Immunological of the Thyrotropin Receptor

Antibodies to the thyrotropin receptor appear to he responsible for hyperthyroidism in Graves disease. The antibodies, described as thyroid-stimulating antibodies (TSAb) mimic the effects of thyrotropin (TSH) by binding to the TSH receptor and activating adenylate cyclase. TSAb consist of an electrophoretically heterogeneous population of IgG and the thyroid-stimulating site is formed by combination of heavy and light chains in the Fab part of the molecule. Binding studies indicate that the TSAb molecule interacts monovalently with membrane bound TSH receptors and that TSAb consists of an antibody population which shows a restricted heterogeneity with regard to TSH receptor affinity. Studies in patients with Graves disease and hyperthyroidism indicate that the levels of TSAb correlate well with thyroidal iodine uptake and the absence of pituitary control of thyroid function. However in some patients with ophthalmic Graves' disease or autoimmune thyroiditis there is evidence of serum antibodies which interact with the TSH receptor but are unable to stimulate thyroid function.     

Immunology of the thyrotropin receptor.

Antibodies to the thyrotropin receptor appear to be responsible for hyperthyroidism in Graves' disease. The antibodies, described as thyroid-stimulating antibodies (TSAb) mimic the effects of thyrotropin (TSH) by binding to the TSH receptor and activating adenylate cyclase. TSAb consist of an electrophoretically heterogeneous population of IgG and the thyroid-stimulating site is formed by combination of heavy and light chains in the Fab part of the molecule. Binding studies indicate that the TSAb molecule interacts monovalently with membrane bound TSH receptors and that TSAb consists of an antibody population which shows a restricted heterogeneity with regard to TSH receptor affinity. Studies in patients with Graves' disease and hyperthyroidism indicate that the levels of TSAb correlate well with thyroidal iodine uptake and the absence of pituitary control of thyroid function. However in some patients with ophthalmic Graves' disease or autoimmune thyroiditis there is evidence of serum antibodies which interact with the TSH receptor but are unable to stimulate thyroid function.     

Generation of a transgenic animal model of hyperthyroid Graves' disease

Graves' disease (GD) is an organ-specific autoimmune disease characterized by hyperthyroidism. Agonistic anti-thyrotropin receptor antibodies (thyroid-stimulating antibodies, TSAb), which mimic the thyrotropin (TSH) action, are thought to cause GD. The precise immunological mechanism of TSAb production, however, remains elusive. Previous immunization approaches using TSH receptor led to transient hyperthyroidism, but did not seem sufficient for comprehensive understanding of the development of autoimmune responses. To create GD-related autoimmunity in mice, we here generated TSAb-transgenic mice in which a patient-derived TSAb is expressed in B cells. Expression of the human TSAb in mice resulted in various manifestations of hyperthyroidism including increased free thyroxine levels with concomitantly decreased TSH levels, increased thyroid uptake of technetium pertechnetate, hyperthermia and thyroid hyperplasia. We found a correlation between the serum levels of human TSAb immunoglobulin and free thyroxine. In addition, conventional B cells expressing the TSAb were partially deleted in the periphery while B1 cells expressing the TSAb persisted and accumulated in the peritoneal cavity, a finding consistent with previous demonstrations that the maintenance of B1 cells plays an important role in the development of autoimmune diseases. Thus, our transgenic mouse may provide a novel and useful animal model for elucidating the pathogenesis and pathophysiology of GD.     

Graves病患者治疗前、后血清甲状腺刺激抗体和TSH结合抑制免疫球蛋白活性的观察

本文研究了Ｇｒａｖｅｓ病（ＧＤ）患者在抗甲状腺药物（ＡＴＤ）治疗前、后血清甲状腺刺激抗体（ＴＳＡｂ）和ＴＳＨ结合抑制免疫球蛋白（ＴＢＩＩ）的变化，发现治疗前ＴＳＡｂ和ＴＢＩＩ的检出率分别为９１．７％和７９．２％，治疗后两抗体的活性及阳性率均显著下降，表明抗甲状腺药可改善ＧＤ患者的免疫异常。ＴＳＡｂ和ＴＢＩＩ活性不相关，提示ＴＳＨ受体抗体（ＴＲＡｂ）具有异质性。ＴＳＡｂ和ＴＢＩＩ活性与血清甲状腺激素水平无相关关系，说明体外测定的ＴＳＡｂ或／和ＴＢＩＩ活性并不能完全反映甲亢的严重程度。     

Thyroid-stimulating antibodies in patients with long-term remission of Graves' hyperthyroidism

Summary The persistence of TSH receptor antibodies in Graves' disease despite the remission of hyperthyroidism has been described. Our study was designed to evaluate whether this extends to functionally active stimulators of the thyroid, since the occurrence of thyroid-stimulating antibodies (TSAb) in a euthyroid patient could well have important implications on our understanding of the pathogenetic role of such autoantibodies. Forty-four patients with a previous history of Graves' hyperthyroidism were reexamined after having been in long-lasting remission for 3 to 35 years (mean 8 years). Of the patients 16 had been treated by radioiodine, 17 by surgery, and 11 exclusively by antithyroid drugs. The determination of TSAb was based on T3 release from thyroid tissue in vitro to document the final response to these immunoglobulins. TSH-binding inhibiting immunoglobulins (TBII) were evaluated by a radioreceptor assay.TSAb were highly elevated in three of the 44 patients. These three patients showed a normal TSH response to i.v. TRH, suffered from endocrine ophthalmopathy, and had been treated by radioiodine for hyperthyroidism. TBII were found positive in seven patients including the three patients mentioned. The majority of patients positive for TSAb or TBII had been treated by radioiodine and none exclusively by antithyroid drugs.In conclusion, not only TBII but also T3 release-stimulating antibodies may occur in a minority of patients with long-term remission of Graves' hyperthyroidism. However, an absence of hyperthyroidism in these patients despite the presence of such thyroid stimulators seems to be only possible in association with a lack of functional responsiveness of the target organ due to previous administration of destructive therapies. Moreover, a major role of TBII in the absence of TSAb representing stimulatory inactive autoantibodies to the maintenance of remission was not apparent.Abbreviations cAMP cyclic adenosine monophosphate - T3 triiodothyronine - T4 tetraiodothyronine - TBII TSH-binding inhibiting immunoglobulins - TRH TSH-releasing hormone - TSAb thyroid-stimulating antibodies - TSH thyroidstimulating hormone     

Thyroid-stimulating hormone receptor and its role in Graves' disease

The thyroid-stimulating hormone (TSH, or thyrotropin) receptor (TSHR) mediates the activating action of TSH to the thyroid gland, resulting in the growth and proliferation of thyrocytes and thyroid hormone production. In Graves' disease, thyroid-stimulating autoantibodies can mimic TSH action and stimulate thyroid cells. This leads to hyperthyroidism and abnormal overproduction of thyroid hormone. TSHR-antibodies-binding epitopes on the receptor molecule are well studied. Mechanism of TSHR-autoantibodies production is more or less clear but a susceptibility gene, which is linked to their production, is still unknown. Genetic studies show no linkage between the TSHR gene and Graves' disease. Among three common polymorphisms in the TSHR gene, only the D727E germline polymorphism in the cytoplasmic tail of the receptor showed an association with the disease, and this association is weak. The absence of a strong genetic effect of the TSHR polymorphisms in such a common and complex disorder as Graves' disease may be explained by a high degree of evolutionary conservation in TSHR. This can be shown by naturally existing germline and somatic mutations in the TSHR gene that cause various types of nonautoimmune and hereditary thyroid disease.     

Adenovirus encoding the thyrotropin receptor A-subunit improves the efficacy of dendritic cell-induced Graves' hyperthyroidism in mice

Stimulating the immune system by in vivo expression of the thyrotropin receptor (TSHR) is an efficient means to induce Graves' disease experimentally. For example, BALB/c mice injected with dendritic cells (DCs) infected with adenovirus encoding the full-length TSHR (AdTSHR) develop hyperthyroidism, albeit at a low incidence (36%). Recent observations suggest that the shed TSHR A-subunit, rather than the full-length receptor, is the autoantigen responsible for initiating/enhancing immune responses leading to thyroid stimulating antibodies (TSAb) and hyperthyroidism. Therefore, we attempted to improve the efficacy of the DC-based approach for Graves' disease using adenovirus encoding the TSHR A-subunit (AdTSHR289). Three injections of DCs infected with AdTSHR289 induced hyperthyroidism in 70% of BALB/c mice, approximately twice the disease induction rate with AdTSHR. TSAb activity was detected in most hyperthyroid mice, whereas virtually all immunized mice developed antibodies that inhibit [125I]TSH binding to the TSHR or recognize linear or conformational epitopes on the TSHR. TSHR antibodies were of IgG1 and IgG2a, indicating mixed T-helper type 1 (Th1)/Th2 immune responses. In conclusion, immunization with DC infected with adenovirus expressing the TSHR A-subunit is a highly efficient protocol to induce Graves' hyperthyroidism in BALB/c mice. This improved model will permit studies of the pathogenic role and therapeutic potential of DCs in Graves' hyperthyroidism.     

Un nouveau dosage des anticorps anti-récepteur de la TSH : le TRAK humain. Intérêt diagnostique et pronostique dans la maladie de Basedow

Hyperthyroidism in Gravesˈdisease is attributable to the presence of TSH-receptor antibodies : thyroid stimulating antibodies (TSAb) and TSH binding inhibiting immunoglobulins (TBII). A new assay for TBII using a recombinant human receptor is now commercially available (Dynotest TRAK human, Brahms). We have evaluated its analytical and clinical performances in the diagnostic and in the follow-up of Gravesˈdisease. We have also compared them to those obtained for porcine TRAK (TRAK assay) and for TSAb measured on cellular cultures. We studied here 154 patients with Gravesˈdisease before and after treatment with antithyroid drugs (ATD). The performances of TBII assay with human TRAK were higher than those obtained for porcine TRAK and sometimes for TSAb. Thus TBII shoud be now measured with this commercially kit. Moreover, this new assay can advantageously replace TSAb measurement in the diagnosis and in the follow-up of Gravesˈpatients treated with ATD.     

A Novel Mouse Model of Graves’ Disease: Implications for a Role of Aberrant MHC Class II Expression in its Pathogenesis

Mice immunized with fibroblasts expressing an MHC class II molecule and human thyrotropin receptor (TSHR), but not either alone, develop major features characteristic of Graves’ disease (GD), such as thyroid-stimulating autoantibodies directed against TSHR, increased serum thyroid hormone levels, and enlarged thyroid glands. The results indicate the need for the simultaneous expression of a class II molecule and the TSHR on the surface of the fibroblasts to develop stimulating anti-TSHR antibodies and fullblown GD in our model. A T cell line established from a mouse with hyperthyroidism proliferates in response to fibroblasts expressing a class II molecule and TSHR, but not to the fibroblasts expressing only TSHR, indicating that the class II molecules on the fibroblasts present TSHR-derived peptide(s) to T cells. These results strongly suggest that the acquisition of antigen-presenting ability by thyrocytes can lead to the induction or progression of GD. We identified a T cell epitope of TSHR by the proliferative response of spleen cells from mice immunized with fibroblasts expressing a class II molecule and TSHR to 80 overlapping peptides spanning the extracellular domain of human TSHR. The identification of a major T cell epitope provides an important clue to a novel therapy of GD.     

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.     

Biological activity of anti-thyrotropin anti-idiotypic antibody

Rabbit anti-rat anti-human thyrotropin anti-idiotypic antibodies have been raised. These antibodies were active at the thyrotropin (TSH) receptor, in that they inhibited ¹²⁵I-labeled bovine TSH binding to thyroid plasma membranes, stimulated adenylate cyclase activity through a guanyl nucleotide-dependent mechanism, augmented radioiodide transport into isolated porcine thyroid follicular cells and induced such cultured cells to organize into follicles. Aside from substantiating the expectation that anti-hormone anti-idiotypic antibodies may possess properties of the original hormone, this work raised the possibility that thyroid-stimulating antibodies which cause the hyperthyroidism of Graves' disease may be anti-TSH anti-idiotypic antibodies.     

Important considerations in the management of Graves’ disease in pregnant women

Graves’ disease is an autoimmune disorder in which autoantibodies to the thyroid-stimulating hormone receptor cause hyperthyroidism through unregulated stimulation of the thyroid-stimulating hormone receptor. Effective management of Graves’ disease in pregnancy must address the competing fetal and maternal priorities of controlling hyperthyroidism in the mother on the one hand, and on the other, minimizing the impact of maternal disease and antithyroid drugs on the well-being of the fetus. Optimal strategies for achieving this intricate balance are currently a source of continued debate among thyroid experts and studies in recent decades are now providing greater clarity into the risk posed to the unborn baby by the combination of biochemical, immunological and pharmacological hazards arising from Graves’ disease and its therapy. This review summarizes the current best practice and highlights important considerations and areas of uncertainty in the management of Graves’ disease in pregnant women.     

Effect of antithyroid drugs on the occurrence of antibodies against type 2 deiodinase (DIO2), which are involved in hyperthyroid Graves’ disease influencing the therapeutic efficacy

Clinical and Experimental Medicine - Graves’ disease is an organ-specific autoimmune disease with hyperthyroidism, diffuse goiter and autoantibodies against TSH receptor, thyroid peroxidase...     

联合应用抗甲状腺药物和甲状腺激素治疗Graves病的效果评价

本文研究抗甲状腺药物（ＡＴＤ）单独或与甲状腺激素联合应用，对Ｇｒａｖｅｓ病（ＧＤ）病情演变和转归的作用。联合用药组血清甲状腺刺激抗体（ＴＳＡｂ）下降的幅度明显大于单独应用ＡＴＤ组，其血清ＴＳＨ水平、药物性甲减的发病率以及停药后甲亢的复发率均显著低于单独用药组。提示ＡＴＤ与甲状腺制剂联合应用对ＧＤ具有更好的治疗效果。     

Clinical applications of TSH receptor antibodies in thyroid diseases

The cloning and sequencing of thyroid-stimulating hormone (TSH) receptor (TSHR), combined with advances in molecular techniques, have facilitated the understanding of the interaction of the TSHR antibodies (TSHRAbs) with the TSHR at the molecular level and have allowed the delineation of their clinical role. TSHRAbs in vivo are functionally heterogeneous; the stimulating TSHRAbs cause hyperthyroidism and diffuse goiter in patients with Graves' disease, whereas, the blocking TSHRAbs cause hypothyroidism in some patients with autoimmune hypothyroidism and are the cause of transient neonatal hypothyroidism. Measuring TSHRAbs has potential clinical implications in differential diagnosis of Graves' disease, predicting the outcome of Graves' disease after antithyroid drug treatment, and predicting the fetal/neonatal hyperthyroidism or neonatal hypothyroidism. The existence of epitope heterogeneity in a patient, i.e., of stimulating TSHRAbs with epitopes other than on the N-terminal region of the extracellular domain, is significantly associated with favorable long-term clinical response to antithyroid drug treatment. Measuring these subtypes for thyroid-stimulating antibody (TSAb) has potential clinical implications, for example, in predicting responsiveness to treatment in untreated patients with Graves' disease.     

Modulation of Fas-mediated apoptosis of human thyroid epithelial cells by IgG from patients with Graves' disease (GD) and idiopathic myxoedema

The expression of two autoimmune thyroid diseases, GD and idiopathic myxoedema, is associated with antibodies to the thyroid-stimulating hormone (TSH) receptor. Thyroid stimulating antibodies (TSAb) in GD are TSH agonists and cause hyperthyroidism as well as goitre, whereas thyroid stimulation blocking antibodies (TSBAb) in idiopathic myxoedema are TSH antagonists and cause hypothyroidism and thyroid atrophy. We investigated the effect of antibodies to TSH receptor on Fas-mediated apoptosis of thyroid epithelial cells (thyrocytes). Human IgG was isolated from healthy donors, patients with GD and idiopathic myxoedema. Human thyrocytes were obtained from surgical specimens. Thyrocytes were cultured in the presence or absence of human IgG with or without interferon-gamma (IFN-γ) or IL-1β for a specified time. After incubation, we examined the level of cAMP in cultured supernatants and both Fas and Bcl-2 expression on thyrocytes. In addition, we examined anti-Fas-mediated apoptosis of thyrocytes. Fas expression on thyrocytes was significantly down-regulated by Graves' IgG and TSH, although idiopathic myxoedema IgG did not affect Fas expression on thyrocytes. Idiopathic myxoedema IgG abrogated the effect of TSH on both cAMP production and inhibition of Fas expression on thyrocytes. Treatment of thyrocytes with IL-1β or IFN-γ caused a marked augmentation of Fas expression on thyrocytes. The increase of Fas expression of thyrocytes induced by IL-1β or IFN-γ was significantly suppressed in the presence of TSH or Graves' IgG. Anti-Fas-induced apoptosis of thyrocytes was observed in thyrocytes treated with IL-1β or IFN-γ, but was markedly inhibited in the presence of TSH or Graves' IgG. Furthermore, idiopathic myxoedema IgG abrogated most of the inhibitory effect of TSH on Fas-mediated apoptosis of thyrocytes treated with IL-1β or IFN-γ. Bcl-2 expression of thyrocytes did not change after stimulation with TSH, Graves' IgG, idiopathic myxoedema IgG, IL-1β or IFN-γ. These results suggest that TSAb found in Graves' patients may be potentially involved in the development of goitre by inhibition of Fas-mediated apoptosis of thyrocytes. In addition, TSBAb inhibit the action of TSH and increase the sensitivity toward Fas-mediated apoptosis of thyrocytes, inducing thyroid atrophy seen in patients with idiopathic myxoedema.     

A novel mouse model of Graves' disease: implications for a role of aberrant MHC class II expression in its pathogenesis

Mice immunized with fibroblasts expressing an MHC class II molecule and human thyrotropin receptor (TSHR), but not either alone, develop major features characteristic of Graves' disease (GD), such as thyroid-stimulating autoantibodies directed against TSHR, increased serum thyroid hormone levels, and enlarged thyroid glands. The results indicate the need for the simultaneous expression of a class II molecule and the TSHR on the surface of the fibroblasts to develop stimulating anti-TSHR antibodies and full-blown GD in our model. A T cell line established from a mouse with hyperthyroidism proliferates in response to fibroblasts expressing a class II molecule and TSHR, but not to the fibroblasts expressing only TSHR, indicating that the class II molecules on the fibroblasts present TSHR-derived peptide(s) to T cells. These results strongly suggest that the acquisition of antigen-presenting ability by thyrocytes can lead to the induction or progression of GD. We identified a T cell epitope of TSHR by the proliferative response of spleen cells from mice immunized with fibroblasts expressing a class II molecule and TSHR to 80 overlapping peptides spanning the extracellular domain of human TSHR. The identification of a major T cell epitope provides an important clue to a novel therapy of GD.     

Graves病患者甲状腺功能与血清胱抑素C的相关性研究及其临床应用价值讨论

目的 回顾性研究正常对照人群及弥漫性毒性甲状腺肿(Graves病)患者治疗前后的甲状腺激素水平及其与血清胱抑素C水平的关系.方法 选择2013年1月至2015年9月于本院就诊的Graves病患者共185例,另选取甲状腺功能正常者24例为对照组,所有患者均行甲状腺功能(FT3、FT4、TSH)及胱抑素C(CysC)检测,并筛选其中检测后接受了碘-131治疗的患者19例,在其治疗后再次检测甲状腺功能(FT3、FT4、TSH)及胱抑素C(CysC),对比并分析结果.结果Graves病组患者胱抑素C水平明显高于对照组水平(P<0.05);Graves病组患者甲状腺激素水平与胱抑素C检测结果呈正相关,FT3、FT4与胱抑素C的相关系数分别为rs=0.69和rs=0.66(均P<0.05);Graves病患者治疗后其甲状腺激素水平与胱抑素C水平均较治疗前显著下降,两组差异具有统计学意义,治疗后与对照组比较,差异无统计学意义.结论Graves病是胱抑素C升高的重要原因;Graves病患者治疗前后胱抑素C水平与甲状腺激素水平水平呈正相关,提示在排除肾脏疾病的前提下,胱抑素C可反映甲状腺功能状态.     

Prognostic value of thyroid stimulating antibodies and TSH-binding inhibiting immunoglobulins in the follow-up of Graves' disease

Summary The prognostic value of the determinations of autoantibodies in Graves' disease is still questionable. So far, the role of different assay procedures used has not been intensively investigated. We simultaneously applied two different techniques, a radioreceptor assay and a T3 releasing in vitro assay, in the follow-up of patients with Graves' disease to directly compare the course of the antibody activities determined by these assays and to find out a prognostic significance of the composition of the antibody spectrum present. The initial activities of thyroid stimulating antibodies (TSAb) and TSH-binding inhibiting immunoglobulins (TBII) were not significantly correlated in patients before treatment. During a 12-month antithyroid medication antibody titres showed a concordant course in the majority of patients. In 6 of 25 patients, however, a discordant behaviour was clearly documented including dose-response curves. At the end of treatment, the patients could be divided into three groups: group I included 5 patients positive for both TSAb and TBII, group II 6 patients positive for TBII and negative for TSAb and group III 14 patients negative for both of them. During the following survey of 18 months all patients of group I, 2 patients of group II and 6 patients of group III experienced a relapse of hyperthyroidism. In conclusion, TSAb and TBII activities dissociate in some patients during antithyroid drug therapy. For the individual patient, the disappearance of both TSAb and TBII was no certain indicator for a longstanding remission of Graves' hyperthyroidism. The persistence of TSAb seems to be more reliably associated with persisting or rapidly relapsing disease than the persistence of TBII.Abbreviations cAMP Cyclic Adenosine Monophosphate - GD Graves' disease - T3 Triiodothyronine - T4 Tetraiodothyronine - TBII TSH-binding inhibiting immunoglobulins - TRH TSH releasing hormone - TSAb Thyroid stimulating antibodies - TSH Thyroid stimulating hormone     

Analysis of circulating thyroid-stimulating activities in pregnant women with Graves' disease: differential measurement of activities induced by TSH receptor antibody and hCG]

Thyrotoxicosis in Graves' disease is often aggravated in early pregnancy and this aggravation is associated with postpartum relapse of thyrotoxicosis. To examine whether thyroid-stimulating TSH receptor antibody (TSAb) or human chorionic gonadotropin (hCG), which also has thyroid-stimulating activity (TSA), is responsible for this early aggravation, the respective TSA due to TSAb or hCG were evaluated with a sensitive cAMP accumulation assay using FRTL-5 cells. TSA, which was detectable in all of 11 women in normal early pregnancy, correlated positively with serum hCG level, but was abolished completely by the pretreatment of serum samples with the solid-phase hCG antibody coupled with Sepharose-4B. Total TSA in the model samples of mixture of Graves' and pregnant sera (Gr + Preg), was reduced by the pretreatment with the solid-phase antibody, just corresponding with the reduction in hCG-induced TSA. Total TSA in early pregnant sera in 15 patients with Graves' disease, decreased significantly but was still positive even by the pretreatment with the hCG antibody. Pregnancy-associated changes in TSA was examined serially in a patient with Graves' disease, and hCG-induced TSA increased predominantly along with the serum thyroid hormone in early aggravation period. These data indicate that (1) the respective TSA due to TSAb or hCG can be differentially measured by using the solid-phase hCG antibody and (2) hCG plays an important role for aggravation of Graves' thyrotoxicosis in early pregnancy.