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

[Treatment of Graves' disease in patients with thyroid eye disease]

Graves' disease (GD) is an autoimmune disease that is often complicated by thyroid eye disease (TED). Clinical presentations of TED can develop simultaneously with the manifestation of GD, after the manifestation of GD amid treatment, and before the development of thyrotoxicosis. Treatment of such patients is a difficult task, because on the one hand, it is necessary to take into account the clinical picture of thyrotoxicosis, and on the other - the symptoms of eye damage. The combination of the two pathologies determines the need for simultaneous treatment of GD and TED, and the choice of a treatment method for GD will depend on the manifestations of TED. This article presents current views on the treatment of GD with concomitant TED. The choice of GD treatment method will be largely determined by the clinical manifestations of TED and will be conducted jointly by endocrinologists and ophthalmologists.

Radioiodine therapy of Graves' disease

Graves' disease (GD), the most common cause of hyperthyroidism, is an autoimmune disease directly caused by circulating autoantibodies that bind and activate the TSH receptor, inducing metabolic activation of the thyroid gland; this may be associated with important cardiac (atrial fibrillation) and ocular (ophthalmopathy) complications. Treating GD with real curative intent implies the full elimination of the functioning thyroid parenchyma using surgery or radioactive iodine therapy (RAI). RAI has been used in humans with hyperthyroidism since 1941, thanks to the pioneering work of a physician (Dr. Saul Hertz) and a physicist (Dr. Arthur Roberts). The rationale of RAI is based on the effect of radiation of ¹³¹I on target cells leading to DNA damage, both directly, through breakage of molecular bonds, and indirectly through the formation of free radicals. In particular, irradiation causes a broad spectrum of cellular damage due to the production of reactive oxygen species and lipid peroxidation of the plasma membrane. Thus, RAI-related cellular death takes place through both apoptosis and necrosis. The aim of this review was to summarize indications, efficacy, safety profile, and dosimetric aspects of RAI treatment in patients affected by GD.

Effect of Different 131I Dose Strategies for Treatment of Hyperthyroidism on Graves' Ophthalmopathy

PURPOSE

The study aims to define the effect of different dose strategies on ophthalmic complications in patients with Graves' disease (GD).

METHODS

All the patients with GD and no or inactive ophthalmopathy (clinical activity score; CAS < 3) underwent Snellen chart examination, measurement of proptosis, thyroid volume, and radioactive iodine uptake, and randomized into 1 of 3 groups. In group 1, all the patients received fixed low dose (FLD) of 259 MBq of I, whereas in group 2, all the patients received fixed high dose (FHD) of 555 MBq, and in group 3, calculated dose (CD) was administered to deliver 5.55 MBq/g (thyroid weight) of I. All examinations were repeated 6 months after treatment. The measurement of thyroid function tests and clinical examination were repeated after 12 months.

RESULTS

We studied 92 patients (58 female and 34 male) with mean age of 38.2 ± 12.0 years. Overall, 29, 32, and 31 patients were studied in FLD, FHD, and CD groups, respectively. The patients in CD received a mean activity of 240.5 MBq. The 3 groups were not significantly different regarding age, sex ratio, radioactive iodine uptake, smoking, visual acuity, and proptosis. The response rate 12 months after radioactive iodine therapy was 66.7%, 94.4%, and 92.9% in FLD, FHD, and CD groups, respectively (P = 0.05). Overall, CAS was increased significantly after treatment. Delta proptosis and delta CAS were increased significantly in FHD group compared with other groups (P < 0.05). The highest increment in proptosis was seen in FHD group.

CONCLUSIONS

The administration of 5.55 MBq/g of I has fewer ophthalmic complications compared with high fixed dose model and is more effective than low fixed dose strategy.

Thyroid-Associated Orbitopathy and Biomarkers: Where We Are and What We Can Hope for the Future

Background

Thyroid-associated orbitopathy (TAO) is the most common autoimmune disease of the orbit. It occurs more often in patients presenting with hyperthyroidism, characteristic of Graves' disease, but may be associated with hypothyroidism or euthyroidism. The diagnosis of TAO is based on clinical orbital features, radiological criteria, and the potential association with thyroid disease. To date, there is no specific marker of the orbital disease, making the early diagnosis difficult, especially if the orbital involvement precedes the thyroid dysfunction.

Summary

The goal of this review is to present the disease and combine the available data in the literature concerning investigation of TAO biomarkers.

Conclusions

Despite the progress done in the understanding of TAO disease, some important pieces are still missing. Typically, for the future, major efforts have to be done in the discovery of new biomarkers, validation of the suspected candidates on multicenter cohorts with standardized methodologies, and establishment of their clinical performances on the specific clinical application fields in order to improve not only the management of the TAO patients but also the therapeutic options and follow-up.

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.

The tale of radioiodine and Graves' orbitopathy

BACKGROUND

Autoimmunity against the thyrotropin receptor (TSH-R) is a key pathogenic element in Graves' disease (GD) and the autoimmune aberration may be modified by antithyroid treatment. An association between radioactive iodine (RAI) therapy for GD and the development or worsening of Graves' orbitopathy (GO) is widely quoted. RAI-associated leakage of thyroid antigen(s) leads to an increased production of TSH-R antibodies that may initiate the eye injury.

SUMMARY

RAI therapy leads to prolonged worsening of autoimmunity against the TSH-R, and the number of patients entering remission of TSH-R autoimmunity is considerably lower than with other antithyroid therapies. Scientific evidence has indicated that RAI treatment for GD is associated with increased risk of occurrence or progression of GO compared with antithyroid drugs (ATD) and thyroid surgery. The risks of developing new GO or worsening of preexisting GO is around 20% after RAI and around 5% after ATD. The risk of developing severe GO after RAI is around 7%. Smoking, high levels of pretreatment serum triiodothyronine, and post-RAI hypothyroidism are associated with increased risk of GO, whereas a high TSH-R autoantibody titer is an independent risk factor for the progression of GO. In patients with mild preexisting GO, steroid prophylaxis is effective in preventing deterioration of GO. Also, routine use of prophylactic oral steroids with RAI therapy should be considered in GD patients without overt GO, but even more so in those at higher risks of eye complications such as smokers, old men, and those with severe hyperthyroidism or high TSH-R antibody titers.

CONCLUSION

In contrast to ATD, remission of TSH-R autoimmunity after RAI therapy is less common, and RAI for GD is associated with definite increased risk of GO. Oral steroids are beneficial for patients with preexisting GO, particularly smokers.

TSH-receptor autoimmunity in Graves' disease after therapy with anti-thyroid drugs, surgery, or radioiodine: a 5-year prospective randomized study

INTRODUCTION

Autoimmunity against the TSH receptor is a key pathogenic element in Graves' disease. The autoimmune aberration may be modified by therapy of the hyperthyroidism.

OBJECTIVE

To compare the effects of the common types of therapy for Graves' hyperthyroidism on TSH-receptor autoimmunity.

METHODS

Patients with newly diagnosed Graves' hyperthyroidism aged 20-55 years were randomized to medical therapy, thyroid surgery, or radioiodine therapy (radioiodine was only given to patients > or = 35 years of age). L-thyroxine (L-T4) was added to therapy as appropriate to keep patients euthyroid. Anti-thyroid drugs were withdrawn after 18 months of therapy. TSH-receptor antibodies (TRAb) in serum were measured before and for 5 years after the initiation of therapy.

RESULTS

Medical therapy (n=48) and surgery (n=47) were followed by a gradual decrease in TRAb in serum, with the disappearance of TRAb in 70-80% of the patients after 18 months. Radioiodine therapy (n=36) led to a 1-year long worsening of autoimmunity against the TSH receptor, and the number of patients entering remission of TSH-receptor autoimmunity with the disappearance of TRAb from serum during the following years was considerably lower than with the other types of therapy.

CONCLUSION

The majority of patients with Graves' disease gradually enter remission of TSH-receptor autoimmunity during medical or after surgical therapy, with no difference between the types of therapy. Remission of TSH-receptor autoimmunity after radioiodine therapy is less common.

Serum thyrotropin in Graves' disease: a more reliable index of circulating thyroid-stimulating immunoglobulin level than thyroid function?

OBJECTIVE

To assess the relationship between serum thyrotropin (thyroid-stimulating hormone or TSH) on one hand and thyroid-stimulating immunoglobulin (TSI), free thyroxine (T4), and triiodothyronine (T3) levels on the other in Graves' disease, inasmuch as TSH may be suppressed in the presence of TSI because TSI may bind to the TSH receptor on the thyroid gland membrane and thus eliminate the need for circulating TSH for stimulating the thyroid gland.

METHODS

We determined serum TSI levels in 37 women and 13 men with Graves' disease, stratified into 4 groups on the basis of serum TSH levels irrespective of serum free T4 and T3 levels. Our reference ranges were 0.72 to 1.74 ng/dL for free T4, 80 to 200 ng/dL for T3, and 0.4 to 4.0 micro/mL for TSH.

RESULTS

Mean serum TSI concentrations were highest (215% +/- 28%) in patients with undetectable TSH levels (<0.03 micro/mL) and lowest (103% +/- 9%) in those with supernormal TSH concentrations (>4.0 micro/mL). TSI levels were intermediate in the other study groups: 157% +/- 16% in patients with subnormal though detectable TSH levels (0.03 to 0.39 micro/mL) and 125% +/- 12% in those with normal TSH levels (0.4 to 4.0 micro/mL). Moreover, a progressive decline in TSI levels with increasing serum TSH concentrations was noted, along with a significant negative correlation (r = -0.45; P<0.01) between serum TSI and TSH concentrations. Finally, relationships between free T4 and T3 levels on one hand and TSI or TSH levels on the other were not significant, with a considerable variability in free T4 and T3 levels being noted in individual study groups.

CONCLUSION

Serum TSH is frequently suppressed after treatment with antithyroid drugs or radioiodine (131I), irrespective of clinical thyroid function as expressed by increased, normal, or decreased free T4 and T3 concentrations. In an individual patient with Graves' disease, the serum TSH level may be more reflective of the circulating TSI concentration than is thyroid gland function as expressed by free T4 and T3 concentrations and therefore may be as reliable a predictor of remission as TSI.

Postpartum recurrence of Graves' hyperthyroidism can be prevented by the continuation of antithyroid drugs during pregnancy

OBJECTIVE

Previous studies recommend the discontinuation of antithyroid drug (ATD) therapy during pregnancy in women with well-controlled Graves' hyperthyroidism (GH). In this study, we investigated whether this termination of ATD therapy during pregnancy is beneficial in terms of postpartum GH recurrence.

DESIGN

A nonrandomized, retrospective study.

PATIENTS

Sixty-five pregnant GH patients treated with maintenance doses of ATDs were assigned into two groups: ATD therapy was discontinued before delivery in Group 1, but continued during pregnancy and after delivery in Group 2.

MEASUREMENTS

The prevalence of postpartum recurrence or exacerbation of GH within 1 year after delivery was examined. Serum T4, T3 TSH, and TSH receptor antibody levels were measured.

RESULTS

In Group 1, 70.8% (17/24) of patients suffered a recurrence of GH within 1 year after delivery. In contrast, a postpartum exacerbation of GH was observed in only 29% (12/41) of patients in Group 2 (P < 0.01). Both exacerbations and recurrences of GH appeared primarily within 4-6 months after delivery. Apparent neonatal hypothyroidism and malformations were not observed in the offspring of either group.

CONCLUSION

Continuing antithyroid drug therapy throughout pregnancy prevents postpartum recurrence of Graves' hyperthyroidism without resulting in neonatal hypothyroidism or malformations.

Anti-TSH receptor antibodies in clinical practice

Anti-thyroid stimulating hormone receptor antibodies are pathophysiologic and clinical indicators in autoimmune thyroid diseases, not only in Graves' disease. The detection of these antibodies is useful for diagnostic and management purposes. The presence and titers of anti-TSH receptor antibodies, however, have to be interpreted in light of the clinical and other biological characteristics of each patient. Newer, more sensitive assays of anti-TSH receptor antibodies may increase their significance in the diagnosis and management of autoimmune thyroid diseases and Graves' disease.

Antithyroid drugs inhibit radioiodine-induced increases in thyroid autoantibodies in hyperthyroid Graves' disease

Methimazole (MMI) has been reported to affect prognosis in hyperthyroid Graves' disease patients treated with radioiodine (131I). In the present study, serum concentrations of thyroxine (T4), triiodothyronine (T3), thyroglobulin (Tg), thyrotropin-binding inhibitory immunoglobulin (TBII), thyroglobulin antibody (TgAb), and thyroid-peroxidase antibody (TPOAb) were measured serially for 1 year in patients with Graves' disease after 131I treatment either given alone (group 1, 41 patients) or followed by an antithyroid drug (group 2, 19 patients). The effect of antithyroid drugs on these parameters was analyzed retrospectively. Mean serum concentrations of T4 and T3 both decreased to normal within 3 months after 131I treatment in both groups. Serum Tg concentrations in group 1 showed significant transient increases (about four times the basal value) 1 month after 131I administration. Titers of TBII, TgAb, and TPOAb in group 1 also increased transiently after 131I treatment, with the maximum increase at 3 months. Antithyroid drugs significantly lessened 131I-induced increases in serum concentrations of Tg and all thyroid autoantibodies tested. One year after 131I treatment, 33 of 41 patients (80%) were euthyroid or hypothyroid in group 1; this was true for only 4 of 19 group II patients (22%). The results indicate that administering antithyroid drugs after 131I treatment reduced 131I-induced damage to the thyroid and reduced therapeutic efficacy of 131I in hyperthyroidism. Drug treatment also inhibited release of Tg and blunted 131I-induced increases in titers of thyroid autoantibodies.

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.

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.

Intercellular adhesion molecule-1 (ICAM-1) in the sera of patients with Graves' disease: correlation with disease activity and treatment status

Intercellular adhesion molecule (ICAM-1), a ligand for lymphocyte function-associated antigen-1 (LFA-1), plays an important role in a variety of immune-mediated mechanisms such as lymphocyte attachment to cultured Graves' thyroid cells. We report the detection of a soluble form of the ICAM-1 molecule (sICAM-1) in sera from patients with Graves' disease (GD) and other thyroid disorders. The mean (+/- SD) sICAM-1 concentration in 28 euthyroid control subjects was 1931 +/- 681 pmol/L. The mean sICAM-1 concentration in 25 untreated hyperthyroid patients with GD was significantly elevated (3065 +/- 890 pmol/L), and decreased significantly (2489 +/- 845 pmol/L) after treatment with antithyroid drugs and/or 131I. Of 14 GD patients who had been in remission following administration of antithyroid drugs, 12 had recurrent disease. In 10 of the 12 patients in whom GD recurred, the sICAM-1 concentration (3807 +/- 796 pmol/L) increased significantly. The mean sICAM-1 concentration in patients with hypothyroidism due to chronic thyroiditis (n = 15:2895 +/- 569 pmol/L) was significantly elevated over that of control subjects, and not different from untreated hyperthyroid patients. The mean sICAM-1 concentration in patients with subacute thyroiditis (n = 13: 3036 +/- 441 pmol/L) was significantly elevated, while the mean sICAM-1 concentration in patients with nodular goiter (n = 10: 2318 +/- 490 pmol/L) was within the normal range. These results indicate that mean serum sICAM-1 concentration was significantly elevated in patients with untreated GD, and it decreased after treatment and increased at the time of recurrence. Therefore, the elevated serum concentration of sICAM-1 in patient with GD probably reflects ongoing immune processes.