The treatment of hyperthyroidism with iodine-131

Radioactive Iodine Therapy of Graves' Disease in Patients Pretreated With Methimazole Without Radioiodine Uptake for Dose Estimation

OBJECTIVE

To assess response predictors to radioactive iodine (RAI) therapy without using thyroid uptake for dose estimate in patients pretreated with methimazole.

METHODS

Retrospective analysis was performed of patients with Graves' disease treated with RAI doses determined without using uptake studies.

RESULTS

In 242 patients (median age, 41.9 years; 66.1% female), initial mean free thyroxine (FT4) level was 4.7 ng/dL with an estimated thyroid size of 49.15 g. Prior to RAI therapy, average methimazole dose was 22.7 mg/day. Mean RAI dose was 737.0 ±199.4 MBq (19.9 ± 5.4 mCi). Two hundred eight patients (85.9%) responded to RAI therapy; 185 (88.9%) became hypothyroid and 23 (11.1%) became euthyroid. The majority (90.4%) responded within 6 months of therapy with a quicker response (13.9 ± 8.3 vs 17.5 ± 13.5 weeks) for those treated with doses per gram of ≥14.8 MBq (0.4 mCi). Thirty-four nonresponders had a higher initial FT4 level and larger thyroid size with a lower RAI dose per gram of thyroid tissue. In multivariate analysis, the independent response predictor to therapy was dose per gram of thyroid tissue of ≥14.8 MBq (0.4 mCi) (hazard ratio, 3.18; 95% CI, 1.1-9.7). Doses per gram of 14.8 to 18.1 MBq (0.4-0.5 mCi) achieved maximal response rate without added advantage of higher doses. Thyroid size prior to RAI therapy, FT4 levels at diagnosis, and age were inversely related to response.

CONCLUSION

RAI therapy for Graves' disease without uptake studies for dose estimates is an effective treatment method. In patients pretreated with methimazole, an RAI dose per gram of thyroid tissue of ≥14.8 MBq (0.4 mCi) showed high response rate. Prospective studies are needed to confirm the viability of this simplified and cost-effective approach.

A dosing algorithm for individualized radioiodine treatment of cats with hyperthyroidism

BACKGROUND

Radioiodine (¹³¹ I) is the treatment of choice for hyperthyroidism in cats, but current ¹³¹ I-dosing protocols can induce iatrogenic hypothyroidism and expose azotemia.

OBJECTIVES

To develop a cat-specific algorithm to calculate the lowest ¹³¹ I dose to resolve hyperthyroidism, while minimizing risk of iatrogenic hypothyroidism and subsequent azotemia.

ANIMALS

One thousand and four hundred hyperthyroid cats treated with ¹³¹ I.

METHODS

Prospective case series (before-and-after study). All cats had serum concentrations of thyroxine (T₄ ), triiodothyronine (T₃ ), and thyroid-stimulating hormone (TSH) measured (off methimazole ≥1 week). Using thyroid scintigraphy, each cat's thyroid volume and percent uptake of ^99m Tc-pertechnatate (TcTU) were determined. An initial ¹³¹ I dose was calculated by averaging dose scores for T₄ /T₃ concentrations, thyroid volume, and TcTU; 80% of that composite dose was administered. Twenty-four hours later, percent ¹³¹ I uptake was measured, and additional ¹³¹ I administered, as needed, to deliver an adequate radiation dose to the thyroid tumor(s). Serum concentrations of T₄ , TSH, and creatinine were determined 6 to 12 months later.

RESULTS

The median calculated ¹³¹ I dose was 1.9 mCi (range, 1.0-10.6 mCi); 1380 cats required additional ¹³¹ I administration on day 2. Of the cats, 1047 (74.8%) became euthyroid, 57 (4.1%) became overtly hypothyroid, 240 (17.1%) became subclinically hypothyroid, and 56 (4%) remained hyperthyroid. More overtly (71.9%) and subclinically (39.6%) hypothyroid cats developed azotemia than euthyroid cats (14.2%; P < .0001).

CONCLUSIONS AND CLINICAL IMPORTANCE

Our algorithm for calculating individual ¹³¹ I doses resulted in cure rates similar to historical treatment rates, despite much lower ¹³¹ I doses. This algorithm appears to lower prevalence of both ¹³¹ I-induced overt hypothyroidism and azotemia.

The differential diagnosis of central compartment radioactive iodine uptake after thyroidectomy: anatomic and surgical considerations

OBJECTIVE

Foci of increased radioactive iodine (RAI) uptake in the thyroid bed following total thyroidectomy (TT) indicate residual thyroid tissue that may be benign or malignant. The use of postoperative RAI therapy in the form of remnant ablation, adjuvant therapy, or therapeutic intervention is often followed by a posttherapy scan. Our objective is to improve the clinician's understanding of the anatomic complexity of this region and to enhance the interpretation of postoperative scans.

METHODS

We conducted a comprehensive review of the literature evaluating RAI uptake in the central compartment following thyroid cancer treatment and literature related to anatomic nuances associated with this region. Thirty-eight articles were selected.

RESULTS

Through extensive surgical experience and a literature review, we identified the 5 most important anatomic considerations for clinicians to understand in the interpretation of foci of increased RAI uptake in the thyroid bed on a diagnostic scan: 1) residual benign thyroid tissue at the level of the posterior thyroid ligament, 2) residual benign thyroid tissue at the superior portion of the pyramidal lobe and/or superior poles of the lateral thyroid lobes, 3) residual benign thyroid tissue that was left attached to a parathyroid gland in order to preserve its vascularity, 4) ectopic benign thyroid tissue, and 5) malignant thyroid tissue that has metastasized to central compartment nodes or invaded visceral structures.

CONCLUSION

By correlating anatomic description, medical illustrations, surgical photos, and scans, we have attempted to clarify the reasons for foci of increased uptake following TT to improve the clinician's understanding of the anatomic complexity of this region.

Effects of radioiodine administration on serum concentrations of matrix metalloproteinases, adiponectin and thrombospondin-1

Background

In order to assess safety of radioactive iodine administration in the treatment of thyrotoxicosis, we measured concentrations of matrix metalloproteinase-2 (MMP-2), its main inhibitor – TIMP-2 (tissue inhibitor of MMP-2), matrix metalloproteinase-9 (MMP-9), its main inhibitor – TIMP-1, adiponectin, as well as pro-inflammatory and procancerogenic thrombospondin-1 (TSP-1).

Design and patients

The study involved 23 patients treated with radioiodine for thyrotoxicosis. Serum concentrations of TSH, free T4, free T3, MMP-2, MMP-9, TIMP-1, TIMP-2, total adiponectin and TSP-1 were measured by immunoassays just before radioiodine administration (visit 1), and subsequently, after 7 days (visit 2), 3 months (visit 3), 6 to 8 months (visit 4) and 15–18 months after radioiodine administration (visit 5).

Results

There were no acute changes in serum concentrations of MMP-2, MMP-9, TIMP-1, TIMP-2, adiponectin and TSP-1 (visit 1 vs. 2). Subsequently, there was an increase in MMP-2 (from 393±106 ng/ml to 774±424 ng/ml), TIMP-1 (from 177±76 ng/ml to 296±118 ng/ml), and adiponectin (from 16442±9490 ng/ml to 23518±9840 ng/ml), visit 1 to 5, respectively (p < 0.01). Further analysis revealed no significant change in MMP-2/TIMP-2 ratio, but there was a significant decrease in MMP-9/TIMP-1 ratio (p < 0.05), suggestive of possible decrease in free MMP-9 concentrations.

Conclusions

Our data reveal a significant and sustained increase in serum adiponectin, as well as possible decrease of free MMP-9 concentration after radioiodine administration. In contrast, there was no significant change of TSP-1. This might indicate overall safety of radioiodine treatment of thyrotoxicosis in terms of the risks of subsequent cardiovascular and neoplastic disease.

The occurrence of hypothyroidism following radioactive iodine treatment of toxic nodular goiter is related to the TSH level

BACKGROUND

Strategies to increase frequency of euthyroidism following radioactive (RAI) treatment of hyperthyroidism are required.

AIMS

To examine the role of TSH in development of hypothyroidism post RAI treatment in patients with Graves' disease (N = 98) or toxic nodular goiter, TNG (N = 88).

DESIGN

This retrospective study examined thyroid status over a mean of 3.7 years post-RAI.

RESULTS

Although RAI dose was significantly higher in TNG group, hypothyroidism occurred more frequently in Graves' disease (71.4 and 22.7%) P < 0.001. The TSH levels at the time of RAI treatment were lower in TNG patients who remained euthyroid, (0.4+/-0.1 vs. 1.2+/-0.5 mU/l, P < 0.0022).

CONCLUSIONS

A higher frequency of euthyroidism occurs in patients with TNG than with Graves' disease following RAI, particularly when suppressed TSH levels were suppressed at time of RAI-treatment.

Ultrasonography thyroid volume estimation in hyperthyroid patients treated with individual radioiodine dose

Radioiodine (RAI) therapy is a safe and effective treatment for hyperthyroidism and individual doses are frequently administered. Initial thyroid volume (TV) is an important parameter for RAI therapy. Ultrasonography (US) is considered the most reliable method of determining TV. The aim of this study was to evaluate TV by means of US in a cohort of 75 hyperthyroid patients before and after RAI therapy. According to clinical examination, thyroid US and technetium-99m (99mTc)-pernechnetate scintiscan, the diagnosis of hyperthyroidism was multinodular goiter (MNG) in 27, diffuse goiter (DG) in 32 and uninodular goiter (UNG) in 16 patients. The RAI dose to be administered was calculated according to TV and RAI uptake, up to a maximum of 600 MBq. TV was further evaluated 1, 3 and 6-12 months after RAI therapy. The initial TV was 42.3+/-4.0 ml for MNG, 29.7+/-2.8 ml for DG and 34.5+/-3.7 ml for UNG. After 6-12 months a non-significant TV reduction was observed in the MNG group even though the fraction of initial TV was 53.3+/-6.5%. Moreover, a significant TV reduction was noticed in the DG group (8.8+/-2.3 ml; p<0.001). In this group the fraction of initial TV was 28.6+/-3.2% at 6-12 month evaluation. A less marked, though still significant (p=0.04) TV reduction (19.6+/-3.2 ml) was also observed in the UNG group, the fraction of initial TV being 57.8+/-5.3% 6-12 months after RAI. In the whole patient population there was no significant correlation between TV reduction or TV at the last examination and initial TV, RAI dosage, baseline free T4 and TSH levels. No correlation was found between clinical condition at the last examination and TV reduction. In conclusion, these data justify TV estimation by means of US in the protocol of individual RAI dose for the therapy of hyperthyroidism. Our follow-up documents a poorly predictable TV reduction in all clinical conditions, but this is more pronounced and predictable in patients with diffuse toxic goiter.

Variability of the administered radioiodine doses for the treatment of hyperthyroidism in Belgium

OBJECTIVE

When using radioiodine for hyperthyroidism there is no consensus regarding the administration of fixed or calculated doses. Guidelines do not specify the preferable approach or the parameters to use to calculate the dose. Therefore, the dose might be quite different with regard to the chosen procedure. This study was undertaken to evaluate the variability of the amount of radioiodine administered in Belgium in various cases of hyperthyroidism.

DESIGN AND PATIENTS

Twenty-one Belgian nuclear medicine physicians received summarized clinical files from 10 patients suffering from overt hyperthyroidism (n = 7) or subclinical hyperthyroidism (n = 3). Five patients had homogeneous goiters, one had multinodular goiter, and four had hot nodule. Participants had to determine the radioiodine dose (millicuries, mCi) they would give in each case.

RESULTS

Proposed doses varied between 2 mCi and 25 mCi. Mean proposed dose for nodular disease was 10.71 mCi; it was 6.79 mCi for homogeneous goiter. For individual cases, a difference between the lowest and the highest dose of more than 17 mCi was observed in more than 50% of the cases.

CONCLUSIONS

We believe that more precise guidelines are mandatory, underlying uncertainties, controversies but recommending however, as minimal and maximal doses to administer, as well as clinical and biological parameters, if any, to be taken into account in order to modulate these doses.

Optimized radioiodine therapy for Graves?? disease: Two MIRD-based models for the computation of patient-specific therapeutic 131I activity

AIM

(131)I therapy is increasingly used for Graves' hyperthyroidism. Debate remains about the best method for calculating the activity to administer, as well as about the potential benefit of such computed activity. Several arguments plead, nevertheless, in favour of a personalized computation, such as inter-individual variations of thyroid volume and biokinetics.

METHODS

A MIRD-based dosimetric approach, with an additional extension that takes into account the variation of thyroid mass during the treatment, has been developed. This approach includes the benefits of a personalized determination of biokinetics. Results were compared with those of six methods widely used in routine practice. Forty-one patients were enrolled (34 women, seven men; mean age +/-SD: 48.11 +/- 6.4 years). (131)I uptakes were measured at 4, 24 and 96 h (36.2 +/- 14.6%, 42.8 +/- 9.7% and 27.6 +/- 6.8%, respectively), following administration of the tracer. The kinetics of iodine in the thyroid were evaluated using a two-compartment model (effective half-life of 5.1 +/- 1.6 days). Computations of activities to deliver the doses prescribed by the physician were done with the eight formalisms.

RESULTS

There was no statistical difference between results of the two MIRD-based formalisms (227 +/- 148 MBq and 213 +/- 124 MBq), which were also not significantly different from those obtained with the majority of the other methods (from 128 +/- 95 MBq to 275 +/- 223 MBq). However, a large intra-individual difference up to a factor of 2 between two given methods was found.

CONCLUSION

The formalism developed appears to be a good compromise between all the common formalisms already used in many institutions. Furthermore, it allows the exposures of target volumes and non-target volumes to be planned individually and practical individual radiation protection recommendations to be implemented.

Three basic patterns of changes in serum thyroid hormone levels in Graves' disease during the one-year period after radioiodine therapy

The purpose of this study was to clarify the characteristic patterns of the thyroid hormonal changes in Graves' disease during the one-year period after 131I therapy considering that few serial hormonal data during this period are available in the literature.

METHODS

The levels of serum T3, T4 and FT4 before and during one year were plotted as a function of time in 70 therapy courses of 58 patients without subsequent antithyroid or steroid therapy.

RESULTS

35 euthyroid, 6 hypothyroid and 29 hyperthyroid states were obtained during one year after therapy. Although individual patients had individual hormonal changing patterns, 3 common basic patterns were observed from baseline to one month (early) and thereafter (late), respectively. The early patterns were a decrease in 54 (77%), a minimum change in 8 (11.5%) and an increase in 8 (11.5%). The late patterns were a stable state after an initial decrease with a bottom followed by an increase (valley pattern) in 47 (67%), a stable state after an initial increase with a peak followed by a decrease with a bottom and a subsequent re-increase (mountain pattern) in 12 (17%) and a late stable state after a gradual slow decrease without an obvious bottom near or till one year (downhill pattern) in 11 (16%). The bottom level and the degree of hormonal recovery from the bottom determined the stable euthyroid, hypothyroid or hyperthyroid state in 49 (86%) of 57 with the valley or mountain pattern. Most of the bottom levels (81%) and transient abnormal changes including transient hypothyroidism (93%, 13/14), peak or hyperthyroidism (85%, 11/13) and euthyroidism (67%, 10/15) appeared within 6 months. The post-therapeutic stable euthyroid, hypothyroid or hyperthyroid state could be judged from the hormonal patterns in 57% (39/68) from 2.5 to 6 months, in 18% (12/68) from 6 to 9 months and in 25% (17/68) thereafter.

CONCLUSION

Although the changes in thyroid hormones are not constant in Graves' disease during one year after 131I therapy, there are three basic patterns; valley, mountain and downhill patterns from one month after therapy. The post-therapeutic stable state can be judged by the hormonal level recovered from the bottom in most patients.

Graves disease in childhood: a review of the options for diagnosis and treatment

While diagnosing Graves disease in childhood and adolescence does not usually present specific problems, the treatment of hyperthyroidism is still controversial. In particular, with regard to the use of radioiodine therapy, strategies vary between many European and North American pediatric endocrinology centers. After the diagnosis is made, antithyroid drug treatment with methimazole (thiamazole), carbimazole, or propylthiouracil should be performed with caution, in particular, because of severe adverse effects, such as agranulocytosis or hepatitis, that are found in up to 1% of patients. Antithyroid drug treatment should not be continued long-term, particularly since definitive remission cannot be expected in more than 30-40% of patients. In contrast, the risk of severe adverse effects is still present, and the risk of thyroid carcinoma increases with time and appears to be considerably higher than after radioiodine treatment. To a great extent, the success of surgery depends on the skills of a trained surgeon. The question of whether to perform total or subtotal thyroidectomy is yet to be resolved. Surgery should be considered in patients with a large thyroid gland (>80g), severe ophthalmopathy, and a lack of remission on antithyroid drug treatment. Success rates have increased to up to 97%, while severe adverse effects (laryngeal nerve palsy, hypoparathyroidism) occur in approximately 4% of patients. Mortality is below 0.1%. Radioiodine treatment in children >5 years of age does not appear to be associated with an increased risk of thyroid carcinoma; however, long-term data are lacking. Compared with the surgical approach, success rates are lower, particularly if low doses of radioiodine are used. In general, adverse effects are less prevalent than in patients who have undergone surgery.

Track structures and dose distributions from decays of (131)I and (125)I in and around water spheres simulating micrometastases of differentiated thyroid cancer

The disintegration of the radionuclides (131)I and (125)I and the subsequent charged-particle tracks left behind in water (as a model substance for a biological cell) are simulated by the Monte Carlo track structure simulation code PARTRAC, using new inelastic electron scattering cross sections for condensed water. Every photon and electron emitted was followed in detail, event by event, down to 10 eV. From the spatial information on the track structures, absorbed dose distributions per (131)I and (125)I decay were calculated in and around water spheres simulating micrometastases as well as in the tissue surrounding such metastases. These radionuclides were assumed to be distributed uniformly inside spheres of different diameters (0.01, 0.03, 0.1, 0.3, 1.0 and 3.0 mm). The respective electron degradation spectra, the nearest-neighbor distance distributions between inelastic events, and the distance distributions for all activations for both iodine radionuclides were calculated. The absorbed fractions of the initial electron energies, absorbed doses and energy depositions, and single-event distributions, F(1)(epsilon), inside the six water spheres described above and in the surrounding tissue were also calculated. The absorbed doses per decay inside the six water spheres, i.e., the calculated S values (listed from 0.01 to 3.0 mm), were 6.8 x 10(-4), 7.2 x 10(-5), 5.5 x 10(-6), 4.9 x 10(-7), 3.1 x 10(-8) and 1.8 x 10(-9) Gy Bq(-1) s(-1) for (131)I, and 3.4 x 10(-3), 1.7 x 10(-4), 5.1 x 10(-6), 2.0 x 10(-7), 5.6 x 10(-9) and 2.2 x 10(-10) Gy Bq(-1) s(-1) for (125)I. It is concluded that, in the treatment of thyroid cancer, the geometrical track structure properties of (125)I might be superior to those of (131)I in micrometastases with diameters less than 0.1 mm; however, in this medical context, many other factors also have to be considered.

The effect of antithyroid drug pretreatment on acute changes in thyroid hormone levels after (131)I ablation for Graves' disease

Acute changes in thyroid hormone levels before and after radioiodine therapy for Graves' disease were compared in 42 patients randomized to receive either antithyroid drug pretreatment or no pretreatment. Five patients (11.9%), including 3 in the pretreatment arm and 2 in the no pretreatment arm experienced a late exacerbation of thyrotoxicosis after radioiodine therapy. The majority (19 of 21, 90.5%) of pretreated patients experienced a transient increase in free T(4) and free T(3) after discontinuation of antithyroid drugs, with little further elevation after radioiodine therapy. After stopping antithyroid drugs and before radioiodine administration, mean serum free T(4) values rose from 14.7 +/- 6.9 to 21.6 +/- 12.1 pmol/L, representing a 46.9% increase, whereas serum free T(3) levels rose from 4.9 +/- 1.7 to 8.1 +/- 6.3 pmol/L, representing a 65.3% increase. The average pretreated patient experienced a 52.4% increase [95% confidence interval (CI), +26.4% to +78.5%] in free T(4) and a 61.8% increase (95% CI, +23.5% to +100.0%) in free T(3). Conversely, the majority (19 of 21, 90.5%) of nonpretreated patients experienced a rapid decline in thyroid hormone levels after radioiodine treatment. Over the 14 days after radioiodine therapy mean free T(4) values in nonpretreated patients fell from 85.8 +/- 60.4 to 58.0 +/- 76.5 pmol/L, representing a 32.4% decrease, whereas mean free T(3) levels fell from 16.1 +/- 8.0 to 10.8 +/- 11.1 pmol/L, representing a 32.9% decrease. The average nonpretreated patient experienced a 20.6% decrease (95% CI, -47.3% to +7.0%) in free T(4) and a 24.3% decrease (95% CI, -1.2% to -47.4%) in free T(3) during this time period. Excluding 2 patients with a late exacerbation after radioiodine, 19 nonpretreated patients experienced a decrease in mean free T(4) values from 76.8 +/- 46.6 to 36.6 +/- 19.8 pmol/L, representing a 52.3% decrease, whereas mean free T(3) levels fell from 15.5 +/- 7.7 to 7.8 +/- 3.6 pmol/L, representing a 49.7% decrease. The average decrease in free T(4) levels among this subgroup of patients was 30.1% (95% CI, -4.6% to -55.6%), whereas the average decrease in free T(3) was 34.4% (95% CI, -13.7% to -55.1%). High levels of TSH receptor autoantibodies at diagnosis were associated with an acute worsening of thyrotoxicosis after stopping antithyroid drug pretreatment. We conclude that pretreatment with antithyroid drugs does not protect against worsening thyrotoxicosis after radioiodine, but may allow such patients to start from a lower baseline level should an aggravation in thyrotoxicosis occur. The findings support the recommendation that most patients with Graves' disease do not require antithyroid drug pretreatment before receiving radioiodine.

Timing for repeated treatment of hyperthyroid disease with radioactive iodine after initial treatment failure

PURPOSE

It has been reported that the effect of radioactive iodine (RAI) treatment is complete in 4 to 6 months. This retrospective study evaluated the appropriate time for repeated treatment of hyperthyroid disease with RAI after initial treatment failure.

METHODS

Outcomes of 128 patients treated with RAI for hyperthyroid disease were reviewed retrospectively at 3 and 6 months.

RESULTS

Eighty patients (group A) were treated successfully with a single dose of RAI. Twenty patients (group B) required a second treatment dose. Twenty-eight patients were lost to follow-up. All patients in group A were clinically improved to various degrees at 3 months and continued to improve at 6 months. All eight patients in group B who showed no improvement at 3 months remained the same at 6 months. The difference between the two groups was statistically significant.

CONCLUSION

Patients with hyperthyroid disease who are unimproved at 3 months can be retreated with RAI without further delay.

Cytologic changes induced by 131I in the thyroid glands of patients with hyperthyroidism; results of fine needle aspiration cytology

Cytological changes in the thyroid glands of 120 patients who had received 131I treatment for hyperthyroidism were examined in detail. The cytological material was obtained by fine needle aspiration cytology. The patients were divided into four groups according to the amount of time elapsed after the 131I treatment. The control groups were selected from euthyroid patients with hypoactive or non-functional solitary nodules and patients with Graves' disease who had not received 131I therapy. The thyrocytes revealed degenerative changes in the immediate period after cessation of treatment. One year after the treatment some non-specific changes, such as oxyphilic metaplasia and regeneration, were seen. No malignant change has been observed clinically or cytologically during up to 20 years of follow up since receiving 131I.

Designing an optimal experiment for Bayesian estimation: application to the kinetics of iodine thyroid uptake

We consider the problem of designing an optimal experiment for Bayesian estimation of the parameters of a non-linear model. When their distribution is known, the Bayesian approach allows individual estimation from a small number of measurements; the design determines the accuracy of the estimates. We propose to optimize this design by maximizing a general criterion: the expectation of the information supplied by the experiment. This approach is applied to optimize the two sampling times for Bayesian estimation of the kinetics of radioiodine thyroid uptake from an estimated non-parametric prior distribution.

Superior vena cava syndrome and tracheal obstruction due to multinodular goiter

Tracheal obstruction and superior vena cava (SVC) syndrome are rare complications of retrosternal goiter. These two conditions present a difficult diagnostic and therapeutic challenge. Malignancy is the most common cause of SVC syndrome. Determining whether SVC syndrome is due to a benign or malignant process is imperative before instituting treatment, but this determination may be difficult. We present a case of a patient presenting with upper airway obstruction and SVC syndrome with a large mediastinal mass. The mass was determined to be a multinodular goiter. The patient was managed by surgical removal of the goiter with complete resolution of symptoms. This case illustrates the need for careful preoperative evaluation and the importance of establishing a histologic diagnosis prior to initiating treatment for SVC syndrome.

Computer-assisted individual estimation of radioiodine thyroid uptake in Grave's disease

A computer-assisted Bayesian individual estimation of radioiodine thyroid uptake kinetics for patients suffering from Grave's disease is proposed. The program provides a fast computation of the activity to be administered to a given patient to achieve a target thyroid absorbed dose. This determination relies upon the patient biological covariates and upon a small number of measurements performed during a preliminar kinetic study of radioiodine thyroid uptake. Our results indicate that a two-sample Bayesian approach is reliable when external thyroid counts are performed at 2 h and 168 h after a test dose and has advantages over conventional kinetic experiments in terms of patient acceptability. This method is implemented on widespread computers and interfaced with a patient database. An interactive user interface with in-line data checking is provided. The program could be also a tool to better study the relationship between the absorbed dose and the clinical effect.

A reappraisal of the role of methimazole and other factors on the efficacy and outcome of radioiodine therapy of Graves' hyperthyroidism

The outcome of radioiodine therapy of Graves' hyperthyroidism was retrospectively evaluated in 274 consecutive patients treated from 1975 to 1984. At 1-yr follow-up, permanent hypothyroidism occurred in 36.9% of patients and the cumulative incidence of hypothyroidism progressively increased up to 79.3% after 7-10 yr. At the end of the follow-up period, 148 patients (54%) were hypothyroid, 115 (42%) euthyroid and 11 (4%) still hyperthyroid. The prevalence of hypothyroidism was significantly higher in patients with small goiters (less than or equal to 50 g) than in those with large goiters (greater than 90 g). Moreover, hypothyroidism was more frequent in patients with high thyroglobulin antibodies titers (greater than or equal to 1:25,600) than in those with low titers or negative tests, and occurred earlier in the former group than in the latter ones Correction of thyrotoxicosis was obtained after the administration of a single dose of 131I in 187 patients (63.6%); 69 patients required two doses and 11 three or more doses. Seven patients refused further treatment with 131I after the first dose. In an effort to identify possible factors affecting the efficacy of 131I therapy, we evaluated the results obtained after the administration of the first dose of radioiodine. We found that large goiters, rapid iodide turnover and adjunctive therapy with methimazole shortly after radioiodine were associated with a higher rate of persistence of thyrotoxicosis, whereas an increased prevalence of hypothyroidism was observed in patients with small goiters and in those not treated with methimazole up to one week after 131I.(ABSTRACT TRUNCATED AT 250 WORDS)

Surgical treatment of Graves' disease

Seven men and 81 women were operated on for Graves' disease. Their median age was 33 years. Eleven patients underwent a bilateral subtotal lobectomy; 77 patients underwent a complete lobectomy with contralateral partial lobectomy. Forty-seven patients were treated before 1981. In these patients, the weight of the thyroid remnant was estimated empirically between 5 and 12 g. In the 41 patients treated since 1981, the remnant weight was estimated at 5 g by comparative weighing. There were no postoperative deaths. Functional results were established in 83 patients with an average follow-up of 50 months (range 12 to 156 months), with control of vocal cord mobility demonstrated by indirect laryngoscopy in 66 patients. Hormonal determinations were carried out in 74 patients. There were no cases of permanent hypoparathyroidism. Three patients (4.5 percent) had unilateral vocal cord dysfunction. Twelve patients (14.5 percent) had clinical and biologic hypothyroidism, which occurred within 1 year postoperatively in 11 cases. Seven patients (8.3 percent) had latent hypothyroidism only discovered by hormonal determinations. Fifteen patients (17.8 percent) had recurrent hyperthyroidism, 6 of whom were diagnosed by hormonal determinations. The actuarial recurrence rate increased progressively up to the sixth postoperative year. The only predictive factor for recurrence was the type of operation. Patients who underwent a bilateral subtotal lobectomy had more recurrences than patients who underwent a complete lobectomy with partial contralateral lobectomy (p less than 0.01). These results suggest that patients should be followed closely for many years and should undergo hormonal determinations regularly, as some recurrences can occur 5 years or more after operation with very few symptoms.

Low-dose 131I in treatment of Graves' disease

One hundred and sixty-four patients with Graves' disease were treated with low-dose radioiodine (2 mCi), with a mean follow up of 4 1/2 years. At this time 74 (45%) were euthyroid having had a single dose, with a total of 131 (80%) being controlled with one or more doses. Three (2%) were still toxic but their mean follow up was only 3 years. Thirty (18%) were rendered hypothyroid, two-thirds of these after a single dose of 2 mCi 131I. The one-year incidence of hypothyroidism was 6%, with an incidence at 6 years of 20%. Previous surgery, medical treatment and thyroid antibody status appeared to have no influence on the outcome.

Effect of pretreatment with carbimazole on early outcome following radio-iodine (131I) therapy

Of a group of 55 thyrotoxic patients given therapeutic radio-iodine (131I), 24 were made euthyroid with carbimazole before 131I: the remainder were given 131I alone. Carbimazole was discontinued 5 days before 131I was administered. By 3 months after 131I treatment there was a greater incidence of hypothyroidism in the group given 131I alone (42% vs 25%), but a lower incidence of persistent thyrotoxicosis (16% vs 46%), (P less than 0.05). One year after treatment a similar proportion of each group had persistent thyrotoxicosis (21% vs 23%), but there remained a lower incidence of hypothyroidism in the group pretreated with carbimazole (25% vs 45%). It is suggested that pretreatment with carbimazole reduces the degree of radiation induced thyroid damage.

Transient hypothyroidism following radioiodine therapy for thyrotoxicosis

A prospective study of thyroid function including serial tracer radioisotope uptake measurements in 55 patients treated with 131I therapy is described. Five patients had an episode of transient hypothyroidism within eight months of treatment: in three of these patients this was due to impaired organification of iodide, with normal iodide trapping by the thyroid (as measured by a twenty minute 123I uptake) being preserved. In contrast, in all patients who developed permanent hypothyroidism, iodide trapping was markedly diminished and did not recover. It is suggested that hypothyroidism due to organification failure following 131I therapy is potentially short-lived; where hypothyroidism is associated with gross impairment of iodide trapping, recovery is unlikely. Early iodine uptake measurements may be of value in selecting those patients whose hypothyroidism is transient and who do not require permanent thyroid hormone replacement.

Cure rate after 131I therapy for hyperthyroidism

The cure rate of hyperthyroidism after 131I therapy was analysed in 4 473 patients, aged between 14 and 91 years, treated between 1951 and 1975. Despite unchanged treatment principles, the cumulative incidence of cure increased for each 5-year period. Within the first 4 months 34 per cent of the patients with diffuse thyroid glands treated during 1951-1955 were cured, as compared with 59 per cent of those treated 1971-1975, i.e. an increment by a factor of 1.7. The corresponding figures for patients with nodular thyroid glands were 23 and 54 per cent, respectively, or a factor of 2.3.

The early follow-up of 131I-treatment of thyrotoxicosis

No general agreement exists concerning the optimal time for the first control of patients treated with 131I for thyrotoxicosis. Ten consecutive cases were followed clinically, and current laboratory thyroid tests were frequntly performed during a 14 week period to point out the optimal control time and the best setup of control parameters for such patients. It is concluded that clinical examination, supplied with T4, T3, T3-test, and TSH determinations 12--14 weeks after therapy seems rational as a first step in the lifelong follow-up of these patients.