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

The Role of Nuclear Medicine in the Clinical Management of Benign Thyroid Disorders, Part 1: Hyperthyroidism

Benign thyroid disorders, especially hyper- and hypothyroidism, are the most prevalent endocrine disorders. The most common etiologies of hyperthyroidism are autoimmune hyperthyroidism (Graves disease, GD), toxic multinodular goiter (TMNG), and toxic thyroid adenoma (TA). Less common etiologies include destructive thyroiditis (e.g., amiodarone-induced thyroid dysfunction) and factitious hyperthyroidism. GD is caused by autoantibodies against the thyroid-stimulating hormone (TSH) receptor. TMNG and TA are caused by a somatic activating gain-of-function mutation. Typical laboratory findings in patients with hyperthyroidism are low TSH, elevated free-thyroxine and free-triiodothyronine levels, and TSH-receptor autoantibodies in patients with GD. Ultrasound imaging is used to determine the size and vascularity of the thyroid gland and the location, size, number, and characteristics of thyroid nodules. Combined with lab tests, these features constitute the first-line diagnostic approach to distinguishing different forms of hyperthyroidism. Thyroid scintigraphy with either radioiodine or ^99mTc-pertechnetate is useful to characterize different forms of hyperthyroidism and provides information for planning radioiodine therapy. There are specific scintigraphic patterns for GD, TMNG, TA, and destructive thyroiditis. Scintigraphy with ^99mTc-sestamibi allows differentiation of type 1 from type 2 amiodarone-induced hyperthyroidism. The radioiodine uptake test provides information for planning radioiodine therapy of hyperthyroidism. Hyperthyroidism can be treated with oral antithyroid drugs, surgical thyroidectomy, or ¹³¹I-iodide. Radioiodine therapy is generally considered after failure of treatment with antithyroid drugs, or when surgery is contraindicated or refused by the patient. In patients with TA or TMNG, the goal of radioiodine therapy is to achieve euthyroid status. In GD, the goal of radioiodine therapy is to induce hypothyroidism, a status that is readily treatable with oral thyroid hormone replacement therapy. Dosimetric estimates based on the thyroid volume to be treated and on radioiodine uptake should guide selection of the ¹³¹I-activity to be administered. Early side effects of radioiodine therapy (typically mild pain in the thyroid) can be handled by nonsteroidal antiinflammatory drugs. Delayed side effects after radioiodine therapy for hyperthyroidism are hypothyroidism and a minimal risk of radiation-induced malignancies.

131I-Induced Graves' disease in patients treated for toxic multinodular goitre: systematic review and descriptive analysis

BACKGROUND

Graves' disease (GD) arising after the treatment of toxic multinodular goitre (TMNG) with radioiodine has long been described but it remained unclear whether GD was in fact iodine induced, its incidence, risk factors, natural history and treatment outcomes.

METHODS

A systematic search using The Cochrane Library, Medline and PubMed Central allowed the pooling of data from 3633 patients with thyroid autonomy, 1340 patients with TMNG, to fill gaps in knowledge, regarding the clinical expression of iodine-induced GD (131I-IGD) in adults.

RESULTS

131I-IGD developed in 0-5.3% of those with thyroid autonomy (first year) and in 5-5.4% of those with TMNG, 3-6 months after treatment. Patients with toxic adenoma were less affected. 131I-IGD was more common in patients with pre-treatment direct or indirect signs of autoimmunity: positive anti-TPO (p < 0.05), glandular hypoechogenicity, TRAbs within reference range, diffuse uptake on 99mTc-pertechnetate scans (p < 0.05), findings that may increase the risk tenfold. 131I-IGD manifested 3 months after 131I, justifying 15.4-29% of cases of relapse. The rate of spontaneous remission was 17-20% (6 months) and the rate of relapse after a second 131I treatment 22-25%. The use of an uptake-based administered 131I activity led to a greater proportion of euthyroid patients (78% compared to 25-50% with the mass-based approach).

CONCLUSIONS

GD may be triggered by 131I. The incidence of the condition is low. Several risk factors were consistently identified; some have shown to raise the risk significantly. 131I-IGD seems more treatment resistant than iodine-independent GD and the best resolution rates were achieved with uptake-based selected iodine activities.

Graves disease following radioiodine therapy for toxic adenoma: Clinical case report

RATIONALE

There is a low risk of developing Graves disease (GD) with elevated thyrotropin receptor antibodies (TRAbs) in patients undergoing radioiodine therapy for toxic adenoma.

PATIENT CONCERNS

An old female patient with a history of Hashimoto thyroiditis was referred to our department due to thyrotoxic symptoms. After the administration of radioiodine, a significant remission was achieved. However, after 4 months, she was referred to our department again due to recurrence of hyperthyroid symptoms.

DIAGNOSES

Based on the results of laboratory test, thyroid scan and ultrasound examination, she was diagnosed as thyrotoxicosis induced by toxic adenoma at the first visit. However, 4 months later, she was diagnosed as Graves' disease at the second visit.

INTERVENTIONS

She received radioiodine therapy two times with different doses of 15 mCi and 12 mCi.

OUTCOMES

After the administration of 15 mCi radioiodine, her thyroid hormones and clinical symptoms showed significant improvement. However, 4 months later, she presented thyrotoxicosis again. After the second radioiodine therapy with a lower dose, her clinical symptoms moved towards normalization during regular follow up.

LESSONS

Toxic adenoma and GD are considered as 2 distinct disease entities; however, radioiodine therapy for toxic adenoma may induce GD. We should learn to differentiate these 2 disorders prior to radioiodine therapy because of different treatment strategies and goals.

Graves' disease during immune reconstitution in HIV-infected patients treated with HAART

Autoimmune phenomena after immune recovery due to HAART are not frequently described. Recently we found 3 patients with Graves' disease after starting HAART, outnumbering the expected incidence; 13 patients have been reported in the literature up to the present time.A probable relation between immune restoration and development of Graves' disease might be suspected.

Incidence of postradioiodine immunogenic hyperthyroidism/Graves' disease in relation to a temporary increase in thyrotropin receptor antibodies after radioiodine therapy for autonomous thyroid disease

BACKGROUND

The aim of the study was to analyze retrospectively the incidence of postradioiodine immunogenic hyperthyroidism/Graves' disease in relation to a temporary increase in TSH-receptor antibodies without overt hyperthyroidism after radioiodine therapy for autonomous thyroid disease.

PATIENTS AND METHODS

Between May 2000 and May 2003 all patients (n = 1,357) who had undergone radioiodine therapy for autonomous thyroid disease were retrospectively analyzed for development of postradioiodine immunogenic hyperthyroidism. On pretreatment evaluation 565 of 1,357 patients (41.6%) had unifocal autonomous thyroid disease (UFA), 693 of 1,357 patients (51.1%) had multifocal autonomous thyroid disease (MFA), and 99 of 1,357 patients (7.3%) had diffuse thyroid disease (DISS). Free triiodothyronine (FT(3)), free thyroxine (FT(4)), thyrotropin (TSH), and thyroid antibodies were measured. Ultrasound examinations and thyroid scintigraphy were performed before and after radioiodine therapy. A sensitive assay with the human TSH receptor as antigen was chosen for measurement of the TSH receptor antibody and the study was limited to analysis of data obtained since introduction of this assay.

RESULTS

Fifteen of 1,357 patients (1.1%) (UFA, 8/565 = 1.4%; MFA, 6/693 = 0.9%; DISS 1/99 = 1.0%) developed postradioiodine hyperthyroidism between 1 and 13 months after radioiodine therapy with clinically overt hyperthyroidism and an elevation of TSH receptor antibodies. Patients with elevated thyroid peroxidase (TPO) antibodies before radioiodine therapy had an almost 10-fold (6/57 patients =10.5%) higher risk of developing postradioiodine immunogenic hyperthyroidism. Thirteen of 999 patients (1.3%) with antibody measurements after radioiodine therapy (UFA, 2/421 = 0.5%; MFA, 9/494 = 1.8%, DISS, 2/84 = 2.4%) had increased levels of TSH receptor antibodies and, to some extent, TPO antibodies without development of clinically overt hyperthyroidism.

CONCLUSIONS

There is an estimated 1.1% risk of developing postradioiodine immunogenic hyperthyroidism/Graves' disease in patients undergoing radioiodine therapy for autonomous thyroid disease and this increases approximately 10-fold when TPO antibody levels are elevated before radioiodine therapy. Furthermore, there is an estimated 1.3% risk of a temporary increase of TSH receptor antibodies after radioiodine therapy for autonomous thyroid disease without development of clinically overt hyperthyroidism.

Outcome of radioiodine-131 therapy in hyperfunctioning thyroid nodules: a 20 years' retrospective study

OBJECTIVE

To investigate the risk of hypothyroidism after radioiodine (131I) treatment for hyperfunctioning thyroid nodules.

DESIGN

Retrospective analysis of patients treated with 131I for hyperfunctioning thyroid nodules and followed up for a maximum of 20 years.

PATIENTS

A total of 346 patients treated with 131I in the years 1975-95, for a single hyperfunctioning nodule.

MEASUREMENTS

Hypothyroidism was defined as TSH levels > 3.7 mU/l. Kaplan-Meier survival analysis was used to analyse permanence of euthyroidism after 131I. A stepwise Cox proportional hazard model was used to identify factors influencing the progression to hypothyroidism.

RESULTS

The cumulative incidence of hypothyroidism was 7.6% at 1 year, 28% at 5 years, 46% at 10 years and 60% at 20 years. Age (P < 0.01), 24-th 131I uptake (P < 0.05) and previous treatment with methimazole (MMI, P < 0.1) were associated with a faster progression towards hypothyroidism, while thyroid and nodule size, thyroid status at diagnosis and degree of extranodular thyroid parenchymal suppression had no influence. In hyperthyroid patients with partial parenchymal suppression, however, previous MMI treatment was the most important prognostic factor (P < 0.01).

CONCLUSIONS

After 20 years of follow-up, 60% of patients treated with 131I for a single hyperfunctioning nodule are hypothyroid. Factors increasing the risk of hypothyroidism are age, 131I uptake and MMI pretreatment. The prognostic value of this last factor, however, depends on the degree of suppression of the extranodular thyroid parenchyma at the scan.

Incidence of radiation-induced Graves' disease in patients treated with radioiodine for thyroid autonomy before and after introduction of a high-sensitivity TSH receptor antibody assay

Autoimmune hyperthyroidism may occur several months after radioiodine therapy (RIT) for functional thyroid autonomy. Exacerbation of pre-existing subclinical Graves' disease (GD) has been held responsible for this phenomenon. Determination of TSH receptor antibody using solubilised porcine epithelial cell membranes is insensitive and may have failed to diagnose GD in these patients before RIT. Following the introduction of a more sensitive assay, using the human TSH receptor as an antigen, it has been expected that the incidence of radiation-induced GD after RIT for functional thyroid autonomy will be reduced. In a first group of 1,428 patients treated between November 1993 and March 1997 (group I) we used the porcine TRAb assay to exclude GD, while in a second group comprising 1,408 patients treated between January 2000 and December 2001 (group II), GD was excluded using the human TRAb assay. A matched control group of 231 patients was derived from group II. In group I a total of 15 (1.05%) patients developed obvious or suspected radiation-induced GD, while in group II 17 (1.2%) did so; the interval until development of GD was 8.4 and 8.8 months, respectively, after RIT. Serum anti-thyroid peroxidase levels before RIT were elevated in 36.4% of group I patients and 47.1% of group II patients, but in only 5.6% of the control group. Other non-specific signs of mild immunopathy of the thyroid were seen retrospectively in 73.3%, 64.7% and 16.0% of the patients in these three groups, respectively. In conclusion, the introduction of a high-sensitivity TRAb assay did not reduce the incidence of autoimmune hyperthyroidism occurring late after RIT for functional thyroid autonomy, but mild immunopathy of the thyroid is seen more frequently in these patients and seems to be a predisposing factor in the development of radiation-induced GD.

Relapses of hyperthyroidism in patients treated with radioiodine for nodular toxic goiter: relation to thyroid autoimmunity

Relapses of hyperthyroidism after treatment with radioiodine for uni- or multi-nodular goiter may be accompanied by the appearance of TSAb. However, this phenomenon has only emerged from one retrospective study on Northern European patients, in which it was not possible to determine whether TSAb also appeared in treated patients who did not relapse. The present study aimed to assess the appearance, immunogenic nature and clinical characteristics of hyperthyroidism relapse after treatment with 131I for nodular toxic goiter in patients from the Mediterranean area. A retrospective study was performed on 76 consecutive patients, born and resident in Sicily and aged 56-80 yr at diagnosis, who were treated with radioiodine. Serum aliquots obtained from the patients before 131I treatment and during a follow-up of 36-144 months were assayed for TSAb and TPOAb. The clinical charts of the patients were also re-examined. Twenty-six out of 76 patients (36.8%) had a hyperthyroidism relapse after a first treatment with 131I. Eight of the 26 (30.7%) also relapsed after the second treatment. Three out of 26 (11.5%) relapsed after a third treatment. The 50 patients who required only one treatment and the 18 who relapsed only once were all TSAb-negative at baseline, while 3/8 (37.5%) who relapsed also after the second treatment were already TSAb-positive at baseline. TSAb became positive in 3/18 patients (16.7%) who relapsed once, and in 4/8 (50.0%) of those who relapsed after a second treatment. One of these 7 TSAb-positive relapsers was also already TPOAb-positive at baseline and another became TPOAb-positive after treatment. The presence of circulating TSAb in 3/76 (3.9%) patients before treatment for toxic goiter more probably points to a diagnosis of Marine-Lenhart's syndrome. In contrast, the de novo appearance of TSAb in the presence of hyperthyroidism relapse in 4/76 (5.3%) patients suggests the development of a Graves'-like disease after radioiodine treatment. This occurrence does not seem to have precise ethnic grounds, since the incidence we observed in Mediterranean patients was similar to that previously reported in Northern European patients.