Radioactive Iodine for the Treatment of Subclinical Thyrotoxicosis Grade 1 and 2: Outcome of up to 18-Year Follow Up

BACKGROUND

Subclinical thyrotoxicosis (SCT) is associated with significant morbidity and mortality, specifically increased risk of atrial fibrillation and cardiovascular death. The management is ill-defined due to the scarcity of randomised controlled studies. Some clinicians recommend radioiodine (RAI) treatment however its long-term outcome is unknown. Therefore, further data is needed to provide robust evidence-based guidelines.

METHODS

A prospective, single-protocol analysis of the outcome of SCT patients (Grade 1; 0.1-0.4 mIU/L and Grade 2; <0.1 mIU/L) treated with mean dose of 427 MBq of I¹³¹, followed up for up to 18 years. Thyroid function tests were measured at 4-6 weeks, 3-, 6-, and 12-months post-RAI, and annually thereafter. Cure was defined as achieving a euthyroid/hypothyroid state.

RESULTS

Seventy-eight patients with a median age of 68 years (range 36-84) and varying aetiology [55 toxic multinodular goitre (TMNG), 10 toxic nodule (TN) and 13 Graves' disease (GD)] were followed up for a median period of 7.5 years (range 1-18). The cure rate was 100%. The rates of hypothyroidism in TMNG, TN and GD were 23.6%, 30% and 38.5% respectively. The median time to hypothyroidism was 6 and 12 months in GD and TMNG/TN respectively. No differences in outcome between Grade 1 versus Grade 2 were observed.

CONCLUSION

RAI using single mean dose of 427 MBq is effective and safe, irrespective of aetiology or grade of TSH suppression. GD patients become hypothyroid within the first year, whilst TMNG/TN for up to 9-years. Thus after 12 months of follow up, annual thyroid function monitoring is advised.

Predicting outcomes and complications following radioiodine therapy in Graves' thyrotoxicosis

OBJECTIVE

Radioiodine (RAI) is an effective treatment for Graves' thyrotoxicosis but is associated with a failure rate of 15% and may be a risk factor for thyroid eye disease (TED) and weight gain. We sought to examine predictors of RAI failure, weight gain, TED and patient satisfaction.

DESIGN

Retrospective cohort study.

PATIENTS

A total of 655 episodes of RAI in Graves' thyrotoxicosis patients (2006-2015).

MEASUREMENTS

Biochemical assessment, including TFTs and thyrotropin receptor antibodies (TRAb), clinical features (eg, TED, weight and thionamide use) and patient questionnaire.

RESULTS

The treatment failure rate was 17%. Failure was greater with higher fT4 (P = 0.002) and higher TRAb (P = 0.004). Failure rate was 42.2% when TRAb >40 U/L. Median weight gain was 3.2 kg in those with normal fT4 prior to RAI and 5.8 kg when fT4 was elevated (P < 0.001). New TED developed in 7.6% but was not associated with post-RAI dysthyroidism. Treatment satisfaction was generally high (median response 8/10).

CONCLUSIONS

Treatment failure after RAI occurs in predictable groups and this should be reflected in the information provided to patients. Weight gain is common and may not entirely be explained by a return to pre-thyrotoxic baseline. We were unable to detect any significant impact of post-RAI dysthyroidism on weight gain, TED or thyroid symptoms in this large cohort.

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.

Clinical efficacy of radioiodine therapy in multinodular toxic goiter, applying an implemented dose calculation algorithm

Radioiodine is a common therapeutic option for Multinodular Toxic Goiter (MTG). We evaluated an algorithm for personalized radioiodine activity calculation. Ninety-three (28 male, 65 female; 43-84 years) patients with MTG eligible for radioiodine treatment (131I-iodide) were studied. The quantity of 131I-iodide to be administered was estimated by Thyroid Volume Reduction (TVR) algorithm, developed for Graves' disease. It takes into account 131I uptake, its effective half-life (T1/2eff), thyroid volume, and its expected reduction during treatment. A comparison with the activity calculated by other dosimetric protocols and the "fixed" activity method was performed. 131I uptake was measured by external counting, thyroid volume by ultrasonography (US), thyroid stimulating hormone (TSH), and thyroid hormones by standard immunometric methods. In a follow-up of 6-120 months, remission of hyperthyroidism after a single 131I-iodide treatment was observed in 76 patients (64 euthyroid, 12 hypothyroid). The thyroid volume reduction observed by US after the treatment fairly correlated with what predicted by our model; T1/2eff was highly variable and critically affected dose calculation. The administered activities (median 526 MBq, range 156-625 MBq) were slightly lower than the "fixed" activities (600 MBq) and with respect to the other protocols' prescriptions (-15/38%); the median 131I activity administered to relapsed patients (605 MBq) was significantly greater (P=0.01) with respect to the dose administered to cured patients (471 MBq). Our study shows that an effective cure of MTG can be obtained with relatively low 131I activities and probably with a relatively low incidence of hypothyroidism, using TVR method.

Radioiodine therapy in patients with type II amiodarone-induced thyrotoxicosis

INTRODUCTION

The treatment of amiodarone-induced thyrotoxicosis (AIT) still remains a clinical challenge, requiring the cooperation of both endocrinologists and cardiologists. Unfortunately, even today AIT is related to significantly increased mortality.

OBJECTIVES

The aim of this study was to compare the efficacy of radioidine therapy for type II AIT in 2 groups of patients: with high or normal radioiodine uptake and treated by amiodarone (AM) in the past (AM- group) and with low radioiodine uptake and currently treated with AM (AM+ group).

PATIENTS AND METHODS

The AM- group included 57 patients and the AM+ group, 49. All patients received iodine-131 at a dose of 22mCi~800. Patient data were collected for over 2 years.

RESULTS

After radioiodine administration, serum thyroid-stimulating hormone levels in the AM- group and AM+ group were 0.0 ±0.0 and 0.0 ±0.0, respectively, at 1 month; 1.2 ±3.3 and 0.6 ±1.2, respectively, at 12 months; and 4.2 ±3.6 and 1.9 ±0.8, respectively, at 2 years. All differences between the groups were statistically significant (P <0.0001). Free triiodothyronine and thyroxine levels were significantly higher in the AM+ group compared with the AM- group. During follow-up, death occurred in 22 patients in the AM+ group and 6 patients in the AM- group.

CONCLUSIONS

Radioiodine treatment is a safe and effective therapeutic modality for patients with type II AIT despite low radioiodine uptake, especially for patients with contraindications to other types of treatment (eg, thyroidectomy). Moreover, since thyrotoxicosis in patients with AIT is a significant risk factor for increased mortality, and since there are no alternative antiarrythmic treatments, radioiodine administration seems to be the only effective therapeutic modality.

Decreased birth weight, length, and head circumference in children born by women years after treatment for hyperthyroidism

CONTEXT

Whether hyperthyroidism influences the birth characteristics of children born several years after treatment is unknown.

OBJECTIVE

The objective of the study was to compare birth characteristics in singleton newborns delivered by women previously treated for Graves' disease (GD), toxic nodular goiter (TNG), or nontoxic goiter (NTG).

DESIGN

This was a nested case-control design within a national cohort registry study from 1950 through 2006.

SETTING

The study was conducted at a university and a hospital center in collaboration.

PATIENTS

The birth characteristics of newborns (n = 3421) delivered in a cohort of 43 633 women treated for GD or toxic nodular goiter by radioiodine or surgery (exposed group) at least 1 year prior to pregnancy were compared with newborns (n = 2914) of 45 655 mothers, previously operated for NTG (unexposed group).

MAIN OUTCOME

The primary outcome was birth weight, length, and head circumference. The secondary outcome was malformations, gestational age, and type of hyperthyroidism.

RESULTS

The birth weight of exposed children was 3431 ± 607 g (mean ± SD) compared with the unexposed, 3520 ± 641 g (P < .001). The cumulative odds ratio (OR) for lower birth weight was 1.29 [95% confidence interval (CI) 1.16-1.43]. The average birth length for the exposed children was 50.0 ± 2.7 cm compared with the unexposed of 50.4 cm ± 2.6 cm (P < .01) [cumulative OR 1.25 (95% CI 1.13-1.37)]. The head circumference was 34.5 ± 1.9 cm among exposed and 34.7 ± 1.8 cm, respectively (P < .001), with an OR of 1.24 (95% CI 1.13-1.35). No differences in birth characteristics were observed between children born after maternal GD or toxic nodular goiter.

CONCLUSIONS

Previous GD or TNG may influence the birth characteristics several years after radioiodine or surgical treatment.

Laser ablation and 131-iodine: a 24-month pilot study of combined treatment for large toxic nodular goiter

CONTEXT

It is normally recognized that the preferred treatment in large toxic thyroid nodules should be thyroidectomy.

OBJECTIVE

The aim of the study was to assess the efficacy of combined laser ablation treatment (LAT) and radioiodine 131 (131I) treatment of large thyroid toxic nodules with respect to rapidity of control of local symptoms, of hyperthyroidism, and of reduction of administered 131I activity in patients at refusal or with contraindications to surgery.

DESIGN AND SETTING

We conducted a pilot study at a single center specializing in thyroid care.

PATIENTS

Fifteen patients were treated with LAT, followed by 131I (group A), and a series of matched consecutive patients were treated by 131I only (group B).

INTERVENTION(S)

Laser energy was delivered with an output power of 3 W (1800 J per fiber per treatment) through two 75-mm, 21-gauge spinal needles. Radioiodine activity was calculated to deliver 200 Gy to the hyperfunctioning nodule.

MAIN OUTCOME MEASURE(S)

Thyroid function, thyroid peroxidase antibody, thyroglobulin antibody, ultrasound, and local symptoms were measured at baseline and up to 24 months.

RESULTS

Nodule volume reduction at 24 months was: 71.3 ± 13.4 vs 47.4 ± 5.5%, group A (LAT+131I) vs group B (131I), respectively; P < .001). In group A (LAT+131I), a reduction in radioiodine-administered activity was obtained (-21.1 ± 8.1%). Local symptom score demonstrated a more rapid reduction in group A (LAT+131I). In three cases, no 131I treatment was needed after LAT.

CONCLUSIONS

In this pilot study, combined LAT/131I treatment induced faster and greater improvement of local and systemic symptoms compared to 131I only. This approach seems a possible alternative to thyroidectomy in patients at refusal of surgery.

Predictors of treatment failure, incipient hypothyroidism, and weight gain following radioiodine therapy for Graves' thyrotoxicosis

BACKGROUND

Following radioiodine ((131)I) therapy, both late recognition of hypothyroidism and treatment failure may result in adverse outcomes.

AIM

We sought to assess indicators of both incipient hypothyroidism and treatment failure following (131)I and determine factors predictive of weight gain.

SUBJECTS AND METHODS

Retrospective study of 288 patients receiving (131)I for treatment of Graves' thyrotoxicosis. Primary outcome measures were thyroid status and weight change at 1 yr following (131)I.

RESULTS

The treatment failure rate at 1 yr was 13.5%. Hypothyroidism developed in 80.9%, with 58.5% of patients having levels of free T4 (fT4) <6 pmol/l at diagnosis. Patients receiving thionamides before and after (131)I had significantly higher levels of treatment failure (23.3%) than those with no thionamide exposure (6.3%, p=0.003), but also had more active Graves' disease. Following (131)I, development of a detectable TSH or low-normal fT4 levels was not associated with recurrent thyrotoxicosis. Median weight gain was 5.3 kg, although patients with nadir fT4 levels <6 pmol/l gained an average 2 kg more than those with levels >6 pmol/l (p=0.05). The main predictor of weight gain was fT4 level immediately prior to treatment; those in the lowest tertile gained a median 3.1 kg whilst those in the highest tertile gained 7.4 kg (median difference 4.3 kg; 95% confidence interval: 2.5-6.2).

CONCLUSIONS

Marked hypothyroidism following (131)I is common and often occurs early. Simple biochemical parameters may help identify incipient hypothyroidism and potentially limit excess weight gain. Treatment failure is common in patients with severe thyrotoxicosis and in such cases larger doses of (131)I may be warranted.

Amiodarone-induced thyrotoxicosis in a case of Eisenmenger's syndrome

Eisenmenger's syndrome is a condition due to any congenital heart defect with an intracardiac left-to-right communication that leads to pulmonary hypertension with reversed right-to-left blood flow and secondary cyanosis. The main complications of Eisenmenger's syndrome are heart failure and arrhythmias. Amiodarone, the drug of choice for arrhythmia treatment in such patients, can cause a number of complications, including amiodarone induced thyrotoxicosis (AIT). Hereby, we present a 41-year-old patient with Eisenmenger's syndrome who developed AIT and was successfully treated with radioactive iodine therapy. The patient had an accompanying heart failure and had been treated with amiodarone due to chronic atrial fibrillation. Twenty months later he developed an AIT for which was treated with 814 MBq (22 mCi) radioactive iodine. Since 7 weeks later only a slight decline in thyroid hormones was observed, the patient was received a transient treatment with methimazole, which had to be withdrawn soon due to severe leucopenia. Because of the need to maintain amiodarone, a second ablative radioactive iodine dose was administered leading to complete clinical remission. In conclusion, this case demonstrates that even though amiodarone reduces iodine uptake to a very low level, the therapy with radioactive iodine can be still effective if it is given in a repeated dose to patients who require continuation of amiodarone.

Efficiency of radioactive I-131 therapy in geriatric patients with toxic nodular goiter

BACKGROUND AND AIMS

The success of I-131 therapy in geriatric patients who were referred to an endocrinology clinic with toxic nodular goiter and who lived in iodine-deficiency regions was studied.

MATERIALS AND METHODS

Patients older than 60 years who received I-131 therapy were included via retrospective data analyses. Fifty-nine patients between 60 and 82 years of age were enrolled in the study. The patients received an oral capsular form of I-131 (10-25 mCi) and were followed up for 1 year with clinical and laboratory results. Euthyroid or hypothyroid status at the end of the year after treatment was deemed to be a response to treatment.

RESULTS

Of the 21 (36%) male and 38 (64%) female patients, 29 (49%) had a solitary toxic nodule and 30 (51%) had toxic multinodular goiter. Twenty-nine (49%) of the patients received propylthiouracil therapy. At the end of the year, 38 (64%) patients were euthyroid, 11 (19%) were hypothyroid, and 10 (17%) were thyrotoxic. Forty-nine (83%) patients who were euthyroid and hypothyroid were considered responders.

CONCLUSION

Geriatric patients with toxic nodular goiter were shown to have a high response rate to I-131 therapy. Thus, we suggest that radioactive iodine treatment should be the first-line treatment in these patients.

¹³¹I treatment of toxic nodular goiter under combined thyrostatic-thyromimetic medication is at low risk of late hypothyroidism

AIM

Treatment of toxic nodular goiter with ¹³¹I is a first-line therapy for hyperthyroidism. To avoid a thyrotoxic storm, ¹³¹I is usually administered after pretreatment with antithyroid drugs, with thyroid-stimulating hormone (TSH) increase and functional recruitment of inhibited normal tissue. Therefore, both autonomous nodule(s) and normal tissue are irradiated. This may be a reason for late hypothyroidism occurring in 15-25% of patients. This study aimed at assessing different pretreatment modalities with combined methymazole and triiodothyronine, achieving euthyroidism with suppressed TSH.

METHODS

After diagnosis of autonomously functioning toxic nodule, patients were subjected to thyrostatic medication. Two months later, TSH was checked; if >0.5 mU/L triiodothyronine treatment was associated. After 2 more months, if the TSH level was suppressed, patients received ¹³¹I-therapy. A total of 149 patients were consecutively enrolled, 41 of whom with uninodular and 108 with multinodular goiter. They were evaluated at diagnosis, pretreatment, 3 and 6 months after therapy and at late follow-up (6.8+/-4.2 years; range: 1-22 years).

RESULTS

Administered activity was calculated according to ¹³¹I uptake and gland weight. Methymazole was discontinued 6 days before treatment and T3 was maintained until administration of ¹³¹I-therapy. Euthyroidism was achieved in 88% of patients. At late follow-up, subclinical hypothyroidism was observed in 10 patients (6.7%) and overt hypothyroidism in 5 patients (3.3%). No pathological consequences or side effects of ¹³¹I-therapy were found during the 6.8+/-4.2 year follow-up period.

CONCLUSION

Treatment of toxic nodular goiter with ¹³¹I-therapy, under combined thyrostatic-thyromimetic treatment is a simple, safe, well-tolerated, and effective procedure.

Anaplastic thyroid carcinoma arising in long-standing multinodular goiter following radioactive iodine therapy: report of a case diagnosed by fine needle aspiration

BACKGROUND

Anaplastic thyroid carcinoma (ATC) is a highly aggressive, undifferentiated carcinoma that may arise on top of normal or abnormal thyroid. Making the diagnosis by fine needle aspiration (FNA) of the thyroid with a long-standing history of multinodular goiter (MNG) is not uncommon. We report a case discussing the cytopathologic findings and the relationship with long-standing goiter and thyroid exposure to radioactive iodine treatment.

CASE

A 90-year-old male patient presented with a > 45-year history of MNG that was associated with thyrotoxicosis and multiple courses of radioiodine (I-131) treatment. He developed recent symptoms of dyspnea, dysphagia, neck welling and uniintentional weight loss. Computed tomography of the neck was done revealing a large MNG with retrosternal extension and calcifications. FNA was performed revealing highly anaplastic cells with a colloid background and presence of neutrophils. The diagnosis of ATC was made. The patient refused any kind of management and was discharged upon his request. He died 2 days after the procedure, and no autopsy was performed.

CONCLUSION

ATC is an aggressive, undifferentiated thyroid carcinoma that can be diagnosed by FNA and save the patient a surgical intervention. A background of MNG and history of radioactive iodine therapy is not uncommon.

Usage of a fixed dose of radioactive iodine for the treatment of hyperthyroidism: one-year outcome in a regional hospital in Hong Kong

OBJECTIVES

To evaluate the efficacy of a fixed dose of radioactive iodine (131-I) in the treatment of thyrotoxicosis, and to identify risk factors associated with treatment failure.

DESIGN

Retrospective study.

SETTING

Thyroid Clinic of a regional hospital in Hong Kong.

PATIENTS

Patients receiving their first dose of radioactive iodine for the treatment of thyrotoxicosis during the inclusive period September 1999 to August 2004.

MAIN OUTCOME MEASURES

Relapse rate and time to relapse.

RESULTS

A total of 113 patients received a fixed dose of 5 mCi (185 MBq), 6 mCi (222 MBq), 8 mCi (296 MBq), and 10 mCi (370 MBq) 131-I in a proportion of 1:6:71:35. At 1 year, 42 (37%) of the patients had relapsed, of which 69% received a second 131-I dose. The median time to relapse after first receiving 131-I was 4 months. At 1 year, the remaining 71 (63%) of the patients were successfully treated; 46 (41%) were euthyroid, and 25 (22%) had became permanently hypothyroid. Basal free thyroxine level and goitre size were significantly associated with a relapse rate after a single dose of 131-I; larger goitres showed a trend towards high rates of relapse. Patients pretreated with propylthiouracil had a higher rate of relapse during the first year after radioactive iodine than those pretreated with carbimazole, but the difference was not significant when combined with other pretreatment variables.

CONCLUSIONS

A single fixed dose of radioactive iodine is a simple, safe, and effective treatment for hyperthyroidism. High basal free thyroxine concentration and large goitre size are associated with higher chance of relapse. Higher radioiodine doses may be considered to improve the cure rate.

Risk of parathyroid adenomas in patients with thyrotoxicosis exposed to radioactive iodine

External ionizing radiation is a risk factor for primary hyperparathyroidism. Whether exposure to radioactive iodine contributes to the risk of primary hyperparathyroidism is unknown. Patients with thyrotoxicosis are often treated with radioactive iodine and its accumulation in the thyroid gland exposes the adjacent parathyroid glands to radioactivity. Six thousand and eighty two patients with thyrotoxicosis (ICD-9 = 242) were identified from medical records. In a randomly selected subcohort we assessed the frequency of treatment with radioactive iodine to be 86%. The number of patient-years at risk was 77,118. Patients with parathyroid adenomas (ICD-9 = 195.1) were recruited from the Swedish Cancer Registry. Eleven patients with parathyroid adenomas following the diagnosis of thyrotoxicosis were identified. The standard incidence ratio (SIR) compared to the reference population of approximately 900,000 was 1.14 (95% CI 0.57-2.03). The median age at exposure was 59 years and the latency period between diagnosis of thyrotoxicosis and parathyroid adenoma was 7.4 years (range <1-19 years). This study does not indicate that patients with thyrotoxicosis treated with radioactive iodine in adult age have increased risk of developing parathyroid adenoma.

Radioactive iodine in thyroid medicine--how it started in Sweden and some of today's challenges

In Sweden, radioactive iodine for thyroid diagnostics and therapy was introduced by Jan Waldenström (1906-1996) and Bengt Skanse (1918-1963). The paper describes the start of the clinical use of radioiodine, the various iodine isotopes available, measurement techniques and dosimetry. There are still problems to solve in relation to an optimal clinical use of radioiodine. One of the remaining challenges is to get consensus about the goal of the treatment of hyperthyreosis, as well as about a method for individual absorbed dose calculations. Careful dose estimates will prevent unnecessary radiation exposure and constitute a base for a future optimised radioiodine therapy. For the dose calculation, it is important to understand if there is any clinically significant temporary reduction in the ability of thyroid tissue to trap or retain 131I-iodide following prior administration of a diagnostic activity of 131I-iodide (stunning of the thyroid). This may be of special concern in connection with treatment of thyroid cancer and its metastases. Finally, the production capacity, availability and delivery of 123I have to be improved to increase clinical access to this radionuclide, which is optimal for diagnostic imaging and which gives lower absorbed dose and therefore also less risk for thyroid stunning than 131I.

Struma ovarii and peritoneal strumosis with thyrotoxicosis

BACKGROUND

Struma ovarii is a highly specialized form of mature ovarian teratoma consisting of thyroid tissue and exhibiting all the histological features of the thyroid gland. Malignant transformation of thyroid tissue in struma ovarii and metastasis are extremely uncommon. In rare cases, benign thyroid tissue may spread to the peritoneal cavity, and pathologic examination of the peritoneal implants shows multiple nodules of varying sizes of mature thyroid tissue similar to struma ovarii. This condition is termed "peritoneal strumosis."

SUMMARY

We report a 49-year-old woman with struma ovarii complicated by peritoneal strumosis with thyrotoxicosis. After surgical resection of the struma ovarii and peritoneal strumosis the patient became euthyroid.

CONCLUSION

To the best of our knowledge this is the first report of a patient with peritoneal strumosis complicated by thyrotoxicosis. The relative contribution to circulating thyroid hormones by the patient's struma ovarii as compared to the peritoneal strumosis is not known.

Radioiodine therapy in patients with amiodarone-induced thyrotoxicosis (AIT)

INTRODUCTION

Amiodarone (AM) is frequently used in the therapy of patients with cardiac disorders. However, due to high iodine content, it has side effects on thyroid function. The use of radioiodine therapy (RIT) in amiodarone-induced thyrotoxicosis (AIT) with low radioactive iodine uptake (RAIU) is still controversial. In these patients therapeutic choices for refractory disease include surgery, antithyroid drugs, or glu ocorticosteriods.

AIM

The aim of the study was to evaluate the efficacy of RIT in patients presenting AIT and low RAIU in two-year follow-up.

PATIENTS AND METHODS

40 patients (25 men and 15 women) aged from 63 to 83 years (x +/- SD: 66.2 +/- 5.0 years; median: 65 years) treated with RIT were included into the study. In these patients AM therapy was essential for the underlying heart disorder, while surgery, antithyroid drugs or glucocorticosteroids, were contraindicated. Forty seven patients with toxic multinodular goiter (TMNG) (39 women and 8 men), matched for age (67 +/- 12 yr; range 54-89 yr), were enrolled into the study as a comparative group. The diagnostic procedures included baseline thyroid function tests (thyrothropin - TSH, free triiodothyronine - fT3 and free thyroxine - fT4 levels), thyroid autoantibodies measurement (antithyroglobulin autoantibodies - TgAb, antithyroid peroxidase autoantibodies - TPOAb, anti-TSH receptor autoantibodies - TRAb), thyroid ultrasonography, thyroid scintiscan and RAIU assessment.

RESULTS

Serum values of TSH, TgAb, TPOAb and TRAb were undetectable in both groups. In patients with AIT fT4 level was 18.7 to 38.7 pmol/l (mean: 27.1 +/- 5.8) and fT3 concentration was 3.9 to 5.6 pmo/l (mean: 5.7 +/- 1.4), while in TMNG patients level of fT4 was 31.5 to 22.2 pmol/l (mean: 25,3 +/- 5,8) and fT3 concentration was 3.8 to 4,2 pmo/l (mean: 4,2 +/- 0,2). Mean RAIU values after 5h and 24h in AIT patients were 2.3 +/- 0.5 and 3.1 +/- 0.9%, while in TMNG patients were 18,0 +/- 3,8 and 35,7 +/- 9,1%, respectively. A significant difference (p<0.001) between 5h and 24h RAIU in AIT compared to TMNG was noted. In all patients with AIT, a dose of 800 MBq of 131I was administered. During two-year-observation recurrence of hyperthyroidism was observed in two patients (5%) with TMNG. These patients received a second radioiodine dose 16.2 +/- 15 months later (the mean re-treatment dose was 735.93 +/- 196.1 MBq). In comparison, none of the patients with AIT required a second 131I dose and only one patient (2.5%) 6 months after ablative 131I dose needed anti-thyroid medication. Transient hypothyroidism was observed in only two patients (5%) with AIH, though was not observed in TMNG. During follow-up time, no sudden deaths in AIT patients were observed; one patient was diagnosed with prostate cancer, and in one patient acute toxic hepatitis after AM occurred.

CONCLUSION

RIT may be a safe and useful method of AIT therapy in patients with low RAIU, in whom other treatment methods are contraindicated.

Thyroid function disorders--Guidelines of the Netherlands Association of Internal Medicine

Thyroid function disorders are common with a female to male ratio of 4 to 1. In adult women primary hypothyroidism and thyrotoxicosis have a prevalence of 3.5/1000 and 0.8/1000, respectively. This guideline is aimed at secondary care providers especially internists, but also contains relevant information for interested general practitioners and gynaecologists. A multidisciplinary working group, containing delegates of professional and patient organisations, prepared the guideline. According to principles of 'evidence-based medicine' available literature was studied and discussed. Considering the availability and quality of published studies a practical advice was formulated. For a full overview of the literature and considerations the reader is referred to the original version of the guideline (accessible through NIV-net). In this manuscript we have aimed to provide the practicing internist with practical and 'as evidence-based as possible' treatment guidelines with respect to thyroid function disorders.

Unexpected dose to the daughter of a patient treated with iodine-131 for hyperthyroidism

Patients treated with radioiodine for thyrotoxicosis and hyperthyroidism are a source of radiation exposure and represent a potential radiation hazard for the people in their environment. Doses to the relatives can be estimated from dose rates of the patient or measured with a proper dosimeter. Sensitive thermoluminescent dosimeters have been used to measure the doses absorbed by the family members of patients treated with iodine-131 ((131)I) for thyrotoxicosis. In the present case, a 12 year old daughter of a female patient, aged 41 years, treated with 592 MBq of (131)I, received a dose of 7.79 mSv during the first seven days. This value is well above the dose constraints proposed by the International Commission on Radiological Protection, i.e 1 mSv for children and fetuses and 3 mSv for carers. Obviously, the patient and her daughter didn't follow the given restrictions. That was unexpected for a 12 year old child who didn't need special care and was able to understand and follow certain instructions. It is the opinion of the authors that if there are children in the family of a hyperthyroid patient treated with (131)I, they should stay in another house for at least a week. If this is impossible for social reasons, hospitalization of the patient should be considered, although treatment of thyrotoxicosis is held in an out-patient basis.

Remission of aplastic anemia induced by treatment for Graves disease in a pediatric patient

Aplastic anemia (AA) is mediated by T-cell autoimmunity in the majority of cases; it is rare and mostly idiopathic in children. We describe a child, who developed AA following Graves' disease which could not be attributed to antithyroid drugs. We hypothesized that both diseases were caused by similar autoimmune process. We monitored the blood counts and did not administer any conventional treatment for AA assuming that the existing anti- hematopoietic stem cell humoral and cellular immunity might subside with induction of remission of Grave's disease. The child went into complete remission with the treatment of the Graves' disease.

Grave's Eye Disease Developing Following Radioiodine Treatment for Toxic Nodular Goitre

The development of Grave's ophthalmopathy (GO) following radioiodine (RI) treatment for Grave's thyrotoxicosis, though controversial, is well described. The development of ophthalmopathy following RI treatment for toxic nodular goitre is much less recognised. We report a 49 year-old female patient who developed thyrotoxicosis and GO after receiving RI treatment for toxic nodular goitre and we also review the relevant literature.

[Thyrotoxicosis revelated by bilateral hip fracture]

Hyperthyroidism is an important cause of secondary osteoporosis and therefore of fractures. Nevertheless, facing an osteoporotic fracture, we do not systematically seek after such thyroid disorder in our daily practice. In this purpose, we report the case of 73 year old women, presented with a bilateral pathological femoral neck fracture. Investigations find a hyperthyroid related osteoporosis. Beyond orthopaedic treatment, radioiodine and bisphosphonate drugs were prescribed.

Release criteria from hospitals of 131I thyrotoxicosis therapy patients in developing countries--case study

The current release limit, recommended by the International Atomic Energy Agency (IAEA)(1), from hospitals of patients undergoing 131I thyrotoxicosis therapy is approximately 1100 MBq (approximately 30 mCi). Owing to the difference in socio-economic conditions, literacy rate, family system, etc., this release limit may not be applicable in most of the developing countries like Pakistan. Therefore, the prime objective of this case study was to re-evaluate the release criteria for 131I thyrotoxicosis therapy patients by taking into account their lifestyle, economic conditions and other facilities such as availability of private/public transport, etc. In this context, systematic studies were carried out and 50 patients (i.e. 35 outpatients and 15 inpatients) at the Nuclear Medicine Oncology and Radiotherapy Institute (NORI), Islamabad, were studied. Exposure rate at the surface of the body and at a distance of 1 m from the standing patient was measured. Results obtained from this study showed that the dose equivalent delivered by these patients to their family members (particularly children) and general public was higher than annual dose limits recommended by the International Commission for Radiation Protection in their report ICRP Publication 60(2). In the light of this study, it is recommended that the release activity limit of approximately 370 MBq (or dose rate level of approximately 10 microSv h-1 at 1 m from the patient) be adopted instead of approximately 1100 MBq in developing countries like Pakistan.

Radiation exposure to family members of patients with thyrotoxicosis treated with iodine-131

PURPOSE

The purpose of this study was twofold: (1) to measure the radiation exposure to family members of out-patients with thyrotoxicosis treated with radioiodine, 131I, using the recommendations from the European Commission (EC) guidance and age-specific periods for behaviour restrictions; (2) to use the results to identify necessary restrictions to ensure recommended dose constraints.

METHODS

The study population comprised 76 family members (46 adults and 30 children below the age of 18) of 42 patients. The patients were treated with an average activity of 417 MBq (range 260-600 MBq). They received oral and written EC recommendations about behaviour restrictions (translated into Norwegian). On the day of treatment we repeated the oral instructions to the patient and an adult family member. The time periods for restrictions were 14 days for children aged 0-10 years, 7 days for persons aged 11-59 years and 3 days for persons aged 60 years and older. Family members wore a thermoluminescent dosimeter (TLD) on each wrist day and night for 2 weeks. The doses received were adjusted to give an estimate of the expected values if the TLDs had been worn indefinitely.

RESULTS

Radiation doses well below the recommended dose constraints were measured for all adult family members and children, except one 2-year-old child; in the latter case the mother probably did not comply with the instructions given.

CONCLUSION

The radiation dose to family members of thyrotoxic patients treated with up to 600 MBq of radioiodine is well below recommended dose constraints if EC instructions are given and compliance is adequate. The duration of restrictions for various age groups used in this study may be considered when establishing guidelines in Norway.

Effect of radioiodine therapy on thyroid nodule size and function in patients with toxic adenomas

BACKGROUND

Autonomously functioning toxic adenomas are a common cause of hyperthyroidism. Although 131I seems to be a good therapeutic option with little postablative hypothyroidism for these patients, only a small number of recent studies have objectively evaluated changes in nodule size by ultrasonography following radioiodine therapy.

METHODS

We prospectively followed 39 patients with a mean age of 51.2 (35-75) years for 12 months and the patients who remained toxic thereafter, until euthyroidism was provided. Thyroid function tests, sonographic volumes were determined initially and 3, 6 and 12 months after treatment. Radioiodine doses of 3.7 MBq.g(-1) thyroid tissue corrected to a 100% 24 h 131I uptake were given. Thirty patients received a single dose, two required two doses and three required three to five doses of 131I due to persistent thyrotoxicosis. Sonographic volumes of the diffuse parts of the glands decreased significantly by 18% from a mean+/-SD value of 50+/-27.6 ml to 41+/-27.4 ml by the end of the 12 months. A significant decrease (8.3%, P=0.002) was achieved in the first three months. Toxic adenomas decreased in size more efficiently (54%) from a mean of 26+/-24 ml to 12+/-10 ml during 12 months, but also most significantly (28.8%, P=0.003) in the first 3 months of the follow-up. Thirty of the patients (76.9%) became euthyroid at the end of 12 months of follow-up. Four patients (10.3%) became overtly hypothyroid during the follow-up.

CONCLUSION

Single or multiple doses of radioiodine can successfully treat toxic adenomas with a low rate of hypothyroidism and considerable nodule-volume reduction.

Treating amiodarone-induced thyrotoxicosis with radioactive iodine

Amiodarone use in the United States is increasing including a role in advanced cardiac life support protocols. There has been a significant increase in hypothyroidism, destructive thyroiditis (type II), and iodine-induced thyrotoxicosis (type I) with amiodarone. Preexisting thyroid disease and status of iodine intake can determine the nature of iodine-induced thyroid disease. Treating amiodarone-induced thyrotoxicosis (AIT) may include traditional antithyroid agents, glucocorticoids, and surgery. Usually, it is assumed the radioactive iodine uptake (RAIU) will be low, and this choice as a treatment modality is excluded at the initial visit. We report a satisfactory outcome in a patient with AIT using radioactive iodine. The role of radioactive iodine in treating AIT is reviewed

Radiation protection recommendations for I-131 thyrotoxicosis, thyroid cancer and phaeochromocytoma patients

Iodine-131 patients pose a radiation risk to their family members, carers and colleagues. Doses from thyrotoxicosis and thyroid cancer patients undergoing standard treatments have been well characterised in the literature. However the resulting precautions cannot be easily adapted to circumstances where the patient has an unusual affliction, or an atypical family or occupational environment. In this study, a model for calculating dose from an I-131 patient is derived from first principles. The model is combined with existing results from the literature to determine a distance weighting factor between patients and family members. This technique reduces the uncertainty in the dose calculations by removing the need to guess the unknown patterns of close contact, a problem common to all previous dose calculation techniques. Data is presented for four unusual I-131 treatments; a child thyroid cancer patient, two thyroid cancer dialysis patients and a phaeochromocytoma patient. The model is used to calculate appropriate periods of restricted contact for these patients. The recommendations provide a useful guide for future unusual I-131 treatments.

Low failure rate of fixed administered activity of 400 MBq 131I with pre-treatment with carbimazole for thyrotoxicosis: the Gateshead Protocol

BACKGROUND

Thyrotoxicosis is associated with significant morbidity, therefore adequate control of the disease is paramount. The outcome of treatment of thyrotoxicosis using radioiodine shows variable failure rates depending, amongst other things, on the administered activity of radioiodine and the use of anti-thyroid drugs. Thus, management should follow an evidence based protocol, which has a low failure rate.

METHOD

We prospectively analysed the outcome of treatment using our Gateshead protocol of a fixed administered activity of radioiodine therapy (400 MBq) given to 201 patients (including 140 with Graves' disease, 48 with toxic multinodular goitre (TMNG) and 13 with toxic nodule) followed up for a median period of 12 months (range, 6-77 months). Carbimazole was discontinued in patients rendered euthyroid 16 days prior to radioiodine. No routine anti-thyroid drugs or thyroxine were given following radioiodine unless hypothyroidism or thyrotoxicosis occurred.

RESULTS

Following the Gateshead protocol led to a failure rate of 6.5% (eight females with Graves' disease, four females with TMNG and one female with toxic nodule), 29% euthyroidism and 64% hypothyroidism. The rates of hypothyroidism for women and for men were: in Graves' disease 77% and 79%, in TMNG 29% and 75%, in toxic nodule 42% and 0%, respectively.

CONCLUSIONS

Our observations show that withholding an antithyroid drug in excess of just over 2 weeks prior to administering a fixed administered activity of radioiodine in patients with thyrotoxicosis leads to the lowest reported failure rate, irrespective of the underlying cause. One possible mechanism for this could be the avoidance of drug induced radio-resistance.

Experience in the use of radioactive iodine therapy for hyperthyroidism in Nigerian patients. A study of twenty-two patients

This is a descriptive and follow-up study of the efficacy of radioiodine (131I) in the treatment of hyperthyroidism in Nigerian patients, and is aimed at creating awareness about the therapy amongst medical practitioners in the West African sub-region. Twenty-two patients (13 female, 9 males) were seen with clinical and biochemical features of thyrotoxicosis, and were treated with 131I between 1991 and 1999. The age range was 31 to 60 years, with a mean age of 44.2 +/- 1.8 years. The indications for 131I therapy were diverse and included its use as a first-line treatment for Graves' disease, thyrotoxic heart disease, recurrent thyrotoxicosis and failed antithyroid drug therapy. An incremental fixed-dose regimen was used in successive years, for different batches of patients. The duration of follow-up ranged from two months to nine years with a mean duration of 3.6 +/- 0.5 years. Three patients achieved euthyroidism, two patients needed a re-treatment with 131I because of persistent Hyperthyroidism. Nine patients developed hypothyroidism between two to 30 months of receiving 131I therapy. While seven other patients defaulted soon after the treatment and one patient who also had type 1 diabetes mellitus suffered a sudden death after two months. In conclusion, our experience revealed similar outcomes as have been reported by other workers. Radioactive iodine was found to be a safe and an effective treatment for hyperthyroidism in Nigerian patients, but a high rate of default precludes adequate long-term follow-up.

Radioiodine therapy in hyperthyroidism: inverse correlation of pretherapeutic iodine uptake level and post-therapeutic outcome

BACKGROUND

High iodine uptake levels are widely accepted as a condition for successful treatment with radioiodine (RAI). However, the existing data are controversial and the correlation of pretherapeutic RAI uptake level and outcome of RAI therapy has not yet been quantified. The aim of this study was to analyze the influence of RAI uptake on the outcome after RAI treatment and to estimate uptake-dependent success rates.

MATERIALS AND METHODS

We retrospectively analyzed 229 patients (m = 53, f = 176; age 64 +/- 14 years) suffering from toxic adenoma, multinodular goitre or Graves' disease, respectively. Clinical status and T3, fT4 and TSH levels were assessed 3, 6, 12 and 18 months after treatment. Successful treatment was defined as loss of hyperthyroidism 18 months after radioiodine therapy. Logistic regression was used to assess the relation between the maximum iodine uptake and the rate of success and hypothyroidism, respectively, after RAI treatment.

RESULTS

Overall, patients presented with pretherapeutic RAI uptake values between 17% and 100%. Eighteen months after RAI treatment, an euthyroid state was achieved in 136 patients (60%), hypothyroidism occurred in 47 patients (20%) and 46 patients (20%) remained hyperthyroid. The patients with the lowest pretherapeutic RAI uptakes showed the highest success rates. The overall success rate significantly decreased from 92% at low RAI uptakes to 57% at high uptakes (P = 0.002). This effect was found in the patients suffering from multinodular goitre as well as in the patients with Graves' disease.

CONCLUSION

In contrast to the current opinion, our results provide evidence that the pretherapeutic iodine uptake level and post-therapeutic outcome are inversely correlated.

Iodine-131 treatment and chromosomal damage: in vivo dose-effect relationship

Although it is well known that radiation induces chromosomal aberrations, there is a lack of information on the in vivo dose-effect relationship in patients receiving iodine-131 treatment, and the results of previous studies are controversial. In this study, the sister chromatid exchange (SCE) method was employed to investigate acute and late chromosomal damage (CD) in the peripheral lymphocytes of 15 patients who received various doses of (131)I (259-3,700 MBq), either for thyrotoxicosis (TTX) or for ablation treatment in differentiated thyroid cancer (DTC). The SCE frequencies in cultured peripheral lymphocytes were determined before treatment (to assess basal SCE frequencies), on the 3rd day (to assess acute SCE frequencies) and 6 months later (to assess late SCE frequencies). The basal, acute and late SCE frequencies (mean+/-SD) were 3.19+/-0.93, 10.83+/-1.72 and 5.75+/-2.06, respectively, in the whole group, and these values differed significantly from each other ( P<0.001). In order to perform a quantitative evaluation of the present data and a comparative analysis with the results of previous studies reported in the literature, we defined acute and late effects using a "damage ratio" (DR) and a "recovery ratio" (RR), based on the basal, acute and late data for individual patients. No statistically significant difference was found in the DR between DTC and TTX patients (76.4%+/-11.5% vs 67.6%+/-9.0%), while the mean RR was higher in TTX patients than in the DTC group (75.2%+/-24.4% vs 36.8%+/-13.7%). The DR on the 3rd day was not related to the administered (131)I dose in the whole group, but a negative correlation was found between the (131)I dose and the RR at the 6th month (r=-0.60, P=0.04). The best fit for this relationship was obtained by a linear-quadratic model, as y=104.89x-28.4x(2)+38.1 ( R(2)=0.51, P=0.04). On the other hand, comparative analysis with the results of previous studies with comparable sampling times revealed that the best fit for the relationships between the administered dose of (131)I and DR and RR were obtained with a linear-quadratic model (Y=alpha D+beta D(2)) rather than a linear one. However, there was an interesting difference in comparison with in vitro studies, in that we found the coefficient beta to have a negative value, suggesting the disappearance of damaged lymphocytes from the peripheral circulation in a dose-dependent manner following (131)I treatment. Further studies are therefore needed to clarify the effect of the negative beta value on the biological dosimetry approach in continuous internal low LET radiation, as in the case of (131)I treatment.

Thyrotoxicosis: a rare presenting symptom of Hurthle cell carcinoma of the thyroid

Hurthle cell carcinoma of the thyroid is a rare type of thyroid neoplasm. The most common clinical presentation is a single palpable thyroid nodule. The neoplasm typically presents as a nonfunctioning or cold nodule on a Tc-99m sodium pertechnetate or radioiodine thyroid scan. We report a case of Hurthle cell carcinoma of the thyroid in a woman presenting with thyrotoxicosis. The Tc-99m thyroid scan was also interesting in that the nodule was a hot or hyperfunctioning area, resulting in a rare scintigraphic finding in a rare tumor. Clinicopathologic aspects and related issues are further discussed.

Recombinant human thyroid-stimulating hormone: pharmacology, clinical applications and potential uses

The major functions of pituitary thyroid-stimulating hormone (TSH) are to maintain the biosynthesis and secretion of the thyroid hormones L-thyroxine (T4) and L-3,5,3'triidothyronine (T3). The TSH core contains two apoproteins, the alpha and beta subunits. The alpha subunit is identical to that of pituitary follitropin, pituitary lutropin and placental chorionic gonadotropin, whereas the beta subunit is unique. TSH is a glycoprotein; the glycoprotein components of the alpha and beta subunits account for more than 10% of their mass and are essential for normal thyrotropic action and intravascular kinetics. The hypothalamic tripeptide, TSH-releasing hormone (TRH) is required for optimum TSH biosynthesis, particularly as far as addition of the glycoprotein components is concerned. TRH deficiency is associated with secretion of TSH molecules that are appropriately measured in most assays but have reduced bioactivity. In previous years the TSH used in clinical practice was obtained and purified from bovine pituitaries. Bovine TSH was used to test thyroid function and to augment the uptake of radioiodine in patients with thyroid cancer. Bovine TSH has been largely abandoned as a clinical agent because of adverse immune reactions. A recombinant human TSH (rhTSH; Thyrogen), has been approved by the US FDA for diagnostic use in patients with thyroid cancer. The alpha and beta subunits of Thyrogen are identical to those of human pituitary TSH. Thyrogen has a specific activity of approximately 4 IU/mg and is a potent stimulator of T4, T3 and thyroglobulin (Tg) secretion in healthy volunteers. It also increases thyroid iodide uptake in patients with thyroid cancer or multinodular goitre and in volunteers, even those exposed to large amounts of stable iodide. Thyroid cancer patients who have been treated by thyroidectomy and radioiodine ablation but are at risk of harbouring residual thyroid cancer are candidates for Thyrogen administration to prepare them for whole body iodide scans and serum Tg measurements. In thyroidectomised thyroid cancer patients who are unable to secrete pituitary TSH upon thyroid hormone withdrawal, Thyrogen is the only acceptable method to prepare them for these procedures. Thyrogen has been used on a compassionate basis to prepare patients for radioiodine ablation. rhTSH, in addition to being useful in the management of patients with thyroid cancer, is potentially useful to test thyroid reserve and to aid in thyroid-related nuclear medicine procedures. In the future, TSH analogues that have superagonist or antagonist properties may become available as therapeutic agents.

The efficacy of low-dose radioactive iodine without a thionamide in the treatment of thyrotoxicosis

Between 1999 and June 2001, 55 unselected thyrotoxic patients were prescribed 200 MBq radioactive iodine (131I). None of these patients received a thionamide such as carbimazole or propylthiouracil within two weeks of treatment or subsequently. Symptom relief was achieved using beta blockers alone. Remission at one year was achieved in 84% of these patients and of these 62% were hypothyroid and taking thyroxine. Within this time, re-treatment of those who remained thyrotoxic achieved an overall success rate at one year of 95%. The outcome of 164 similar patients prescribed 250-400 MBq 131I between 1996 and 2001 gave comparable results. The failure rate after a single 200 MBq 131I dose was significantly lower than that previously published where 185 MBq 131I and thionamides had been used. Our low-dose strategy has the potential for halving the radiation exposure to the patient and the environment, when compared with the ablative strategies in common use.

Radioiodine therapy of thyroid autonomy

Over half a century, treatment of thyroid autonomy with an oral dose of iodine-131 has proven to be effective. The optimum management strategy for the patient is, however, still a matter of debate. The article provides an overview of the pathogenesis of functional autonomy and its clinical relevance. According to the guidelines on both sides of the Atlantic, radioiodine treatment is considered the most comfortable and economical approach to the treatment of the toxic nodular goitre. Some differences in the preparation procedures in the guidelines of the American and the German Society of Nuclear Medicine are discussed with respect to therapy results and the subtypes of thyroid autonomy. The results of studies are summarised concerning changes in thyroid function and thyroid volume after a course of radioiodine treatment. Therapy-related risks, such as immunogenic hypothyroidism or thyroid cancer, are discussed. (131)I treatment of functional autonomy and hyperthyroidism is considered an effective and safe procedure.

Evaluation of dosimetry of radioiodine therapy in benign and malignant thyroid disorders by means of iodine-124 and PET

The aim of this study was to evaluate the use of 124I positron emission tomography (PET) to determine the dosimetry of radioiodine therapy in hyperthyroidism and thyroid cancer. Phantom studies to assess the accuracy of PET were performed using an EEC phantom with spheres of different diameters filled with 3-30 MBq of 124I. Patient dosimetry was derived from PET data obtained 1-13 days after simultaneous oral administration of a therapeutic dose of 131I and a diagnostic dose of 124I. The obtained data were compared with findings from intratherapeutic probe measurements and clinical outcome. The phantom studies confirmed that 124I can be quantitated by PET (imprecision < or =10%), and volumetry is feasible for nodules <13 mm (imprecision < or =20%). Any influence of contamination with 123I or the simultaneous administration of 131I on the accuracy of the PET quantification and the probe measurements was ruled out by phantom measurements with solutions of 131I, 124I and 123I in various ratios. In autonomous nodular goitres, radioiodine uptake measured by PET varied from 25.4% to 64.3% and was not significantly different from that obtained by a scintillation probe (24.1%-73.1%, correlation coefficient r=0.91). Comparison of uptake and effective half-life in normal tissue versus autonomous nodules revealed significant differences in uptake but not in effective half-life [uptake 2.0-8.3 kBq/(ml x MBq) in normal tissue vs 12.6-29.3 kBq/(ml x MBq) in nodules; half-life 97.8-156.7 h in normal tissue vs 73.3-192.3 h in nodules]. Calculated radiation doses ranged between 177 and 633 Gy for autonomous nodules and between 47 and 126 Gy for normal tissue. In thyroid cancer patients, doses between 350 and 1,420 Gy were achieved in thyroid remnants and between 70 and 170 Gy in tumour metastases. It is concluded that 124I and PET are suitable for evaluation of the dosimetry of radioiodine therapy in benign and malignant thyroid diseases. The applied technique might be particularly useful for quantitative dose-response studies in radioiodine treatment and further investigations of stunning phenomena.

Objective estimates of the probability of developing hypothyroidism following radioactive iodine treatment of thyrotoxicosis

OBJECTIVE

Several risk factors have been shown individually to influence the outcome following radioactive iodine (RAI) therapy in the treatment of hyperthyroidism. However, no attempt has been made to determine their independent prognostic values that could be used in a regression model to provide objective estimates of the probability of developing hypothyroidism.

STUDY DESIGN AND METHODS

We audited records of all hyperthyroid patients treated with first dose RAI between 1980 and 1996. Patients were aetiologically categorized into Graves' disease, solitary toxic nodule and toxic multinodular goiter. Following RAI, outcome was categorized as hypothyroidism, euthyroidism and persistent hyperthyroidism. Multiple logistic regression analysis was used to identify significant risk factors, their prognostic values and probability estimates of developing hypothyroidism in the presence of one or more of these factors.

RESULTS

The cumulative incidence of hypothyroidism was 55.8% at 1 year and 86.1% at 10 years. Graves' disease (odds ratio: 4.29), presence of thyroid autoantibodies (odds ratio: 3.51), no antithyroid treatment given prior to RAI (odds ratio: 2.50), non-palpable goiter (odds ratio: 2.48) and high RAI dose (odds ratio: 1.90), were identified as significant independent risk factors. We then developed a predictive table that provides objective estimates of developing hypothyroidism. In the absence of all risk factors we can predict an 11.9% probability of developing hypothyroidism; this increases linearly to a 96.4% probability in the presence of all factors.

CONCLUSIONS

These objective estimates would help in understanding the relative contributions of the known risk factors, and to predict the probability of developing hypothyroidism following RAI treatment. This would not only help patients make an informed consent for a treatment that would lead to life-long replacement therapy but may also prove useful in calculating the RAI dose that may reduce or delay the onset of developing hypothyroidism.

[The management of thyrotoxicosis: a schematic approach]

Thyrotoxicosis is a well defined clinical entity, determined by an increase of plasma levels of thyroid hormones (T3 and T4). A number of causes of thyrotoxicosis are known, and it is therefore very important for the treatment to establish its etiology. In fact, metimazole or propylthiouracil are indicated for the thyrotoxic states caused by thyroid gland's hyperfunction (hyperthyroidism), but are not effective when thyrotoxicosis is determined by a follicular damage and disruption with leakage of preformed thyroid hormones, or in case of thyrotoxicosis factitia. Besides medical therapy, other two therapeutic options are available for the treatment of thyrotoxicosis: radioiodide administration (131I) and surgery. The physician can decide the best therapy on the basis of the following factors: etiology of thyrotoxicosis; patient's age and needs; presence/absence of concomitant diseases or pregnancy; presence of ophthalmopathy; goiter's size; advantages and disadvantages of each therapeutic option. A problem of particular regard is when and if to treat subclinical thyrotoxicosis (low TSH values, and normal plasma levels of thyroid hormones). On the basis of the natural history and of its consequences on the cardiovascular system and skeletal integrity, the authors propose to begin therapy whether subclinical thyrotoxicosis develop in the following four subgroups of subjects: patients with nodular goiter; women in post-menopause; patients with cardiac diseases; patients with osteoporosis.

Translocation frequencies measured in patients one year after radioactive iodine therapy for thyrotoxicosis

PURPOSE

To investigate the incidence of translocations induced by iodine-131 therapy in thyrotoxicosis patients 1 year after the administration of the radiolabelled compound.

MATERIALS AND METHODS

Tricolour FISH with whole-chromosome-specific probes for chromosomes 2, 4 and 8 was used for scoring translocations. From the genomic translocation frequencies, derived using the Lucas formula, equivalent whole-body doses were calculated, based on the in vitro (60)Co gamma-ray dose-response curve.

RESULTS

A total of 101 translocations were observed in 4864 metaphases, 63% being of the two-way type. In the control group used for obtaining dose-response data, nine translocations were observed in 5278 metaphases, 55% being two-way translocations. No correlation was found between the observed frequency of translocations and administered radioactivity. Using the in vitro dose-response, an estimated average dose for the group of nine patients of 0.79 +/- 0.22Gy was obtained. Compared with frequencies following the assumption that the involvement of a particular chromosome in a two-break exchange-type aberration is proportional to its DNA content, chromosome 4 was more frequently involved and chromosomes 2 and 8 less frequently involved in chromosomal rearrangements.

CONCLUSION

This study shows that (131)I therapy for thyrotoxicosis patients induced translocations, especially in chromosome 4, which could be detected 1 year after the administration of the radiolabelled compound.

Characterization of thyroid-stimulating blocking antibodies that appeared during transient hypothyroidism after radioactive iodine therapy

Hypothyroidism after radioactive iodine (RAI) therapy for Graves' disease can be transient or permanent. The cause for early transient hypothyroidism is unknown. We evaluated 11 patients who developed transient hypothyroidism within 6 months of RAI and 12 who remained euthyroid after RAI. Approximately equal numbers of patients in each group had thyroid-stimulating antibody (TSAb) that increased cyclic adenosine monophosphate (cAMP) levels in Chinese hamster ovary (CHO) cells transfected with the recombinant human thyrotropin receptor (TSHR) (WT cells). Approximately equal numbers of patients from both groups had an increase in TSAb activity post-RAI. All TSAbs had their dominant functional epitope on the N-terminus of the TSHR extracellular domain, requiring residues 90-165 for activity because they, but not TSH, completely lost stimulating activity in a receptor chimera, wherein TSHR residues 90-165 were substituted by equivalent residues of the lutropin/choriogonadotropin receptor (LH/CGR). Although equal numbers of patients in both groups had thyrotropin-binding inhibiting immunoglobulin activity (TBII), as measured by radioreceptor assay before RAI, patients with transient hypothyroidism had a surge in TBII activity and all except one became positive for thyroid-stimulating blocking antibodies (TSBAb), as measured by inhibition of TSH-stimulated cAMP from WT cells. When immunoglobulin G (IgGs) were epitope-mapped using TSHR/LH-CGR chimeras with different substitutions, 8 hypothyroid subjects had TSBAbs directed against residues 90-165 of the TSHR, as well as TSHR residues 261-370. Two had functional epitopes directed at residues 9-89 as well as TSHR residues 261-370. None of the euthyroid control patients developed TSBAbs and their TBII activity decreased post-RAI. When patients with transient hypothyroidism reverted to a euthyroid state, TSAb was still detectable in 5; however, TBII was present in all and TSBAb, although decreased, was still positive in 9. In summary, RAI therapy was associated with a change in thyroid antibody characteristics in most patients. Additionally, patients with a surge in TBII and the appearance of TSBAb developed transient hypothyroidism after RAI.