Effects of radioiodine on thyrotrophin binding inhibiting immunoglobulins in Graves' disease

A transgenic mouse that spontaneously develops pathogenic TSH receptor antibodies will facilitate study of antigen-specific immunotherapy for human Graves' disease

Graves' hyperthyroidism can be treated but not cured. Antigen-specific immunotherapy would accomplish this goal, for which purpose an animal model is an invaluable tool. Two types of animal models are available. First, pathogenic TSHR antibodies (TSHRAb) can be induced by injecting mice with fibroblasts co-expressing the human TSHR (hTSHR) and MHC class II, or in mammals using plasmid or adenovirus vectors encoding the hTSHR or its A-subunit. Second, a mouse model that spontaneously develops pathogenic TSHRAb resembling those in human disease was recently described. This outcome was accomplished by transgenic intrathyroidal expression of the hTSHR A-subunit in NOD.H2^h4 mice that are genetically predisposed to develop thyroiditis but, without the transgene, do not generate TSHRAb. Recently, novel approaches to antigen-specific immunotherapy have been tested, primarily in the induced model, by injecting TSHR A-subunit protein or cyclic TSHR peptides. T-cell tolerance has also been induced in "humanized" HLA-DR3 mice by injecting synthetic peptides predicted in silico to mimic naturally processed TSHR T-cell epitopes. Indeed, a phase 1 study based on the latter approach has been conducted in humans. In the spontaneous model (hTSHR/NOD.H2^h mice), injection of soluble or nanoparticle-bearing hTSHR A-subunits had the unwanted effect of exacerbating pathogenic TSHRAb levels. A promising avenue for tolerance induction, successful in other conditions and yet to be tested with the TSHR, involves encapsulating the antigen. In conclusion, these studies provide insight into the potential outcome of immunotherapeutic approaches and emphasize the importance of a spontaneous model to test future novel, antigen-specific immunotherapies for Graves' disease.

Nanoparticles Bearing TSH Receptor Protein and a Tolerogenic Molecule Do Not Induce Immune Tolerance but Exacerbate Thyroid Autoimmunity in hTSHR/NOD.H2h4 Mice

Transgenic NOD.H2^h4 mice that express the human (h) TSHR A-subunit in the thyroid gland spontaneously develop pathogenic TSHR autoantibodies resembling those in patients with Graves disease. Nanoparticles coupled to recombinant hTSHR A-subunit protein and a tolerogenic molecule (ligand for the endogenous aryl-hydrocarbon receptor; ITE) were injected i.p. four times at weekly intervals into hTSHR/NOD.H2^h4 mice with the goal of blocking TSHR Ab development. Unexpectedly, in transgenic mice, injecting TSHR A-subunit-ITE nanoparticles (not ITE-nanoparticles or buffer) accelerated and enhanced the development of pathogenic TSHR Abs measured by inhibition of TSH binding to the TSHR. Nonpathogenic TSHR Abs (ELISA) were enhanced in transgenics and induced in wild-type littermates. Serendipitously, these findings have important implications for disease pathogenesis: development of Graves TSHR Abs is limited by the availability of A-subunit protein, which is shed from membrane bound TSHR, expressed at low levels in the thyroid. The enhanced TSHR Ab response following injected TSHR A-subunit protein-nanoparticles is reminiscent of the transient increase in pathogenic TSHR Abs following the release of thyroid autoantigens after radio-iodine therapy in Graves patients. However, in the hTSHR/NOD.H2^h4 model, enhancement is specific for TSHR Abs, with Abs to thyroglobulin and thyroid peroxidase remaining unchanged. In conclusion, despite the inclusion of a tolerogenic molecule, injected nanoparticles coated with TSHR A-subunit protein enhanced and accelerated development of pathogenic TSHR Abs in hTSHR/NOD. NOD.H2^h4 These findings emphasize the need for sufficient TSHR A-subunit protein to activate the immune system and the generation of stimulatory TSHR Abs in genetically predisposed individuals.

Breaking tolerance to thyroid antigens: changing concepts in thyroid autoimmunity

Thyroid autoimmunity involves loss of tolerance to thyroid proteins in genetically susceptible individuals in association with environmental factors. In central tolerance, intrathymic autoantigen presentation deletes immature T cells with high affinity for autoantigen-derived peptides. Regulatory T cells provide an alternative mechanism to silence autoimmune T cells in the periphery. The TSH receptor (TSHR), thyroid peroxidase (TPO), and thyroglobulin (Tg) have unusual properties ("immunogenicity") that contribute to breaking tolerance, including size, abundance, membrane association, glycosylation, and polymorphisms. Insight into loss of tolerance to thyroid proteins comes from spontaneous and induced animal models: 1) intrathymic expression controls self-tolerance to the TSHR, not TPO or Tg; 2) regulatory T cells are not involved in TSHR self-tolerance and instead control the balance between Graves' disease and thyroiditis; 3) breaking TSHR tolerance involves contributions from major histocompatibility complex molecules (humans and induced mouse models), TSHR polymorphism(s) (humans), and alternative splicing (mice); 4) loss of tolerance to Tg before TPO indicates that greater Tg immunogenicity vs TPO dominates central tolerance expectations; 5) tolerance is induced by thyroid autoantigen administration before autoimmunity is established; 6) interferon-α therapy for hepatitis C infection enhances thyroid autoimmunity in patients with intact immunity; Graves' disease developing after T-cell depletion reflects reconstitution autoimmunity; and 7) most environmental factors (including excess iodine) "reveal," but do not induce, thyroid autoimmunity. Micro-organisms likely exert their effects via bystander stimulation. Finally, no single mechanism explains the loss of tolerance to thyroid proteins. The goal of inducing self-tolerance to prevent autoimmune thyroid disease will require accurate prediction of at-risk individuals together with an antigen-specific, not blanket, therapeutic approach.

Radioiodine therapy in benign thyroid diseases: effects, side effects, and factors affecting therapeutic outcome

Radioiodine ((131)I) therapy of benign thyroid diseases was introduced 70 yr ago, and the patients treated since then are probably numbered in the millions. Fifty to 90% of hyperthyroid patients are cured within 1 yr after (131)I therapy. With longer follow-up, permanent hypothyroidism seems inevitable in Graves' disease, whereas this risk is much lower when treating toxic nodular goiter. The side effect causing most concern is the potential induction of ophthalmopathy in predisposed individuals. The response to (131)I therapy is to some extent related to the radiation dose. However, calculation of an exact thyroid dose is error-prone due to imprecise measurement of the (131)I biokinetics, and the importance of internal dosimetric factors, such as the thyroid follicle size, is probably underestimated. Besides these obstacles, several potential confounders interfere with the efficacy of (131)I therapy, and they may even interact mutually and counteract each other. Numerous studies have evaluated the effect of (131)I therapy, but results have been conflicting due to differences in design, sample size, patient selection, and dose calculation. It seems clear that no single factor reliably predicts the outcome from (131)I therapy. The individual radiosensitivity, still poorly defined and impossible to quantify, may be a major determinant of the outcome from (131)I therapy. Above all, the impact of (131)I therapy relies on the iodine-concentrating ability of the thyroid gland. The thyroid (131)I uptake (or retention) can be stimulated in several ways, including dietary iodine restriction and use of lithium. In particular, recombinant human thyrotropin has gained interest because this compound significantly amplifies the effect of (131)I therapy in patients with nontoxic nodular goiter.

Graves' ophthalmopathy: a review of immunogenetics

Graves’ disease (GD) is the most common cause of thyrotoxicosis and often involves the orbits. Graves’ ophthalmopathy (GO), also known as Thyroid Eye Disease (TED), can be clinically significant and advance to sight-threatening stages. Our knowledge of the immunogenetic pathophysiology of GO is rapidly expanding. The present review is an attempt to summarize the current state of knowledge on the immunogenetics of GO. First we briefly review the epidemiology and clinical importance of GO, and then we describe in detail the macromolecular pathogenesis and finally immunogenetics of GO. Discrepancies between the results from various reports and the limitations of the available data are discussed. In particular, there is a scarcity of data from non-Asian populations. While several studies have demonstrated significant associations between polymorphisms in certain genes (especially CTLA-4, HLA-DRB-1, and TNF-α), there is a need for studies that investigate the relationship between polymorphisms and both serum and local concentrations of the resulting proteins. A complete understanding of GO susceptibility and pathogenesis has not been yet possible due to a number of important knowledge gaps that need to be filled by future research.

Immunotherapy in miscellaneous medical disorders Graves ophthalmopathy, asthma, and regional painful syndrome

In Graves ophthalmopathy, immunotherapy is offering an opportunity of reducing bad outcomes that lead to disfigurement and impairment of vision. These therapies are not perfect; however, we now have a chance to achieve better outcomes. In asthma, immune therapy using passive immunity targeting key proinflammatory cytokine/chemokines and medications of their effects has opened an avenue of research into a safe and durable therapy. Omalizumab appears to be safe and effective in clinical use. In regional pain syndrome, immune mechanisms may be involved in sustaining long-standing pain, and IVIG may moderate pain sensitivity by reducing immune activation.

Precocious hypothyroidism mechanisms after radioiodine treatment in Graves' disease

OBJECTIVE

Hypothyroidism can occur after radioiodine treatment for Graves' disease. It may happen precociously and transiently in the first year after treatment. The purpose of this study was to understand the mechanisms responsible for precocious hypothyroidism.

METHODS

36 patients treated for Graves disease by radiodiodine were prospectively studied; The following variables were included in the analysis: age, gender, attendance for Graves' orbitopathy (GO), delay before radioiodine treatment, number of recurrences, previous treatments, corticosteroid therapy, thyroid mass, and (131)I dose. The titres of free T4 (FT4), thyroid-stimulating hormone (TSH), anti-TSH receptor antibodies (TRAb), anti-thyroid peroxydase antibodies (TPOAb) and anti-thyroglobulin antibodies (TGAb) were monitored. Thyroid stimulating (TSAb) and blocking (TBAb) antibodies were determined and (123)I uptake was measured when hypothyroidism occurred.

RESULTS

23 patients became precociously hypothyroid (group A) while 13 patients did not (group B). The initial TGAb titre was higher in group A (p=0.0024), and corticosteroid therapy was used more frequently to avoid aggravating GO in group B (p=0.0276). TPOAb and TGAb titres increased significantly only in group A (p=0.0112 and p=0.0202, respectively). When hypothyroidism occurred, TBAb was present in 13 patients. Transient hypothyroidism due to TBAb was observed in 1 patient. No iodide organification impairment was disclosed by the perchlorate test.

CONCLUSION

Radioinduced thyroiditis appears to be the main mechanism involved in the pathogenesis of precocious hypothyroidism. A higher TGAb titre before treatment is associated with precocious hypothyroidism, suggesting the prognostic value of TGAb. Transient hypothyroidism directly due to TBAb remains rare.

Update Thyroid-Associated Ophthalmopathy

Thyroid-associated ophthalmopathy (TAO) is one of the most vexing problems in endocrinology but its relationship to thyroid autoimmunity is becoming more clear with the realisation that almost all patients with Graves' disease have this condition and almost all patients with ophthalmopathy have some form of thyroid involvement. This suggests cross reactivity between thyroid and retrobulbar antigens, of which one potential candidate has recently been cloned. Together with new information on predisposing factors and the important role of the retrobulbar fibroblasts, these developments shed new light on the aetiology and pathogenesis of this enigmatic disorder.

Radiotherapy-associated Euthyroid Graves Ophthalmopathy following Floor-of-mouth Surgery: A Case Report

The thyroid gland is commonly included in the radiation field during treatment of nonthyroidal neoplastic disease of the head and neck. As a result, thyroid abnormalities sometimes occur following external irradiation. We report an unusual case of radiotherapy-associated Graves ophthalmopathy 5 months after adjuvant external irradiation of the head and neck in a euthyroid patient who had undergone wide local excision of squamous cell carcinoma from the floor of the mouth.

Thyroidectomy remains an effective treatment option for Graves’ disease

BACKGROUND

Recent experience with thyroidectomy for Graves' disease is limited. We report our current experience with thyroidectomy for Graves' disease at a tertiary hospital.

METHODS

A prospective database showed 48 patients who underwent surgery for Graves' disease from April 1993 to June 2005.

RESULTS

All patients had typical symptoms of Graves' disease. Twenty-three patients had ophthalmopathy. Indications for surgery were failed medical therapy (n = 24), presence of a dominant nodule (n = 12), or refusal of radioiodine (n = 12). Surgery included total thyroidectomy (n = 46) or subtotal thyroidectomy (n = 2). The incidence of cancer was 17%. Long-term follow-up data were available for 44 patients. No patients had recurrence of hyperthyroidism or cancer. Follow-up evaluation of 20 patients with ophthalmopathy showed the condition had either stabilized or resolved.

CONCLUSIONS

Total thyroidectomy for Graves' disease offers rapid and durable control of hyperthyroidism, provides appropriate treatment for patients with coexisting cancer, and can stabilize or reverse ophthalmopathy.

Stimulation of thyroid-stimulating hormone (TSH) receptor antibody production following painless thyroiditis

OBJECTIVE

Development or recurrence of Graves' disease (GD) following painless thyroiditis (PT) has been documented. Therefore, we measured titres of TSH receptor antibodies (TSHR Ab) using a novel sensitive TSHR Ab assay in patients with PT to determine whether PT enhances TSHR Ab production, possibly triggering the development or recurrence of GD.

DESIGN AND MEASUREMENTS

Ninety-two patients who developed PT were studied. Group G consisted of 40 patients with a history of GD (19 patients in remission, 21 who had stopped taking antithyroid drugs during pregnancy). Group P consisted of 52 patients with no history of GD. Serum thyroid hormone levels, thyroid autoantibodies including TSHR Ab, and 123I uptake at 24 h (RAIU) were measured in these patients at the time of PT onset. TSHR Abs were measured by radioreceptor assay using porcine TSH receptors (pTBII) or human TSH receptors (hTBII).

RESULTS

There were no significant differences in serum thyroid hormone levels or pTBII values between groups G and P. Nor was there any significant difference between p- and h-TBII values in group P. There was also no significant difference in pTBII levels before, compared to at the time of PT onset in group G patients. However, hTBII values at the PT onset were significantly higher in the group G than in the group P (7.7 +/- 9.8%vs. 1.4 +/- 5.4%, P = 0.0014). The rate of hTBII positivity was also significantly higher in group G than in group P (12/40 vs. 3/52, P = 0.002). Furthermore, the RAIU in group G patients was significantly higher than that in group P patients (2.8 +/- 2.4%vs. 1.3 +/- 0.9%, P = 0.0002). GD recurrence was observed in seven patients in group G, whose hTBII levels were significantly higher than those of other patients in this group (17.0 +/- 11.8%vs. 5.7 +/- 8.2%, P = 0.02). Of these seven with relapses, five had hTBII values exceeding 15%.

CONCLUSIONS

TBII elevation at the onset of PT in patients with a history of GD was detected by a sensitive hTBII assay. Destruction of the thyroid by PT may trigger GD recurrence in patients with a history of GD.

Levels of soluble human leukocyte antigen class 1 are increased in Graves' disease and toxic multinodular goiter and correlate with the levels of triiodothyronine

Soluble human leukocyte antigens class 1 (sHLA-1) are postulated to play a role in immunomodulation. Thyroid hormones and thyroid stimulating hormone influence expression of major histocompatibility complex (MHC) class 1 genes. We hypothesized similar changes in sHLA-1 with changes in the thyroid hormone. We measured serum levels of sHLA-1 in 140 normal controls, 11 patients with toxic multinodular goiter and 26 patients with active Graves' disease. On follow-up 1 year after treatment for Graves' disease, we repeated the measurement of the levels of sHLA-1 in 21 patients. Levels of sHLA-1 were markedly elevated in the group of patients with active Graves' disease compared to the normal controls (p = 0.00016). The levels of sHLA-1 were also elevated significantly in patients with toxic multinodular goiter compared to normal controls (p = 0.034). There is no significant difference between genders and the two races tested among patients with Graves' disease in contrast to controls. Free triiodothyronine (T(3)) levels positively correlated with the levels of sHLA-1 (r = 0.61). On follow-up after treatment for Graves' disease, levels of sHLA-1 decreased by 62% with p = 0.0006 (active Graves vs. follow-up). We conclude that there is a definite association between thyroid hormones and sHLA-1 levels.

Appearance of anti TSH-receptor antibodies and clinical Graves' disease after radioiodine therapy for hyperfunctioning thyroid adenoma

Radioiodine treatment use is frequent in patients with benign hyperfunctioning thyroid diseases and the side-effects are rare. In this paper we described the appearance of TSH-receptor antibodies and the concomitant development of persistent hyperthyroidism in a patient with hyperfunctioning thyroid adenoma after 131I treatment. A 70-year-old man presented a hyperfunctioning thyroid adenoma with suppressed uptake in the adjacent normal gland. Antibodies against the thyroglobulin (TgAb), thyroid peroxidase (TPOAb) and TSH-receptor (TRAb) were absent. One year after remission by radioiodine therapy the patient developed severe and persistent hyperthyroidism associated with diffuse 131I uptake in the gland. TgAb and TPOAb remained absent, but TRAb were present. Although spontaneous development of Graves' disease cannot be excluded, the time sequence and the negative familial and personal history for autoimmune diseases suggest a possible connection between the two phenomena. The release of TSH-receptor antigen from follicular cells damaged by 131I may have triggered the autoimmune response turning a toxic nodular goiter patient into a Graves' disease patient.

TSH receptor antibody-associated thyroid dysfunction following subacute thyroiditis

OBJECTIVE

Autoimmunity plays an important role in the development of thyrotrophin (TSH) receptor antibodies and the pathogenesis of Graves' disease and Hashimoto's thyroiditis. On the other hand, subacute thyroiditis is a self-limited inflammatory disease of presumed viral aetiology. The aim of this study was to examine whether subacute thyroiditis triggers TSH receptor antibody-associated thyroid disorders.

PATIENTS

We reviewed 1,697 patients with subacute thyroiditis seen between 1985 and 1995.

DESIGN AND MEASUREMENTS

We measured antibodies which inhibit the TSH binding to the TSH receptor (TBIAb), thyroid stimulating antibodies (TSAb) and antibodies that block TSH action (TBAb). Other thyroid autoantibodies were also determined.

RESULTS

TBIAb became positive in 38 patients following subacute thyroiditis. Thyroid function after the development of TBIAb appeared to be influenced by the bioactivity of the antibody. Hyperthyroidism developed in the presence of TSAb, and so did hypothyroidism in the presence of TBAb, although 21 patients did not have thyroid dysfunction despite high titres of TBIAb. Fifteen out of 17 patients recovered from hyperthyroidism or hypothyroidism after the disappearance of TBIAb sometimes even without medication. TBIAb-positive patients had a high incidence of a family history of thyroid disease and positive anti-thyroid microsomal antibodies. An ophthalmopathy similar to Graves' disease was also observed in 3 patients.

CONCLUSIONS

Subacute thyroiditis may trigger autoreactive B cells to produce TSH receptor antibodies, resulting in TSH receptor antibody-associated thyroid dysfunction in some patients.

Role of thyroid-stimulating blocking antibody in patients who developed hypothyroidism within one year after 131I treatment for Graves' disease

OBJECTIVE

We recently reported that thyroid-stimulating blocking antibody (TSBAb) may not contribute to the development of hypothyroidism more than six years after 131I treatment. In the present study, we attempted to determine whether hypothyroidism that develops within a shorter period of time following 131I therapy is associated with TSBAb.

DESIGN

Retrospective study.

PATIENTS

Sera were obtained from 8 patients who developed hypothyroidism within 6 months after 131I therapy (Group 1), 8 patients who became euthyroid one year after 131I therapy (Group 2), and 7 patients who developed transient hypothyroidism (Group 3).

MEASUREMENTS

Thyroid stimulating antibody (TSAb) activity was measured as the amount of cyclic adenosine monophosphate (cAMP) produced by cultured FRTL-5 cells, and TSBAb activity as the inhibition of cAMP produced in response to 100 mU/l bovine TSH.

RESULTS

At about 3 months after 131I treatment, TSAb activity increased significantly in Groups 2 and 3, but did not change in Group 1. In contrast, TSBAb activity in Group 1 increased significantly and was positive in 6 patients at that time. At 12-18 months after 131I treatment, TSBAb activity tended to decrease and remained positive in 3 patients but became negative in 3 patients. It did not change in the patients in Groups 2 and 3. The patients in Group 1 were treated with levothyroxine, 75-125 micrograms/day. Levothyroxine was discontinued in the 3 patients whose TSBAb activity disappeared. Two of them remained euthyroid, and 1 became hypothyroid.

CONCLUSION

Results indicate that the hypothyroidism that develops within a short time after 131I treatment may be caused by TSBAb activity. Thyroid function may be recovered when TSBAb activity disappears.

Autoimmune hyperthyroidism occurring late after radioiodine treatment for volume reduction of large multinodular goiters

131I treatment is an effective alternative to surgery in patients with a large, (non-)toxic, compressive goiter. Late development of hyperthyroidism after 131I therapy for nontoxic nodular goiter is considered rare. We have seen this complication in 3 of approximately 80 patients treated with radioiodine for volume reduction of a large, multinodular goiter. Three women, aged 60 to 71 years, had large, multinodular goiters causing tracheal compression. They were clinically euthyroid before 131I therapy and had normal free thyroxine (FT4) levels. Serum thyroid-stimulating hormone (TSH) levels were normal in 2 patients and undetectable in 1 patient. Patients 1 and 2 received a single dose of 86 and 48 mCi 131I, respectively. Patient 3 received 20 mCi 131I twice (interval 1 month). Clinical and biochemical thyrotoxicosis with high thyroid radioactive iodide uptake (RAIU) developed 10, 6, and 3 months after 131I therapy, respectively, although at control visits 1 to 3 months earlier, serum TSH and FT4 levels were normal. Thyrotoxicosis responded well to methimazole in all three patients. The late occurrence of thyrotoxicosis, high RAIU, and good response to methimazole argue against thyroiditis as the cause of thyrotoxicosis. Serum levels of TSH receptor antibodies, which were undetectable before therapy (patients 1 and 2), were clearly elevated in all three patients during thyrotoxicosis. This is in favor of autoimmune hyperthyroidism as the cause of thyrotoxicosis. These cases illustrate that severe autoimmune hyperthyroidism may occur several months after radioiodine treatment for nontoxic, multinodular goiter. Information about symptoms of hyperthyroidism and regular control visits in the first year after therapy are important in these patients.

Relationship between thyroid-stimulating antibodies and thyrotropin-binding inhibitory immunoglobulins years after administration of radioiodine for Graves' disease: retrospective clinical survey

Thyroid-stimulating antibody (TSAb) activity and the TSH-binding inhibitory immunoglobulin (TBII) index were assessed in 158 patients with Graves' disease who had been treated with 131I 6-14 years earlier. Twenty-one patients (13%) were still hyperthyroid, 45 (28%) were euthyroid, 44 (28%) were subclinically hypothyroid, and 48 (30%) were overtly hypothyroid. Positive results were obtained in 10 (48%) of the 21 patients with hyperthyroidism for both TSAb and TBII assays, and in 3 patients (14%) in one of the assays. In contrast, only two (5%) patients with subclinical hypothyroidism and 1 (2%) patient with overt hypothyroidism tested positive in both assays, and 11 (25%) subclinically hypothyroid patients and 15 (31%) overtly hypothyroid patients tested positive in one of the assays. The correlation coefficients between TSAb and TBII were 0.88 (p < 0.01) in hyperthyroid patients, 0.49 (p < 0.01) in euthyroid patients, 0.34 (p < 0.05) in subclinically hypothyroid patients, and 0.12 (p > 0.05) in patients with overt hypothyroidism. Findings indicate the presence of long-term changes in the population of TSH receptor antibodies years after 131I treatment, which may influence thyroid function.

Specific effects of radioiodine treatment on TSAb and TBAb levels in patients with Graves' disease

Radioactive iodine (RAI)-induced changes in the levels of antibodies to the thyroid-stimulating hormone (TSH) receptor (TRAb) in patients undergoing treatment for autoimmune thyroid disease have been well documented. Previous studies have reported effects on the overall level of the antibodies present, TSH-binding inhibitory immunoglobulins (TBII), without detailed studies of specific effects on the levels of thyroid-stimulating (TSAb) or thyroid-blocking antibodies (TBAb). More detailed studies have been reported only in individual cases. In this study, the values of TSAb, TBAb, and TBII were measured longitudinally in 33 patients (27 females and 6 males) who received RAI. The bioassays for TSAb and TBAb were performed in JPO9 cells. Following RAI, there were significant and immediate effects on the values of TBII in 70% of patients. TBII levels fell in 7 patients (20%) (Group 1), rose in 16 patients (48%) (Group 2) or remained unchanged but elevated in 10 patients (32%) (Group 3). In the Group 1 patients, only TSAb were detectable and none of these patients became hypothyroid after treatment. In the 16 patients in Group 2, increases in TBII were attributable to specific increases in TSAb in 7 (44%), in TBAb in 3 (19%), and in both TSAb and TBAb in 3 (19%). There were 3 patients (19%) in this group in whom there was no detectable TSAb or TBAb activity despite the increase in TBII. Six patients from this group became hypothyroid within 6 months of RAI treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term effects of radioiodine on thyrotrophin receptor antibodies in Graves' disease

OBJECTIVE

Graves' disease is recognized as an organ-specific autoimmune disorder caused by the presence of TSH receptor antibodies. The long-term effects of 131I treatment for Graves' disease on TSH receptor antibodies have not previously been studied. We have measured the TSH-binding inhibitory immunoglobulin (TBII) index and thyroid stimulating antibody (TSAb) activity in patients with Graves' disease following treatment with 131I.

DESIGN

A retrospective study.

PATIENTS

Two hundred and twenty-five patients with Graves' disease who were treated with 131I 1-13 years earlier were studied (1 year: 27 patients; 2-5 years: 42 patients; 6-9 years: 79 patients; 10-13 years: 77 patients).

MEASUREMENTS

The TBII index was measured as the percentage 125I-TSH bound to pig thyroid membranes and TSAb activity as the amount of cAMP produced by cultured FRTL-5 cells.

RESULTS

TBII was detected in 78% of patients prior to 131I administration. Following 131I administration, the incidence of positive TBII was 85% at the end of the first year decreasing to 40, 19, and 17% at 2-5, 6-9 and 10-13 years, respectively. The frequency of a positive TSAb was 74% at the end of the first year, and also decreased to 49, 27 and 29% at 2-5, 6-9 and 10-13 years, respectively. At more than 2 years after 131I therapy, the frequencies of hyperthyroidism in TBII and TSAb positive patients were 42% (19/45) and 30% (19/63), respectively, which were significantly higher than those in TBII and TSAb negative patients (8%: 12/153 and 8%:11/131, respectively). The frequency of hyperthyroidism after 131I treatment in patients with negative TBII before treatment (7%:2/29) was significantly lower than that (29%:30/102) in patients with positive TBII before treatment.

CONCLUSIONS

These results indicate that (1) the TBII index and TSAb activity decreased over a period of more than 2 years after 131I therapy for Graves' disease, and (2) the TBII index before treatment may influence the long-term outcome of 131I therapy.

Has the use of antithyroid drugs for Graves' disease become obsolete?

In spite of an experience of almost 50 years of use of antithyroid drugs and radioiodine for the treatment of Graves' disease, the rationale for choice is often obscure. Early reports of high remission rates during thiourea therapy were followed by less optimistic ones, which along with other factors may have fueled the current major shift toward use of radioiodine. This review examines whether or not the use of antithyroid drugs indeed may have become obsolete. The intrathyroidal and extrathyroidal mechanisms of action of the drugs are reviewed with emphasis on their potential immunosuppressive effects. The latter may involve a direct effect on thyroid follicular cells, a direct suppression of TSH receptor antibody formation, or indirect effects mediated via heat shock proteins, oxygen free radicals, and the immune system. Potential factors associated with success or failure with antithyroid drug therapy are discussed, such as the effects of dose and duration of treatment, iodine milieu, and concomitant L-thyroxine therapy. The risks inherent to radioiodine therapy are only briefly described with emphasis on the possible aggravation by radioiodine of preexistent ophthalmopathy. The reader must decide whether the evidence marshalled convincingly indicates that the use of the thiourea compounds should be abandoned. The author thinks not, and is optimistic that imminent discovery of the yet elusive and enigmatic pathogenesis of Graves' disease will permit new and innovative treatment or more effective use of currently available therapies.

Clinical course and thyroid stimulating hormone (TSH) receptor antibodies during surgical treatment of Graves' disease

This study assessed the results of surgical treatment for Graves' disease in our hospital and examined the relationship between the values of thyroid stimulating hormone (TSH) receptor antibodies and postoperative thyroid function. From 1983 to 1988, subtotal thyroidectomy was performed in 313 patients with Graves' disease. The follow-up rate was 89.1% (278 of 313 patients). Thirteen (4.2%) patients required methimazole postoperatively for hyperthyroidism and 23 (7.3%) patients required L-thyroxine postoperatively for hypothyroidism. The relationship between the postoperative thyroid function and TSH receptor antibodies was examined. The pre-operative thyrotropin binding inhibitory immunoglobulin (TBII) value had no relationship to postoperative thyroid function. Only in the patients who were hyperthyroid postoperatively did the TBII value remain elevated, but the value decreased gradually in patients who were not hyperthyroid postoperatively. In 43 of 94 patients whose pre-operative TBII values were high, the postoperative TBII value normalized. The higher the preoperative TBII value, the longer time was required for it to normalize postoperatively. The postoperative thyroid stimulating antibody (TSAb) values were higher in patients who remained hyperthyroid than in the patients who were not hyperthyroid. In the patients who remained hyperthyroid postoperatively, there was a significant correlation between the postoperative TBII value and the TSAB value. In the patients who were hypothyroid postoperatively, the TSBAb values were negative. In patients undergoing surgical treatment of Graves' disease, the postoperative TBII and TSAb values were related to postoperative hyperthyroidism. The TSBAb value had no relationship to postoperative hypothyroidism.

Thyrotropin receptor antibodies: advances and importance of detection techniques in thyroid diseases

The study of autoimmune thyroid disorders (AITD) has greatly contributed to our knowledge of autoimmunity. Graves' disease and Hashimoto's thyroiditis represent two ends of the range of autoimmune responses seen in AITD. Autoantibodies reactive to cytoplasmic antigens are associated with cell damage, and thyrotropin (TSH)-receptor antibodies (TRAb) influence the function and growth of the gland and play a major role in pathogenesis. The heterogeneous nature of TRAb is well accepted. Besides their long-known thyroid stimulating activity, TRAb can act as blocking antibodies or growth-promoting antibodies and, thus, cause hypothyroidism (primary myxedema) or endemic and sporadic goiters, respectively. Advanced methodologies for detection of these antibodies with the TSH-receptor assay and thyroid cell bioassay allow various activities to be measured. Current data using these assays confirm the presence of heterogeneity of functional activities of TRAb(s) in vivo. The activity of predominating antibody may relate to clinical presentation. This indicates a need for paired determinations of both TSH-binding inhibitory immunoglobulin (TBII) and thyroid-stimulating immunoglobulin (TSI) for accurate clinical correlations. Cloning the TSH-receptor gene has clarified its structure and function. The future identification of its epitopes will further delineate the clinical role of these antibodies and may allow development of new diagnostic and therapeutic approaches.

Thyroxine replacement in post-radioiodine hypothyroidism

Thyroxine replacement dose in 70 patients with post-radioiodine (for Graves' thyrotoxicosis) hypothyroidism was compared with that in 34 patients with autoimmune hypothyroidism matched for age and sex and diagnosed during the same period. Median replacement dose in the post-radioiodine group (100 micrograms daily) was significantly lower (P = 0.006) than in the autoimmune hypothyroid group (137.5 micrograms daily). Furthermore there was marked variation in the time elapsing from onset of post-radioiodine hypothyroidism to achievement of a given maintenance dose. These findings may be explained by persistence of non-TSH mediated thyroid function, after radioiodine therapy for Graves' thyrotoxicosis. The observations indicate the potential risk of overtreatment with thyroxine in post-radioiodine hypothyroidism unless the dose is carefully titrated against serum TSH levels. Final thyroxine requirements may not be evident in the initial phase of treatment and patients with apparently low maintenance thyroxine requirements require long-term follow up.

Changes in the properties of the thyrotropin receptor antibody in patients with Graves' disease after radioiodine treatment

We investigated the effect of a single dose of 131I upon thyrotropin receptor antibodies (TRAb) in 21 patients with Graves' disease. The thyrotropin receptor antibodies were assessed by parallel measurements of thyrotropin binding inhibitor immunoglobulin (TBII), thyroid stimulating antibody (TSAb) and thyroid stimulation blocking antibody (TSBAb) in serum by radoreceptor assay, stimulation of adenlate cyclase and inhibition of TSH-stimulated adenylate cyclase activation in FRTL-5 cells, respectively. Prior to radioiodine treatment, TBII was detected in all 21 patients and TSAb in 19 patients. After radioiodine treatment, TBII activities did not change during the 12-months observation period, but in eight patients TSAb activities gradually decreased and were undetectable at the end of the 12-month observation period. Persistence of TSAb was not associated with the clinical outcome. Eight patients developed hypothyroidism within one year after radioiodine treatment. Three of the hypothyroid patients developed TSBAb, and the appearance of TSBAb coincided with the development of hypothyroidism. These results suggest that TSBAb might develop after radioiodine treatment in a minority of patients with Graves' disease and that the appearance of TSBAb, in addition to radiation-induced thyroid destruction, might be involved in the development of hypothyroidism following radioiodine treatment.

Autoimmune thyroid disease: immunological, pathological, and clinical aspects

Autoimmune thyroiditis, most notably Hashimoto's thyroiditis, appears to be increasing in prevalence and is now more easily detected by sensitive laboratory tests and more invasive procedures such as fine needle aspiration. During the last decade, marked progress has been made in the understanding of these diseases. There is a greater awareness of the interaction between the humoral and cell-mediated arms of the immune system in autoimmune thyroiditis. Recent studies implicate a subpopulation of suppressor T lymphocytes which have an antigen-specific defect, resulting in their suboptimal interaction with the helper T lymphocytes and subsequent autoimmune manifestations. There is some evidence that thyroid epithelial cells which inappropriately express HLA-DR may enhance presentation of thyroid antigens to the immune system, possibly significant in the initiation or enhancement of the autoimmune response. The presence of various antithyroid autoantibodies allows the use of laboratory assays to confirm the clinical diagnosis and predict the results of treatment. There appears to be predisposing genetic factors in the development of autoimmune thyroiditis, with some geographical and racial differences. Environmental factors, most notably dietary intake of iodine, have also been implicated in the pathogenesis of Hashimoto's thyroiditis. Several animal models have been developed addressing such issues. Ongoing studies in the areas of postpartum thyroiditis and childhood thyroiditis are helpful in clarifying their relationship with Hashimoto's thyroiditis. Graves' disease and postpartum thyroiditis are being investigated as possible causes of postpartum depression. The association of Hashimoto's thyroiditis and carcinoma of the thyroid gland is still controversial, but its relationship with malignant lymphoma is now well accepted. Thus, although the pathogenesis of autoimmune thyroiditis remains elusive, there has been significant refinement of the clinical diagnosis, and immunological abnormalities of specific intrathyroidal lymphocytes have been identified. Hopefully, these new areas of knowledge will assist in the treatment of these diseases and in the prevention of the development of malignant lymphomas of the thyroid gland.

The relationships between serum T3 index, thyroid volume, and thyroid stimulating, TSH receptor binding and thyroid growth stimulating antibodies in untreated Graves' disease

This study represents an international double-blind collaborative study of abnormal immunoglobulin activity in untreated Graves' disease. Laboratories in two countries participated in a comparison of thyrotrophin binding inhibiting (TBII), thyroid stimulating (TSAb), and growth stimulating (TGI) immunoglobulins with clinical data, including ultrasonically measured thyroid size. The correlation between TGI and thyroid volume (n = 25, Rs = 0.54, P less than 0.05) and the fact that 9 of 10 patients with high range TGI values had large goitres establish the relationship between TGI and goitre, confirming that the in-vitro activity of these antibodies is related to an in-vivo action. In addition, both TBII and TSAb correlated with serum free T3 indices (TBII: n = 60, Rs = 0.46, P less than 0.001, and TSAb: n = 60, Rs = 0.64, P less than 0.001). Moreover, both TBII and TSAb correlated with thyroid volume (TBII: n = 60, Rs = 0.37, P less than 0.01, and TSAb: n = 60, Rs = 0.41, P less than 0.01) suggesting that these antibodies are also important in development of goitre in Graves' disease. Finally, some correlation between the antibodies was observed. TBII correlated with TSAb (n = 60, Rs = 0.47, P less than 0.001), and in the 16 patients with positive TGI results, this activity correlated with TBII (Rs = 0.54, P less than 0.05), but not with TSAb. Also some cases were found with corresponding high range TBII and TGI, while negative for TSAb, suggesting a close relationship between the in-vitro measurement of TSH binding and TGI.

Hyperthyroidism due to Graves' disease and due to autonomous goiter

An attempt was made to classify 326 patients with hyperthyroidism due to Graves' disease and due to autonomous goiter in an area of endemic iodine deficient goiter using the following two sets of criteria: Primary criteria: the presence of endocrine ophthalmopathy (Graves' disease) and the absence of endocrine ophthalmopathy and the absence of microsomal antibodies greater than or equal to 1:1600 (autonomous goiter). Sixty-nine percent of the patients could be divided in the two groups with the aid of these criteria. Secondary criteria: age greater than 50 years, presence of a goiter, presence of thyroid nodules, activity distribution in the scan, iodine intake determined by iodine excretion in the urine. These criteria had to be applied in the 31% of the patients who could not be divided into one of the two groups using the primary criteria. The secondary criteria were accumulative. Using these criteria 55% of the 326 patients were classified as having Graves' disease and 45% as having autonomous goiter. The probability of correct grouping when both primary and secondary criteria were applied was estimated to be 90% compared to 54% when we used only the classical terms, i.e. endocrine ophthalmopathy and diffuse goiter on the one hand and multinodular goiter without endocrine ophthalmopathy on the other hand. In a second group of 120 hyperthyroid patients classified in this way, thyrotropin displacing activity was determined independently. Its prevalence was 79% in patients classified as having Graves' disease but only 3% in those classified as having autonomous goiter. The prevalence of TDA observed in patients who presumably had autonomous goiter was in the same range as in the following groups: 45 normal individuals; 126 patients with euthyroid goiter; and in 112 patients with euthyroid and hyperthyroid autonomous adenoma.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunologic factors in thyroid disease

The role of immunologic reactions against orbital-specific and orbital-thyroid antigens in the pathogenesis of autoimmune thyroid disorders and Graves' ophthalmopathy is discussed. Possible mechanisms for the association of ophthalmopathy and autoimmune thyroid disorders is discussed in relation to the role of autoantibodies against eye muscle antigens.

The pathogenesis of Graves' disease

The abnormally increased thyroid activity that is characteristic of Graves' disease is caused by immunoglobulins which specifically interact with the thyroid cell and stimulate it. Increases and decreases in thyroid activity in Graves' disease can be clearly related to rise and fall of these immunoglobulin-mediated activities. The level of immunoglobulin stimulatory activity can be used for prediction of the likelihood of neonatal Graves' disease and of recurrence of disease after cessation of treatment with antithyroid drugs. Investigation of patients with Graves' disease and their families has led to identification of particular human leukocyte antigens and genetically linked markers on immunoglobulins which both appear to incur increased susceptibility to certain autoimmune diseases. Differences in immune function, when compared with control populations, have been found in patients with these genetically linked markers. Protection against autoimmune disease is maintained by purposeful inhibition of any self-directed activity within each function of the immune system and by the controlling interaction of other immune functions. No single deficiency of immune function can be selected as giving the major risk of autoimmune disease, but rather a sum of relative defects resulting in an increased risk. In some patients with Graves' disease the self-protection mechanisms regain sufficient control of the immune functions to reduce the activity of the autoimmune disease, and the patient may achieve clinical remission. Often, however, there is evidence that abnormal immune activity directed against thyroid tissue has persisted with liability to recurrence of the Graves' disease.

The effect of radioiodine and antithyroid drugs on serum long acting thyroid stimulator protector (IATS-P). A three year prospective study

Over a three year period we have studied the effect of either a one year course of Carbimazole or a single dose of radioiodine in a group of 46 patients with Graves' disease. Initially, in untreated patients LATS-P was present in 39 (85%) but at the end of the study was only detectable in 19 (41%). The clinical outcome in 29 patients initially treated with carbimazole correlated well with changes in serum LATS-P which persisted in 18. Thirteen of these ultimately required radioiodine or sub-total thyroidectomy. With radioiodine two patterns of response were seen, in some LATS-P levels declined, whereas in others transient increases were seen usually during the first year but subsequently fell. There was no difference in clinical response between the two groups. Overall, the study indicates that serum LATS-P is related to the clinical course of Graves' disease but there remains a minority of patients in whom the activity cannot be detected.

The assay of Graves' immunoglobulins: a comparison of different methods

A multiplicity of techniques has arisen for the measurement of the immunoglobulins specifically associated with Graves' hyperthyroidism, which has led to difficulty in assessing the clinical significance of these immunoglobulins. In this study of untreated toxic Graves' disease we have taken two assays (LATS protector and thyrotrophin binding inhibiting immunoglobulin, TBII) which depend upon the measurement of binding to thyroid cell membranes, and correlated them with a bioassay which measures as the index of activity the biologically relevant end point of T3 secretion from thyroid tissue. The frequency of positive responses obtained with each method was similar to that of previous studies; combining the results a positive response was found in 100%. No significant correlation was found between any of these three assays. T3 to assess which method relates most closely to circulating thyroid hormone levels in vivo. A highly significant correlation was obtained for TSAb measured by T3 secretion with both total serum T3 and total serum T4 levels. A positive correlation was also found for LATS protector, but not for TBII. We conclude that although these assays are specific for Graves' immunoglobulins, they are measuring closely related but not identical immunoglobulin activities.

The influence of cyclosporin a on experimental autoimmune thyroid disease in the rat

Female PVG/c rats, thymectomized on weaning and given 4 courses of whole body irradiation to a total dose of 1000 rads, developed experimental autoimmune thyroid disease (EAITD) as assessed by histological evidence of thyroiditis and circulating levels of antithyroglobulin antibodies. Hypothyroidism resulted. Induction of the disease was associated with a highly significant fall in T lymphocyte numbers. Eight weeks after their last dose of irradiation the animals commenced treatment with Cyclosporin A (10 mg/kg rat/day, intragastrically) and were treated for varying time intervals thereafter. The reversal of the T lymphocyte helper: suppressor ratio on Cyclosporin A therapy was associated with a significant improvement in the disease process. The alterations in the T cell subsets and in the disease lasted only as long as the drug was administered and thereafter reverted towards that seen in the control groups of animals receiving no treatment.

Effect of radioiodine on stimulatory activity of Graves' immunoglobulins

The effects of 131I therapy on the activity of thyroid stimulating antibody (TSAb) and thyrotrophin binding inhibiting immunoglobulin (TBII) in nineteen patients with Graves' disease have been studied. Prior to 131I administration TSAb was detected in 84%, and TBII in 68% of patients. Following 131I administration TSAb and TBII were detectable in 100% of patients. The elevation 3 months after treatment of the means of both the TSAb and TBII indices for the group of nineteen patients was highly significant compared with pre treatment values. All the patients went into remission during the course of the study and the TSAb index declined in all patients, becoming undetectable in eleven; TBII also declined in most patients but remained detectable in thirteen. The study furthermore afforded the opportunity for a direct comparison of binding with stimulatory activity. These results show that after 131I therapy for Graves' hyperthyroidism there is a transient increase in TSAb as well as TBII, followed by a decline, and that the measurement of binding and stimulatory activities are in good general agreement.

Thyroid stimulating antibodies, thyroglobulin antibodies and serum proteins during treatment of Graves' disease with radioiodine or propylthiouracil

The relation between serum concentrations of thyroglobulin antibodies (TgAb), thyroid-stimulating antibodies (TSAb) and serum immunoglobulins during treatment of Graves' disease was studied in 36 consecutive patients treated randomly with 131-iodine (n = 16) or propylthiouracil (n = 20). The patients were investigated before treatment was started and on seven occasions within the following year. In the entire patient group 78% were positive for TSAb and 47% for TgAb. There was a significant correlation between TSAb and TgAb in 15 patients concomitantly positive. There were no significant changes in serum immunoglobulins during treatment in either group of patients. In the radioiodine-treated group of patients TgAb was reduced after 1 week, whereas TSAb showed insignificant variations. After 5-10 weeks both antibodies increased, for TgAb with a median peak level 3 time above the initial concentration. Of 16 patients treated with radioiodine five developed myxoedema and four of these were positive for TgAb. There was a relation between the development of myxoedema and the ratio between increases of TSAb and TgAb. Increase in TSAb was not related to serum thyroglobulin (Tg) measured in TgAb-negative patients. Propylthiouracil showed minor effects on the studied variables, but with lower mean values of Tg, TgAb and TSAb at the end of the observation period. The results indicate an immunological relation between TSAb and TgAb, although differences between their course exist in some situations.

Influence of treatment with radioiodine and propylthiouracil on thyroid stimulating immunoglobulins in Graves' disease

Thyroid stimulating immunoglobulins (TSAb) were measured in fifty-four patients with Graves' disease before treatment with either radioiodine (seventeen patients) or propylthiouracil (PTU) (thirty-seven patients), and followed during treatment. After radioiodine TSAb increased to levels exceeding pretreatment values, and became detectable in three of six originally TSAb negative patients. In most patients TSAb decreased during treatment with PTU, and became undetectable after a mean of 12 months in patients above 40 years, and after a mean of 6 months in patients below 40 years. In order to eliminate the presumed causative agent in Graves' disease, antithyroid treatment should be at least 18 months in patients above 40 years, and at least 12 months in patients below 40 years of age. In twenty-nine patients TSAb were measured at cessation of 2 years antithyroid drug therapy. Ten patients were TSAb positive and all except one relapsed. Five of nineteen TSAb negative patients relapsed. Although TSAb positivity predict relapse, it is not an ideal index of prognosis after antithyroid therapy.

Carbimazole and autoantibody synthesis in Hashimoto's thyroiditis

Serum thyroxine, thyrotrophin, and thyroid microsomal antibody levels were measured in 20 patients with Hashimoto's thyroiditis and hypothyroidism before, during, and after treatment with carbimazole or placebo. Thyroid microsomal antibody levels fell during treatment in the 10 patients who received carbimazole, while serum thyroxine and thyrotrophin levels did not change. There were no changes in the placebo group. The study proves support for the concept that carbimazole may act directly on autoantibody synthesising lymphocytes localised in the thyroid. Such an effect might be valuable in influencing the autoimmune process in autoimmune thyroid disease.