Identification of Two Different Phenotypes of Patients with Amiodarone-Induced Thyrotoxicosis and Positive Thyrotropin Receptor Antibody Tests.

Introduction: Serum thyrotropin (TSH) receptor antibodies (TRAbs) are occasionally found in patients with amiodarone-induced thyrotoxicosis (AIT), and usually point to a diagnosis of type 1 AIT (AIT1) due to Graves' disease (GD). However, the TRAb role and function in AIT have not been clarified. Methods: A retrospective cohort study of 309 AIT patients followed at a single academic center over a 30-year period. AIT TRAb-positive patients (n = 21, 7% of all cases) constituted the study group; control groups consisted of type 2 AIT (AIT2) TRAb-negative patients (n = 233), and 100 non-AIT patients with GD. Clinical and biochemical data at diagnosis and during the course of disease were compared. Histological samples of patients who had total thyroidectomy were reviewed. Stored serum samples were used for a functional assay of TRAb class G immunoglobulins (IgGs) in Chinese hamster ovary (CHO) cells stably transfected with complementary DNA encoding for the TSH receptor. Results: TRAb-positive patients were grouped according to color flow Doppler sonography, radioactive iodine thyroid uptake, and duration of amiodarone therapy before thyrotoxicosis in type 1 (n = 9, 43%; TRAb1) or type 2 (n = 12, 57%; TRAb2) AIT. TRAb1 patients had clinical and biochemical features indistinguishable from GD controls, and were responsive to methimazole. Conversely, TRAb2 patients had clinical features similar to AIT2 controls, and were responsive to glucocorticoids, but not to methimazole. The CHO cell functional assay demonstrated that TRAb1 IgGs had a stimulatory effect on cyclic AMP production, which was absent in TRAb2 IgGs. Pathology in TRAb1 showed hyperplastic thyroid follicles and mild lymphocyte infiltration, reflecting thyroid stimulation. On the contrary, TRAb2 samples revealed follicle destruction, macrophage infiltration, and sometimes fibrosis, consistent with a destructive process. Conclusions: Almost 60% of TRAb-positive AIT patients had a destructive thyroiditis. TRAb-positive tests in AIT patients do thus not necessarily imply a diagnosis of GD and AIT1, and should be evaluated in the clinical and biochemical setting of each AIT patient and confirmed by measuring thyroid-stimulating immunoglobulins.

A pilot study on the beneficial effects of additional selenium supplementation to methimazole for treating patients with Graves' disease

Background/aim: The aim of this study was to assess the effect of a combination use of methimazole (MMI) and selenium (Se) in the treatment of Graves' disease (GD). Materials and methods: A total of 103 newly diagnosed hyperthyroidism patients were randomized to MMI and MMI + Se combination groups. After treatment for 6 months, the levels of triiodothyronine (FT3), free thyroxine (FT4), thyrotropin receptor antibody (TRAb), thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TGAb) were observed. An in vitro culture model of thyroid cells was established and the protein expression and mRNA levels of TRAb, TPOAb, and TGAb were determined by western blot and RT-PCR. Results: A significant decrease in the levels of FT3, FT4, TRAb, TPOAb, and TGAb were observed in both groups along with a marked increase in TSH levels. Furthermore, the in vitro experiments showed that the protein expression and mRNA levels of TRAb, TPOAb, and TGAb decreased significantly. Also, compared to the MMI group, there was a greater improvement of these indices in the MMI + Se group. Conclusion: We suggest that the combined use of MMI and Se could improve the thyroid activity in patients, which may provide an effective therapy for the treatment of GD in clinical settings.

POSITIVE THYROTROPIN RECEPTOR ANTIBODIES IN PATIENTS WITH TRANSIENT THYROTOXICOSIS.

OBJECTIVE: Thyrotropin (TSH) receptor antibody (TRAb) testing is considered accurate for the diagnosis of Graves disease (GD) and has been identified rarely in thyrotoxic patients without GD. We describe 4 patients with transient thyrotoxicosis and positive TRAb to highlight this clinical possibility. METHODS: Patient demographics, symptoms, laboratory findings, and time to resolution of thyrotoxicosis are summarized. TRAb testing was performed by either a third-generation thyrotropin-binding inhibitory immunoglobulin (TBII) competitive-binding assay or a thyroid-stimulating immunoglobulin (TSI) bioassay from either Mayo Clinic Laboratory or Quest Diagnostics. RESULTS: Four patients with transient thyrotoxicosis and positive TRAb testing were identified. Of these, three were female, and the median age was 44 years (range, 25 to 49 years). Median symptom duration at evaluation was 6.5 weeks (range, 3 to 12 weeks). No patient had any clinical manifestations unique to GD or exposure to biotin, thyroid hormone, supplements, iodine, or relevant medications. The TSH was <0.1 mIU/L in all patients. Three patients had a positive TSI, which was elevated less than twice the upper limit of the reference range in all cases, and 1 patient had a strongly positive TBII. None of the patients were treated with thionamides or radioactive iodine. Spontaneous resolution occurred in all patients at a median of 5.5 weeks (range, 2 to 14.4 weeks). CONCLUSION: These cases demonstrate that TSI or TBII may be present in thyrotoxic patients with transient thyrotoxicosis. For clinically stable patients presenting without pathognomonic evidence of GD, mildly elevated TRAb results may require cautious interpretation, and alterative diagnostic testing or close monitoring should be considered. ABBREVIATIONS: cAMP = cyclic adenosine monophosphate; FT4 = free thyroxine; GD = Graves disease; TBII = thyrotropin-binding inhibitory immunoglobulin (also known as TBI); TRAb = thyrotropin receptor antibody; TSH = thyrotropin; TSHR = thyrotropin receptor; TSI = thyroid-stimulating immunoglobulin; TT3 = total triiodothyronine; TT4 = total thyroxine.

Serum Trace Elements Profile in Graves' Disease Patients with or without Orbitopathy in Northeast China.

OBJECTIVE: The purpose of the present study was to investigate serum trace elements in Graves' disease (GD) patients with or without orbitopathy in Northeast China. METHODS: Patients with newly diagnosed Graves' disease (HyGD) (n = 66), GD patients with euthyroid status or subclinical thyroidism after treatment (EUGD) (n = 55), GO patients with euthyroid status or subclinical thyroidism after treatment (GO) (n = 57), and normal controls (NC) (n = 66) were enrolled in this study. Serum trace elements were measured with ICP-MS. RESULTS: Serum selenium (Se) levels in EUGD group (median: 7.53 µg/dL), HyGD group (median: 6.76 µg/dL), and GO group (median: 7.40 µg/dL) were significantly lower than those in NC group (median: 9.20 µg/dL, all P < 0.01). Serum copper (Cu) levels in GO group (median: 95.93 µg/dL) were significantly lower than those in the NC group (median: 113.59 µg/dL, P = 0.015). After being adjusted for multivariables, thyroid-specific antibodies grade was associated with low Se levels. Hyperthyroidism and thyroid-specific antibodies grade were associated with high Cu levels. In addition, orbitopathy was associated with low Cu levels. CONCLUSIONS: Thyroid autoimmunity was associated with low Se levels. Hyperthyroidism and thyroid autoimmunity may be associated with relatively high serum Cu levels. Alternatively, ophthalmopathy may be related to low serum Cu levels.

Variable Effects of Dietary Selenium in Mice That Spontaneously Develop a Spectrum of Thyroid Autoantibodies.

Selenium (Se) is a critical element in thyroid function, and variable dietary Se intake influences immunity. Consequently, dietary Se could influence development of thyroid autoimmunity and provide an adjunct to treat autoimmune thyroid dysfunction. Nonobese diabetic (NOD).H2h4 mice spontaneously develop autoantibodies to thyroglobulin (Tg) and thyroid peroxidase (TPO). This mouse strain expressing a human thyroid-stimulating hormone receptor (TSHR) A-subunit transgene in the thyroid also develops pathogenic TSHR autoantibodies. In this report, we investigated whether dietary Se influences these immune processes. Male and female wild-type and transgenic NOD.H2h4 mice were maintained on normal-, low-, or high-Se (0.1, 0, or 1.0 mg/kg) rodent diets. After 4 months, Se serum levels were extremely low or significantly increased on 0 or 1.0 mg/kg Se, respectively. Varying Se intake affected Tg antibody (TgAb) levels after 2 (but not 4) months; conversely, TPO antibody (TPOAb) levels were altered by dietary Se after 4 (but not 2) months. These data correspond to the earlier development of TgAb than TPOAb in NOD.H2h4 mice. In males, TgAb levels were enhanced by high Se and in females by low Se intake. Se intake had no effect on pathogenic TSHR autoantibodies in TSHR transgenic NOD.H2h4 females. In conclusion, in susceptible NOD.H2h4 mice, we found no evidence that a higher dietary Se intake ameliorates thyroid autoimmunity by reducing autoantibodies to Tg, TPO, or the TSHR. Instead, our finding that low dietary Se potentiates the development of autoantibodies to Tg and TPO in females is consistent with reports in humans of an increased prevalence of autoimmune thyroiditis in low-Se regions.

Determinants of serum T4 and T3 at the time of diagnosis in nosological types of thyrotoxicosis: a population-based study.

OBJECTIVE: To characterize thyroid hormone levels at the time of diagnosis in the nosological types of thyrotoxicosis diagnosed in the population and to analyze determinants for serum thyroxine (T4) and tri-iodothyronine (T3). DESIGN: Population-based study of thyrotoxicosis at disease onset. METHODS: In the period 1997-2000, we prospectively identified all patients diagnosed with incident primary overt thyrotoxicosis in a Danish population cohort and classified patients into ten well-defined nosological types of disease (n=1082). Untreated levels of serum T3, T4, and T3:T4 ratio were compared and related to sex, age, level of iodine deficiency, smoking status, alcohol intake, iodine supplement use, co-morbidity, and TSH receptor antibodies (TRAbs) in multivariate models. RESULTS: Graves' disease (GD) patients had much higher levels of T3 and higher T3:T4 ratio at diagnosis compared with other thyrotoxic patients, but with a profound negative association between hormone levels and age. In GD, patients diagnosed in the area with more severe iodine deficiency had lower levels of T3 and T4. TRAb-negative GD patients had biochemically mild thyrotoxicosis. Higher age was also associated with lower degree of biochemical thyrotoxicosis in nodular toxic goiter. We found no association between serum T3 and T4 and sex, smoking habits, iodine supplements, alcohol intake, or co-morbidity in any type of thyrotoxicosis. CONCLUSIONS: The study gives new insight into the hormonal presentation of thyrotoxicosis and showed that young age, positive TRAb levels, but also residency in the area with higher iodine intake was positively associated with biochemical disruption in GD.

[Reference values for thyroid hormones in the population of pregnant women in Jaen (Spain)]. / Valores de referencia de hormonas tiroideas en la población de mujeres gestantes de Jaén.

OBJECTIVE: To evaluate thyroid function in the three trimesters of pregnancy in healthy women taking iodine and to define the reference ranges of normality in this population. DESIGN: Descriptive study of pregnant women to define the ranges of normality of thyroid hormones in this population. SETTING: Jaen and Osuna (Spain). POPULATION: Healthy pregnant women. METHODS: Thyroid hormone determination in the three trimesters of pregnancy in healthy women taking iodine supplements. RESULTS: A total of 429 pregnant women taking iodine supplements to maintain urinary iodine levels within the normal range were included. T4-l levels were between 0.60 and 1.06 in the first trimester, between 0.43 and 0.85 ng/dl in the second and between 0.40 and 0.82 ng/dl in the third. Thyroid stimulating hormone (TSH) reference values were between 0.23 and 4.18µUI/ml in the first trimester, 1.78 and 3.89µUI/ml in the second and 2.01 and 4.30µUI/ml in the third. T3-l values were between 2.33 and 3.84 pg/ml in the first trimester, between 2.04 and 3.51 pg/ml in the second and between 1.99 and 3.46 pg/ml in the third. CONCLUSION: Bearing the 3rd and 97th percentiles in mind, the reference ranges in our population were far below those recommended by our reference laboratory. In view of these results, these values should be redefined to avoid incorrect diagnoses of hyperthyroxinemia in healthy pregnant women.

Valores de referencia de hormonas tiroideas en la población de mujeres gestantes de Jaén / Reference values for thyroid hormones in the population of pregnant women in jaen (Spain)

Objetivo Valorar la función tiroidea en los tres trimestres de gestación en mujeres sanas suplementadas con yodo y definir los límites de referencia de la normalidad de esta población. Diseño Estudio descriptivo sobre la mujer gestante para definir los límites de normalidad de hormonas tiroideas en esta población. Emplazamiento Jaén y Osuna. Población Gestantes sanas. Métodos Determinación de hormonas tiroideas en los tres trimestres de gestación en mujeres sanas suplementadas con yodo. Resultados Cuatrocientas veintinueve gestantes fueron suplementadas con yodo para mantener nivel de yoduria en los límites de normalidad. Las concentraciones de T4-l estuvieron entre 0,60 y 1,06 para el primer trimestre, entre 0,43 y 0,85 ng/dl en el segundo trimestre y entre 0,40 y 0,82 ng/dl en el tercer trimestre. Para la TSH los valores de referencia son: 0,23 y 4,18μUI/ml en el primer trimestre, 1,78 y 3,89μUI/ml en el segundo trimestre y 2,01 y 4,30μUI/ml en el tercer trimestre. Para T3-l los límites en el primer trimestre es de 2,33 a 3,84 pg/ml, entre 2,04 y 3,51 pg/ml en el segundo trimestre y entre 1,99 y 3,46 pg/ml en el tercer trimestre. ConclusiónLos límites de referencia para nuestra población teniendo en cuenta los percentiles 3 y 97 están muy por debajo del recomendado por nuestro laboratorio de referencia, lo que obliga a redefinir estas concentraciones para evitar diagnosticar de forma incorrecta de hipotiroxinemia a la mujer gestante sana (AU)

Objective: To evaluate thyroid function in the three trimesters of pregnancy in healthy women taking iodine and to define the reference ranges of normality in this population. Design: Descriptive study of pregnant women to define the ranges of normality of thyroid hormones in this population. Setting: Jaen and Osuna (Spain).Population: Healthy pregnant women. Methods: Thyroid hormone determination in the three trimesters of pregnancy in healthy women taking iodine supplements. Results: A total of 429 pregnant women taking iodine supplements to maintain urinary iodine levels within the normal range were included. T4-l levels were between 0.60 and 1.06 in the first trimester, between 0.43 and 0.85 ng/dl in the second and between 0.40 and 0.82 ng/dl in thethird. Thyroid stimulating hormone (TSH) reference values were between 0.23 and 4.18 UI/mlin the first trimester, 1.78 and 3.89 UI/ml in the second and 2.01 and 4.30 UI/ml in the third.T3-l values were between 2.33 and 3.84 pg/ml in the first trimester, between 2.04 and 3.51pg/ml in the second and between 1.99 and 3.46 pg/ml in the third. Conclusion: Bearing the 3rd and 97th percentiles in mind, the reference ranges in our population were far below those recommended by our reference laboratory. In view of these results, these values should be redefined to avoid incorrect diagnoses of hyperthyroxinemia in healthypregnant women (AU)

Thyroid antigens, not central tolerance, control responses to immunization in BALB/c versus C57BL/6 mice.

BACKGROUND: Vaccination with cDNA for the human thyrotropin receptor (TSHR) in a plasmid, without adjuvant, induces TSHR antibodies in C57BL/6 but rarely in BALB/c mice. This outcome could be due to a difference between "high" versus "low" antibody responder mouse strains. However, unlike their poor response to TSHR-DNA vaccination, BALB/c mice vaccinated with thyroid peroxidase (TPO)-cDNA readily develop antibodies to TPO. We hypothesized that insight into these conundrums would be provided by the following differences in central tolerance: (i) between two mouse strains (C57BL/6 versus BALB/c) for the TSHR; and (ii) between two thyroid autoantigens (TPO and the TSHR) in one mouse strain (BALB/c). METHODS: We studied autoantigen expression using real-time polymerase chain reaction to quantify mRNA transcripts for the TSHR, TPO, and thyroglobulin (Tg) in thymic tissue (as well as in thyroid) of young mice. RESULTS: Our hypothesis was not confirmed. Intrathymic TSHR transcript expression was similar in BALB/c and C57BL/6 mice. Moreover, thymic mRNA transcripts for TSHR and TPO were comparable. Unlike the 10-fold differences for the autoantigens in thyroid tissue (Tg greater than TPO which, in turn was greater than the TSHR), intrathymic transcripts for TPO and the TSHR were similar, both being slightly lower than the level for Tg. CONCLUSIONS: Central tolerance, assessed by measuring intrathymic transcripts of thyroid autoantigens, does not explain the different outcome of TSHR-DNA vaccination in BALB/c and C57BL/6 mice, or even susceptibility versus resistance to hyperthyroidism induced by TSHR-adenovirus. Instead, differences in MHC and TSHR T-cell epitopes likely contribute to TSHR antibody development (or not) following DNA plasmid immunization. The greater immunogenicity of TPO versus TSHR probably relates to the greater number of nonhomologous amino acids in the human and mouse TPO ectodomains (78 amino acids) than in the human and mouse TSHR ectodomains (58 amino acids). Overall, the autoantigens themselves, not central tolerance, control DNA plasmid-induced immunity to TPO and the TSHR.

Exacerbation of autoimmune thyroiditis by a single low dose of whole-body irradiation in non-obese diabetic-H2h4 mice.

PURPOSE: To evaluate how irradiation affects thyroid autoimmunity in mouse models of Hashimoto's thyroiditis and Graves' hyperthyroidism. MATERIALS AND METHODS: Non-obese diabetic (NOD)-H2(h4) mice spontaneously develop anti-thyroglobulin (Tg) antibodies and thyroiditis when supplied with sodium iodine (NaI) in the drinking water. BALB/c mice develop anti-thyrotropin receptor (TSHR) antibodies and hyperthyroidism following immunization with adenovirus expressing TSHR (Ad-TSHR). Mice were irradiated as follows: A single whole-body irradiation with 0.05, 0.5 or 3 Gy one week before or after the beginning of NaI or immunization with Ad-TSHR, fractionated whole-body irradiations with 0.05 Gy twice a week or 0.5 Gy once a week from one week before NaI or Ad-TSHR immunization, or a single regional irradiation to the thyroid gland with 0.5 Gy one week before NaI. The effect of a single irradiation with 0.05, 0.5 or 3 Gy on splenocytes was also evaluated. RESULTS: A single whole-body irradiation with 0.5 Gy one week before NaI exacerbated thyroiditis and increased anti-Tg antibody titers in NOD-H2(h4) mice. In contrast, any irradiation protocols employed did not affect incidence of hyperthyroidism or anti-TSHR antibody titers in BALB/c mice. High-dose irradiation increased the relative ratios of effector T cells to regulatory T cells (an indication of enhanced immune status) but kills most of T cells. CONCLUSIONS: These results indicate that a single whole-body low-dose irradiation with 0.5 Gy exacerbates thyroiditis in NOD-H2(h4) mice, data consistent with some clinical evidence for increased incidence of thyroid autoimmunity by environmental irradiation.

Serum selenium levels in patients with remission and relapse of graves' disease.

OBJECTIVE: Selenium (Se) in the form of selenocysteine is an essential component of the family of the detoxifying enzymes glutathione peroxidase (Gpx) and of the iodothyronine selenodeiodinases that catalyze the extrathyroidal production of tri-iodothyronine (T(3)). Thus, Se deficiency may seriously influence the generation of free radicals, the conversion of thyroxine (T(4)) to T(3) and a thyroidal autoimmune process. The aim of this study was to investigate whether serum Se levels may influence the outcome of Graves' disease (GD). DESIGN AND METHODS: 83 patients (77 women, 6 men) with active GD were retrospectively analyzed (mean age 40,0 years). Twenty-four GD patients went into remission and were euthyroid during follow-up (median follow-up: 20.1 months), whereas 59 patients did not go into remission or developed relapse over the following 24 months. TSH receptor autoantibodies (TRAb) were measured using the second generation assay on the basis of human TSH receptor. Se levels were determined at the first visit in our outpatient clinic and were correlated with TRAb levels and clinical outcome of these patients. RESULTS: Median TRAb levels in the group of remission were significantly (p<0.0001) lower than TRAb values in the relapse group (2.1 as compared to 8.6 IU/l). By comparing mean serum Se levels in the remission and relapse group no significant differences were seen (73.0 vs. 71.7 microg/l). Detailed analyses of both groups of patients, however, revealed that highest serum Se levels (>120 microg/l) were seen in the remission group, indicating a positive effect of Se levels on the outcome of GD. In addition, we also compared these results with TRAb levels of these patients. We could show that TRAb levels and serum Se values were positively correlated in the relapse group, whereas a negative correlation of both parameters were seen in the remission group, supporting the idea of a positive effect of Se on thyroidal autoimmune process. CONCLUSION: Our data indicate that high serum Se levels (>120 microg/l) may influence the outcome of GD. This is important, as Se administration trials in GD, which are under discussion need to be performed with Se supplementation at higher dosages than used in autoimmune thyroiditis.

Thyroid hormone state and quality of life at long-term follow-up after randomized treatment of Graves' disease.

OBJECTIVE: In a 14-21 year follow-up of health-related quality of life (HRQL) outcome of 179 patients after randomized treatment of Graves' disease (GD) with surgical, medical or radioiodine, we found no differences. The HRQL for Graves' patients, however, was lower compared with a large age- and sex-matched Swedish reference population. We have now studied whether the reported HRQL-scores by Medical Outcome Study 36-item Short-Form Health Status Survey (SF36) and quality of life 2004 (QoL2004) answers were related to the thyroid hormone state of the patient. METHODS: This report comprises 91 of the original patients in which both the results of SF36 and QoL2004 questionnaire as well as serum thyroid hormones and current use of l-thyroxine treatment were available. RESULTS: A large number of the patients had low or undetectable serum TSH concentrations. SF36 scores and answers to QoL2004 questionnaires were not correlated to TSH levels or associated with suppressed TSH. A low free triiodothyronine was weakly associated with a low GH score (P < 0.02) and elevated thyrotropin receptor antibody with a low physical component summary (P < 0.02). CONCLUSION: HRQL do not seem to be influenced by the thyroid hormone state of the patient including subclinical thyrotoxicosis. It is possible that the personality of GD patients as such may have resulted both in the development of GD and lower HQRL scores later on in life. Alternatively, the generic SF36 may not be a proper instrument to detect relevant differences in HRQL related to the thyroid state.

Does thyrotropin cleave its cognate receptor?

A recent report of major pathophysiological significance, and opposed to present concepts, is that TSH (but not MS-1, a hamster monoclonal thyroid-stimulating antibody), cleaves the single-chain TSH receptor (TSHR) on the cell surface into its two-subunit form. We reassessed the issue using two approaches. First we wished to confirm the flow-cytometric assay previously used to quantitate TSHR cleavage. We used CHO cell lines expressing large (TSHR-10,000 cells) or conventional (TSHR-0 cells) numbers of TSHR. Cells were preincubated (16 h) in either control medium or medium supplemented with TSH (5 x 10(-8) m) or MS-1 (10 microg/ml). After stringent washing to maximize removal of residual ligand, we performed flow cytometry with two antibodies, one recognizing only the single-chain TSHR, the other recognizing all (cleaved and uncleaved) TSHRs. TSH pretreatment did not appear to increase TSHR cleavage. Instead we observed ligand occupancy of the TSHR (with MS-1) or fewer receptors on the cell surface (down-regulation), particularly with the TSHR-0 cells. Second, we covalently cross-linked [125I]TSH to monolayers of these cells, an unequivocal method to determine directly the proportion of single-chain and two-subunit TSHR forms. Pretreatment of TSHR-10,000 and TSHR-0 cells with TSH had no effect on the degree of TSHR cleavage. MS-1 slightly reduced spontaneous cleavage. In conclusion, in contrast to a recent report, we show that TSH does not alter the subunit structure of its cognate receptor, and we provide insight into the difficulties associated with the flow-cytometric assay for TSHR cleavage.

The cysteine-rich amino terminus of the thyrotropin receptor is the immunodominant linear antibody epitope in mice immunized using naked deoxyribonucleic acid or adenovirus vectors.

Experimental Graves' disease is more effectively produced by immunization approaches involving in vivo TSH receptor (TSHR) expression than by conventional immunization with TSHR protein and adjuvant. Unlike conformational epitopes that are extremely difficult to define, linear epitopes can be readily assessed using synthetic peptides. TSHR linear epitopes are well characterized in conventionally immunized animals, but there is no information for animals vaccinated with TSHR DNA in plasmid or adenovirus vectors. We used synthetic peptides to characterize linear epitopes in mice immunized by in vivo expression of TSHR DNA. TSHR adenovirus-injected mice had higher antibody levels than TSHR DNA-vaccinated mice. However, the dominant peptide recognized in both groups was the TSHR cysteine-rich N terminus (residues 22-41). Sera from TSHR adenovirus-immunized (but not TSHR DNA-vaccinated) mice interacted to a lesser extent with peptides encompassing residues 352-401, which include the region deleted following TSHR cleavage as well as the ectodomain juxta-membrane region. Although antibodies characterized using synthetic peptides are probably TSH blockers or nonfunctional, stimulating antibodies may recognize linear components in a conformational epitope. The cysteine-rich TSHR N terminus is functionally important in the action of stimulating TSHR autoantibodies in humans. The immunodominance of the same region in immunized mice suggests that this region may also be immunodominant in humans.

Regulation and transfer of a murine model of thyrotropin receptor antibody mediated Graves' disease.

In order to replicate a recently described murine model of Graves' disease, we immunized AKR/N (H-2k) mice i.p., every 2 weeks, with either a clone of fibroblasts expressing both the human TSH receptor (hTSHR) and murine major histocompatibility complex (MHC) class II molecules or with fibroblasts expressing the MHC class II molecules alone. Mice were bled, and their thyroid hormone levels measured, at 6, 12, and up to 18 weeks after the first immunization. Between 11-12 weeks after immunization, a significant number of mice began to die spontaneously and were found to have developed large goiters. Thirty to 40% of mice immunized with hTSHR transfected fibroblasts showed markedly increased serum T3 and T4 hormone levels by 12 weeks compared with controls, with the highest thyroid hormone levels being T3: 420 ng/dl (normal < 70) and T4: 16.5 microg/dl (normal < 5). The murine serum demonstrated the presence of antibodies to the TSHR, as evidenced by inhibition of labeled TSH binding to the hTSHR, and these sera had in vitro thyroid stimulating activity. Many of the hyperthyroid mouse exhibited weight loss and hyperactivity and, on examination, their thyroids had the histological features of thyroid hyperactivity including thyroid enlargement, thyroid cell hypertrophy, and colloid droplet formation--all consistent with Graves' disease. In contrast, a small number of mice (< 5%) developed hypothyroidism with low serum T4 levels and markedly increased TSH concentrations and evidence of thyroid hypoplasia. Both hyperthyroidism and hypothyroidism were successfully transferred to naive mice using ip cells of immunized mice. Surprisingly, hypothyroidism occurred in many recipient mice even after transfer from hyperthyroid donors. These results confirmed that immunization with naturally expressed hTSHR in mammalian cells was able to induce functional TSHR autoantibodies that either stimulated or blocked the mouse thyroid gland and induced hyperthyroidism or thyroid failure. Furthermore, both blocking and stimulating antibodies coexisted in the same mice as evidenced so clearly by the transfer of hypothyroidism from hyperthyroid mice. The addition of a Th2 adjuvant (pertussis toxin) caused approximately 50% of the animals to become hyperthyroid beginning early at 9 weeks, whereas a Th1 adjuvant (CFA) delayed the disease onset such that only 10% were hyperthyroid by 12 weeks. As with human autoimmune thyroid disease, the T cell control of this murine model may be critical and requires more extensive investigation.

Elimination kinetics of maternally derived thyrotropin receptor-blocking antibodies in a newborn with significant thyrotropin elevation.

OBJECTIVE: To determine the course of maternally derived elevations in thyrotropin-binding inhibitory immunoglobulins in a neonate. DESIGN: Case report. SETTING: University pediatric endocrinology clinic and endocrine immunology laboratory in Ohio. PARTICIPANTS: An infant with elevated thyrotropin levels but near-normal total thyroxine levels, and her mother. INTERVENTIONS: None. MEASUREMENTS/MAIN RESULTS: Thyroid hormone, thyrotropin, and thyrotropin-blocking immunoglobulin concentrations were serially measured in a woman and her infant, who was found to have elevated thyrotropin levels (234 mU/L) and borderline low thyroxine levels (95 nmol/L). As infant thyroxine concentrations remained normal (125 to 145 nmol/L), no thyroxine supplementation was given. Thyrotropin levels decreased concomitantly with thyrotropin-blocking inhibitory immunoglobulin levels, and normalized by day 56 of life. The apparent elimination half-life of thyrotropin-blocking immunoglobulins was 7.5 days. CONCLUSIONS: The observed parallel elimination kinetics suggest that the thyrotropin receptor antibody acts as a thyrotropin antagonist, resulting in compensatory thyrotropin elevations. The duration of such elevations may be predicted on the basis of such elimination.