 75 u/ml) were found in most of the patients with Hashimoto's thyroiditis (94.1%) or idiopathic myxoedema (86.7%), in the majority (75.0%) of those with Graves' disease and only in a minority of those with other thyroid disorders. The percentage of positive sera by haemagglutination was very similar in all groups to that of abnormal values observed in the radioassay. Direct comparison of parallel tests on a total of 631 sera revealed a highly significant correlation (r = 0.91, P less than 0.001) between the two methods, but elevated antibody titres by haemagglutination were found in some sera with negative radioassays. All these sera were from a single patient with thyroid carcinoma associated with Hashimoto's thyroiditis and had elevated levels of anti-thyroglobulin (anti-Tg) antibodies. Evidence that such discrepancies were due to anti-Tg antibodies reacting with microsomal-bound Tg was provided by the demonstration that the haemagglutination produced by these sera could be completely inhibited by the addition of Tg. A similar inhibition was observed with two rabbit antisera to human Tg, but not with sera from patients with thyroid autoimmune disorders containing high levels of anti-microsomal anti-bodies.     

Marked increase of CD5 + B cells in hyperthyroid Graves' disease

We examined the proportions of B lymphocytes bearing CD5 cell surface antigen (CD5+ B cells), which are capable of making autoantibodies, in peripheral blood from patients with various thyroid diseases. The level of CD5+ B cells was markedly increased (>9.0%) above the normal range (0.5-7.7%) in untreated, hyperthyroid patients with Graves' disease, although about 10% of the patients had no detectable serum thyroid-stimulating hormone (TSH) receptor antibody (TRAb). However, the levels of CD5+ B cells were normal in untreated patients with destructive thyrotoxicosis due to aggravation of Hashimoto's thyroiditis or subacute thyroiditis. In patients with stimulated hyperthyroid Graves' disease the levels of CD5+ B cells were correlated with those of thyroid hormones and TRAb, all significantly increased. However, once hyperthyroidism was controlled by anti-thyroid drugs, CD5+ B cells were decreased, followed in turn by reduction of TRAb. We conclude that the proportion of CD5+ B cells is useful as a therapeutic index and for diagnosis of Graves' disease and its differentiation from destruction-induced thyrotoxicosis.     

Evidence for autoimmune mechanisms in the evolution of invasive fibrous thyroiditis (Riedel's struma)

The etiology of Riedel's invasive fibrous thyroiditis, a rare disorder confused in the past with the more common fibrous variant of Hashimoto's disease, has remained obscure. However, the presence of mononuclear cells in the fibrosclerotic process and the detection of autoantibodies directed against thyroid-specific antigens in a large proportion of patients with invasive fibrous thyroiditis favor an autoimmune pathogenesis of invasive fibrous thyroiditis. Further, an association between invasive fibrous thyroiditis and Hashimoto's thyroiditis has been suggested. Here we report the first two patients in whom invasive fibrous thyroiditis evolved from antecedent Graves' disease, documented by the presence of thyroid dysfunction, bilateral ophthalmopathy, and thyrotropin receptor stimulating autoantibodies. The diagnosis of invasive fibrous thyroiditis was established in both instances on the basis of the established histopathological criteria. The presence of extensive mononuclear cell infiltration within the invasive fibrosclerotic process in these two patients, the close relationship between thyroid-specific autoantibodies, inflammatory parameters, and disease activity, and the response to glucocorticoid therapy all suggest the existence of a link between Graves' disease and invasive fibrous thyroditis. These findings support the notion of autoimmune mechanisms playing a role in the pathogenesis of Riedel's invasive fibrous thyroiditis.Abbreviation IFT invasive fibrous thyroiditis Correspondence to: A.E. Heufelder     

Thyroid follicular cell function after non-lethal complement membrane attack

Terminal complement complexes have been identified around thyroid follicles in Graves' disease and Hashimoto's thyroiditis, and the concentrations of such complexes are increased in the sera of these patients, suggesting a role for complement activation and membrane attack complexes (MAC) in autoimmune thyroiditis. This has been investigated further using cultured human and rat thyroid cells. Thyrocytes were resistant to lysis by homologous complement, in contrast to the effects of heterologous (rabbit) complement. The formation of non-lethal amounts of MAC, using reactive lysis or classical pathway activation, significantly reduced cAMP production by these cells in response to thyroid-stimulating hormone (TSH) (P less than 0.01); similar effects were seen with thyroid-stimulating antibodies. Thyroid cells were able to recover rapidly from complement attack after washing and incubation for 30 min. Non-lethal MAC formation also resulted in reactive oxygen metabolite production, detected by luminol-dependent chemiluminescence in three out of five thyroid cell preparations tested. Ionomycin, but not TSH, also stimulated reactive oxygen metabolite production. These results suggest that repeated or continuous sub-lethal complement attack on thyroid cells may exacerbate hypothyroidism in Hashimoto's thyroiditis, or partially counter the effects of thyroid-stimulating antibodies in Graves' disease. Furthermore, the production of reactive oxygen metabolites in these circumstances could increase the intra-thyroidal inflammatory response; oxygen radical scavenging by anti-thyroid drugs (which are concentrated by thyrocytes) may account in part for the amelioration of thyroiditis observed with such treatment.     

Thyroid peroxidase antibodies in children with autoimmune thyroiditis.

AIMS: To compare the prevalence of thyroid peroxidase antibodies in 25 children with autoimmune thyroid disorders and in 41 children and young adults with type 1 diabetes, and to test the prevalence of thyrotropin receptor antibodies. METHODS: Two commercially available radioimmunoassays for antibodies to thyroid peroxidase, a commercially available agglutination test of particles coated with thyroid microsomal antigens, and a radioimmunoassay for thyrotropin receptor antibodies were used. Patients and controls were studied. RESULTS: One of the radioimmunoassays detected thyroid peroxidase antibodies not only in all children with autoimmune thyroid disorders and children and young adults with type 1 diabetes and thyroid microsomal antibodies, but also in 20% of healthy control children without microsomal antibodies. With this thyroid peroxidase assay and with microsomal agglutination, 94% of the children with autoimmune thyroiditis, 71% of those with Graves' disease, and over 90% of those with type 1 diabetes and thyroid dysfunction tested positive. In the other radioimmunoassay for thyroid peroxidase antibodies thyroid peroxidase antibody titres in half or more of the children with microsomal antibodies failed to reach the level of positivity given by the producers. Eighty five percent of children with Graves' disease and 71% of those with autoimmune thyroiditis had thyrotropin receptor antibodies but so did 35% of children studied for other endocrinological disorders such as delayed growth or puberty. CONCLUSIONS: Testing patients with well characterised disorders of thyroid function and with other endocrine disorders is important in evaluating the efficacy of new diagnostic tests for thyroid autoantibodies.     

Thyroid function tests

About 80% of thyroid disease consists of thyroid-specific autoimmune diseases, Hashimoto's disease and Grave's disease. To diagnose thyroid diseases, testings for (1) thyroid function and (2) pathogenetic autoantibodies are indispensable. To assess thyroid function, serum hormone concentrations, such as TSH, FT4 and FT3 are measured. Among these hormones, serum TSH concentrations are the most reliable and informative regarding thyroid function, correcting indicating a hyperthyroid, euthyroid or hypothyroid state. Therefore, TSH measurement appears to be the first choice in selecting the hormone determination. Reference intervals for normal healthy subjects of TSH are around 0.4-5.0 microU/ml. The second choice for thyroid function assessment are FT4 which supersedes total T4(TT4). TT4 is affected by changes in serum thyroid hormone binding proteins(TBG, TTR, Albumin). For example, euthyroid pregnant women whose serum TBG are physiologically higher than those of non-pregnant women show augmentation of TT4. However, FT4 depicts within reference intervals, although measurement of FT4 alone is unable to detect any abnormality of thyroid hormone binding proteins. According to its plasma concentration and binding affinity, FT3 measurement deserves no more significance than T3. Another important test for thyroid diseases is to detect serum autoantibodies against thyroid tissues, such as TgAb, TPOAb. Much more important is TSH receptor antibody which differentiates Graves' disease from Hashimoto's thyroiditis. In patients who show hyperthyroidism and some very uncommon hypothyroidism, TSH receptor antibodies should be measured. Three indicators are available as routine tests; TRAb measured by radioreceptor assay; TSAb determined by bioassay using cultured porcine thyroid cells. Usually, TRAb activity clinically correlates well with TSAb. TSBAb was initially discovered in patients with severe hypothyroidism with atrophic thyroid gland. TSBAb blocks thyroid stimulating activity of TSH and consequently causes severe hypothyroidism. TRAb and TSAb are very useful to diagnose and follow patients with Grave's disease.