Autonomous Thyroid Research Articles

Treatment of subclinical hyperthyroidism in patients older than 50 years: A randomized controlled study.

Subclinical hyperthyroidism (SCH) is common and associated with atrial fibrillation (AF) risk in the elderly. Current guidelines rely on a low level of evidence. Randomized clinical trial including patients 50 years and older, with TSH <0.4 mU/L and normal thyroid hormone concentrations. All patients showed autonomy on thyroid scan. They were randomized either to receive radioiodine (I131) or to be monitored and treated only if they underwent AF or evolved towards overt hyperthyroidism. Primary outcome was the onset of new AF. Secondary outcomes were treatment-induced hypothyroidism rate and health-related quality of life. 144 patients (mean age 65.3±8.9y, 76% female) were randomized, 74 to surveillance and 70 to treatment. Four patients in the surveillance group and one in the treatment group developed AF (p=0.238). However, the patient who developed AF in the treatment group maintained TSH <0.4 mU/L at AF onset. A post-hoc analysis was carried out and showed that when normalization of TSH was considered, the risk of AF was significantly reduced (p=0.0003). In the surveillance group, several patients showed no classical characteristics associated with AF risk, including age>65y or TSH<0.1mU/L. Of 94 patients treated using radioiodine, 25% developed hypothyroidism during follow-up. Due to recruitment difficulties this study failed to demonstrate that SCH treatment can reduce significantly the incidence of AF in patients older than 50 years with thyroid autonomy even if all the patients who developed AF maintained TSH <0.4 mU/L. This result must be balanced with the increased risk of radioiodine-induced hypothyroidism.

Mathematical Modeling of Free Thyroxine Concentrations During Methimazole Treatment for Graves' Disease: Development and Validation of a Computer-Aided Thyroid Treatment Method.

BackgroundMethimazole (MMI) is the first-line treatment for patients with Graves’ disease (GD). While there are empirical recommendations for initial MMI doses, there is no clear guidance for subsequent MMI dose titrations. We aimed to (a) develop a mathematical model capturing the dynamics of free thyroxine (FT4) during MMI treatment (b), validate this model by use of numerical simulation in comparison with real-life patient data (c), develop the software application Digital Thyroid (DigiThy) serving either as a practice tool for treating virtual patients or as a decision support system with dosing recommendations for MMI, and (d) validate this software framework by comparing the efficacy of its MMI dosing recommendations with that from clinical endocrinologists.MethodsBased on concepts of automatic control and by use of optimization techniques, we developed two first order ordinary differential equations for modeling FT4 dynamics during MMI treatment. Clinical data from patients with GD derived from the outpatient clinic of Endocrinology at the Medical University of Graz, Austria, were used to develop and validate this model. It was subsequently used to create the web-based software application DigiThy as a simulation environment for treating virtual patients and an autonomous computer-aided thyroid treatment (CATT) method providing MMI dosing recommendations.ResultsBased on MMI doses, concentrations of FT4, thyroid-stimulating hormone (TSH), and TSH-receptor antibodies (TRAb), a mathematical model with 8 patient-specific constants was developed. Predicted FT4 concentrations were not significantly different compared to the available consecutively measured FT4 concentrations in 9 patients with GD (52 data pairs, p=0.607). Treatment success of MMI dosing recommendations in 41 virtually generated patients defined by achieved target FT4 concentrations preferably with low required MMI doses was similar between CATT and usual care. Statistically, CATT was significantly superior (p<0.001).ConclusionsOur mathematical model produced valid FT4 predictions during MMI treatment in GD and provided the basis for the DigiThy application already serving as a training tool for treating virtual patients. Clinical trial data are required to evaluate whether DigiThy can be approved as a decision support system with automatically generated MMI dosing recommendations.

Thyroid functional and molecular imaging

Radioiodine uptake (RAIU) test with iodine-123 (Na[123I]I) or iodine-131 (Na[131I]I) enables accurate evaluation and quantification of iodine uptake and kinetics within thyroid cells. Thyroid Scintigraphy (TS) employing Na[123I]I or 99mTc-pertechnetate (Na[99mTc]TcO4) provides information regarding the function and topographical distribution of thyroid cells activity, including detection and localization of ectopic thyroid tissue. Destructive thyrotoxicosis is characterized by low RAIU with scintigraphically reduced radiotracer activity in the thyroid tissue, while productive thyrotoxicosis (i.e. hyperthyroidism “stricto sensu”) is characterized by high RAIU with scintigraphically diffuse (i.e. Graves’ Disease, GD and diffuse thyroid autonomy) or focal (i.e. autonomously functioning thyroid nodules, AFTN) overactivity. Accordingly, RAIU and/or TS are widely used to differentiate different causes of thyrotoxicosis. In addition, several radiopharmaceuticals are also available to help differentiate benign from malignant thyroid nodules and inform clinical decision-making: scintigraphic identification of AFTNs obviate fine-needle aspiration (FNA) biopsy, and [99mTc]Tc-hexakis-(2‑methoxy-2-isobutyl isonitrile ([99mTc]Tc-MIBI) and/or 18F-fluoro-d-glucose ([18F]FDG) may complement the work-up of cytologically indeterminate “cold” nodules for reducing the need for diagnostic lobectomies/thyroidectomies. Finally, RAIU studies are also useful for calculating the administered therapeutic activity of Na[131I]I to treat hyperthyroidism and euthyroid multinodular goiter. All considered, thyroid molecular imaging allows functional characterization of different thyroid diseases, even before clinical symptoms become manifest, and remains integral to the management of such conditions. Our present paper summarizes basic concepts, clinical applications, and potential developments of thyroid molecular imaging in patients affected by thyrotoxicosis and thyroid nodules.

Safety and Effectiveness of Total versus Subtotal Thyroidectomy in Management of Simple Multinodular Goiter

Abstract Background: Disorders of the thyroid gland constitute the second most common endocrine disease following diabetes mellitus. The prevalence of nodular goiter and thyroid auton-omy is increased in regions with chronic Iodine Deficiency (ID). It has been documented that the thyroid gland adjusts to ID in the early stages by diffuse hyperplasia, while chronic exposure to ID results in nodular hyperplasia, increased colloid content and increased height of the follicular cells. Aim of Study: To compare between total and subtotal thyroidectomy in management of Multinodular Goiter as regard safety and effectiveness and post-operative complica-tions like: Hypocalcaemia, recurrent laryngeal nerve injury and hypoparathyroidism. Material and Methods: This prospective study was done at Ain Shams University Hospitals and Banha teaching hospital during the period between March and September 2019. This study included 40 cases of SMNG. Their age was between 30 to 45 years, consent was taken from each patient pre-operatively. Agreement of ethical committee was done. Results: Our study showed the advantages of total thy-roidectomy include adequate eradication of the disease, prevention of recurrent goiter and avoidance of the need for completion surgery in case of occult malignancy, but it is associated with higher morbidity (postoperative thyroidectomy complications: RLN palsy and hypoparathyroidism) and the need for lifelong replacement therapy (L-thyroxin supplemen-tation). Conclusion: In MNG, there are a high percentage of cases with disease involving the entire gland; many areas of appar-ently healthy tissue are found to be microscopically involved with variable grade of chronic lymphocytic thyroiditis or follicular hyperplasia or even lobular dysplasia with tendency to form nodules. These signs of disease of this organ tend to recurrence if not treated.

Molecular Imaging for Thyrotoxicosis and Thyroid Nodules.

After exclusion of exogenous iodine overload, radioiodine uptake (RAIU) testing with 123I or 131I enables the accurate evaluation and quantification of iodine uptake and kinetics within thyroid cells. In addition, scintigraphic evaluation with 123I or 99mTc-pertechnetate (99mTc04-) provides the topographic distribution of thyroid cell activity and allows the detection and localization of ectopic thyroid tissue. Destructive thyrotoxicosis is characterized by abolished or reduced uptake whereas productive thyrotoxicosis (i.e., hyperthyroidism "sensu strictu") is characterized by high RAIU with scintigraphically diffuse (i.e., Graves disease and diffuse thyroid autonomy) or focal (i.e., autonomously functioning thyroid nodules [AFTN]) overactivity. Accordingly, RAIU or thyroid scintigraphy are widely used to differentiate different causes of thyrotoxicosis. In addition, several radiopharmaceuticals are also available to help in differentiating benign from malignant thyroid nodules and inform clinical decision making. In fact, AFTNs can be safely excluded from fine-needle aspiration biopsy while either 99mTc-methoxyisobutylisonitrile (MIBI) and 18F-FDG may complement the work-up of cytologically indeterminate cold nodules and contribute to reducing the need for diagnostic lobectomies/thyroidectomies. Finally, RAIU studies are also useful for calculating the administered therapeutic activity of 131I to treat hyperthyroidism and euthyroid multinodular goiter. All considered, thyroid molecular imaging allows us to characterize molecular/functional aspects of different thyroid diseases, even before clinical symptoms become manifest and remains integral to properly managing such conditions. Our present paper summarizes basic concepts, clinical applications, and potential developments of thyroid molecular imaging in patients affected by thyrotoxicosis and thyroid nodules.

Dosimetry-guided radioiodine therapy of hyperthyroidism: long-term experience and implications for guidelines.

Long-term follow-up after radioactive iodine therapy (RIT) for Graves' disease and toxic thyroid autonomy is incompletely addressed by current guidelines. We retrospectively analyzed the clinical course of 1233 out of 1728 consecutive Graves' disease (n = 536) and thyroid autonomy (n = 1192) patients after dosimetry-guided RIT to optimize follow-up. Patients were referred between 1990 and 2018; follow-up was monitored according to available electronic registers with medical reports, including autopsies from 9 hospitals and 10 residential care homes. In total, 495/1728 cases were censored because of incomplete 6-month follow-up data. The conversion rates to hypothyroidism in Graves' disease and different forms of thyroid autonomy can be deconvoluted into two follow-up periods: first year after RIT and afterward. The conversion rate in Graves' disease was significantly higher than that in all thyroid autonomy subgroups during the first year but almost identical afterwards. Thyroxine substitution started between 10 and 7900 days after RIT at thyroid stimulating hormone between 0.11 and 177 µU/ml. We advise earlier (2-3 weeks) first follow-up checks after RIT in all Graves' disease patients and thyroid autonomy under antithyroid drugs (ATD) and re-checks every 2-4 weeks until conversion to hypothyroidism during the first year. The first check in thyroid autonomy without ATD should be after 3-4 weeks with re-checks every 4-6 weeks. After 1 year, both groups can be re-checked every 4-6 months over the next 5 years. The success rate of RIT in thyroid autonomyincreases with age but the history of RIT is rapidly lost during follow-up.

Thyroid nodules: The Guidelines of the American Thyroid Association from a European Perspective

In Germany and in other regions with former iodine deficiency, thyroid nodules and nodular goiter are still much more frequent than in the U.S.A. The American Thyroid Association (ATA) has published 2015 revised guidelines for patients with thyroid nodules and differentiated thyroid cancer. For evaluation of suspected thyroid nodules the authors describe high, intermediate, low and very low suspicion pattern and recommend further fine needle aspiration cytology, depending on the pattern and the size of the nodule. The high suspicion pattern includes irregular margins of the nodule, which may be an important criterion for malignancy of solitary nodules. In nodular goiters with multiple nodules grown together and without clear margins, frequently observed in former iodine deficiency regions, irregular margins may not be a significant criterion for malignancy. Another pattern, hypoechogenicity, which is frequently seen in benign nodules in former iodine deficiency areas, is also not a clear criterion for malignancy. Only strong hypoechogenicity may indicate malignancy. Another difference relates to the recommendation of scintigraphy that according to the guideline is restricted to patients with decreased TSH. In regions with former iodine deficiency, it has been demonstrated that thyroid autonomy may be present even if TSH is in the lower normal range. Therefore, in Germany scintigraphy is recommended for preoperative evaluation of all patients with thyroid nodules or nodular goiter.

Incidence of thyroid disorders in the second decade of adequate iodine supply in Slovenia.

The incidence of thyroid disorders importantly depends on iodine supply and may change over time. There are only afew data available regarding the change in the incidence of thyroid disorders following the increase in iodine supply. Therefore, the aim of this study was to establish the incidence of thyroid disorders in the second decade of adequate iodine supply in Slovenia. The medical records of 17,828 adult patients who were examined at this department for the first time in the years 2011, 2012, 2013 and 2014 were reviewed. The incidence of diffuse and nodular goiter, thyroid autonomy, Graves' disease, non-hypothyroid and hypothyroid Hashimoto's thyroiditis in the stable catchment area of the University Medical Centre Ljubljana with 1,000,000 inhabitants was followed. Asignificantly lower incidence of thyroid autonomy was observed in the year 2014 as compared to 2011 (p = 0.006), asignificantly higher incidence of Hashimoto's thyroiditis in 2014 as compared to 2013 (p = 0.003), and asignificantly higher incidence of non-hypothyroid Hashimoto's thyroiditis in 2014 as compared to 2011 and 2013 (p = 0.005 and p = 0.022, respectively). The incidence of other thyroid diseases did not change significantly in the observed period. In the second decade of adequate iodine supply in Slovenia, we established asimilar or even alower incidence of most thyroid diseases in the observed 4 years with the exception of Hashimoto's thyroiditis.

Heterogenous biochemical expression of hormone activity in subclinical/overt hyperthyroidism and exogenous thyrotoxicosis

BackgroundSubclinical hyperthyroidism/thyrotoxicosis originates from different causes and clinical conditions, sharing the laboratory constellation of a suppressed TSH in the presence of thyroid hormone concentrations within the reference range. AimPresentation of hyperthyroidism can manifest itself in several ways. We questioned whether there is either a consistent biochemical equivalence of thyroid hormone response to these diagnostic categories, or a high degree of heterogeneity may exist both within and between the different clinical manifestations. MethodsThis secondary analysis of a former prospective cross-sectional trial involved 461 patients with untreated thyroid autonomy, Graves’ disease or on levothyroxine (LT4) after thyroidectomy for thyroid carcinoma. TSH response and biochemical equilibria between TSH and thyroid hormones were contrasted between endogenous hyperthyroidism and thyrotoxicosis (LT4 overdose). ResultsConcentrations of FT4, FT3, TSH, deiodinase activity and BMI differed by diagnostic category. Over various TSH strata, FT4 concentrations were significantly higher in LT4-treated thyroid carcinoma patients, compared to the untreated diseases, though FT3 levels remained comparable. They were concentrated in the upper FT4- but low deiodinase range, distinguishing them from patients with thyroid autonomy and Graves’ disease. In exogenous thyrotoxicosis, TSH and FT3 were less responsive to FT4 concentrations approaching its upper normal/hyperthyroid range. ConclusionsThe presence or lack of TSH feedforward activity determines the system response in the thyroid-active (hyperthyroidism) and no-thyroid response to treatment (thyrotoxicosis). This rules out a consistent thread of thyroid hormone response running through the different diagnostic categories. TSH measurements should therefore be interpreted conditionally and differently in subclinical hyperthyroidism and thyrotoxicosis.

EANM practice guideline/SNMMI procedure standard for RAIU and thyroid scintigraphy.

Scintigraphic evaluation of the thyroid gland enables determination of the iodine-123 iodide or the 99mTc-pertechnetate uptake and distribution and remains the most accurate method for the diagnosis and quantification of thyroid autonomy and the detection of ectopic thyroid tissue. In addition, thyroid scintigraphy and radioiodine uptake test are useful to discriminate hyperthyroidism from destructive thyrotoxicosis and iodine-induced hyperthyroidism, respectively. Several radiopharmaceuticals are available to help in differentiating benign from malignant cytologically indeterminate thyroid nodules and for supporting clinical decision-making. This joint practice guideline/procedure standard from the European Association of Nuclear Medicine (EANM) and the Society of Nuclear Medicine and Molecular Imaging (SNMMI) provides recommendations based on the available evidence in the literature. The purpose of this practice guideline/procedure standard is to assist imaging specialists and clinicians in recommending, performing, and interpreting the results of thyroid scintigraphy (including positron emission tomography) with various radiopharmaceuticals and radioiodine uptake test in patients with different thyroid diseases.

SUN-574 Exogenous Iodine Supplementation-Induced Thyroid Storm in a Patient with Multinodular Goiter

Introduction: Iodine is an essential micronutrient for thyroid hormone synthesis. Its primary source is fortified foods. Supraphysiologic doses of iodine are often found in iodine supplements that are advertised to support thyroid metabolism and reduce goiter size. Normally, excess iodine temporarily inhibits production of thyroid hormone (Wolff-Chaikoff effect), causing goiter and hypothyroidism. In patients with a pre-existing nodular goiter, the auto-regulation of iodine entry into thyroid cells and thyroid hormone synthesis are ineffective. Exposure to high doses of iodine in such cases can precipitate hyperthyroidism (Jod-Basedow phenomenon). Clinical Case: A 50 year-old lady with morbid obesity, chronic lymphedema, longstanding hypothyroidism, and a large retrosternal goiter presented with severe sepsis from cellulitis and tachycardia-induced cardiomyopathy (ejection fraction 30%) from a new-onset atrial flutter with rapid ventricular rate requiring cardioversion. Free (f)T4 was 4.81 ng/dL (0.93-1.7), fT3 6.0 pg/mL (2.0-4.4) and TSH 0.006 mcu/mL (0.27-4.2). Two years ago, she was seen by endocrinology, at which time TSH was 1.58 mcu/mL on desiccated thyroid 30 mg qd. Due to substernal goiter, surgery was recommended then but declined by the patient. Later, she increased desiccated thyroid to 60mg qd and started OTC iodine supplements at 30,000 mcg qd (20,000% RDA) of her own volition, hoping to decrease the size of the goiter. The patient was subsequently lost to follow-up. On this admission, hospital course was complicated by disseminated intravascular coagulation, acute kidney injury needing renal replacement therapy (RRT), encephalopathy, and mechanical ventilation. CT and US demonstrated stable heterogeneous, multinodular goiter (12.5 x 9.3 cm with mediastinal extension), without prominent vascularity. Treatment with PTU, beta-blockers, hydrocortisone, and cholestyramine was initiated on day 1. Serum iodine was markedly elevated at 2,160 ng/ml (40-92) and improved to 221 ng/ml after six days of RRT. Despite PTU 300mg q6h for > 3 weeks, fT4 remained elevated. Eventually fT3 and fT4 normalized to 2.1pg/mL and 1.30ng/dL, respectively, with continued improvement in iodine level. TSH remained undetectable. Severe medical comorbidities precluded surgical resection of the goiter. Conclusion: Dessicated thyroid hormone, markedly supraphysiologic iodine intake, and thyroid autonomy characteristic of MNG contributed to life-threatening thyrotoxicosis in this patient. Extremely high iodine content in the blood and thyroid undoubtedly impeded therapeutic response to PTU, and RRT helped to lower systemic iodine load. This case demonstrates the importance of careful history taking to identify unusual sources of iodine in patients, and patient education regarding possible dangers associated with unregulated OTC and dietary supplements.

Iodinated contrast medium in patients with thyroid disorders

Adequate intake of iodine is essential for normal thyroid function. However, sudden exposure to high amounts of iodine may cause thyroid dysfunction. The aims of this paper are to summarize the literature on the effects of iodinated contrast medium (CM) on thyroid function, the risk to develop CM-induced hyper- and hypothyroidism, and to describe procedures for clinical practice regarding diagnosis, prevention, and treatment of CM-induced hyperthyroidism. The occurrence of CM-induced hyperthyroidism is very rare (<0.5%). In Germany, thyroid function is commonly assessed with laboratory tests (TSH determination) before the use of iodinated CM. Older patients (>60years) with autonomous thyroid and concomitant cardiac diseases are at particular risk of developing hyperthyroidism. The main focus of prevention is to identify patients at risk of developing iodine-induced hyperthyroidism and carry out further thyroid diagnostic procedures prior to CM use. In these patients, prophylaxis with perchlorate and/or thionamides is recommended or alternatively careful monitoring of the patients after use of CM. In patients with overt hyperthyroidism, the use of CM is contraindicated. Iodine-induced hypothyroidism is predominantly found in regions with sufficient iodine supply and in patients with autoimmune thyroiditis. Free iodide influences iodide uptake into the thyroid and therefore interferes with nuclear diagnostic procedures like thyroid scintigraphy as well as radioactive iodine treatment which may be hampered for 2months or longer after use of CM.

Surgery of benign thyroid disease by ENT/head and neck surgeons and general surgeons: 233 cases of vocal fold paralysis in 3509 patients.

Thyroid surgery is mainly performed by general surgeons (GS). The aim of this study is to evaluate the safety and efficiency of thyroid surgery by ENT/head and neck surgeons (ENT), especially regarding the incidence of vocal fold palsy (VFP). We retrospectively analysed 3509 patients (69.0% female) who underwent surgery for benign thyroid diseases (56.8% nodular goitre, 18.6% inactive nodes, 14.0% thyroid autonomy, 7.0% Graves' disease). Operations were mainly performed with intraoperative neuromonitoring by GS (n = 1933) or physicians trained for head and neck surgery (n = 1576). 18.7% of the procedures were carried out by residents in training. VFP occurred in 233 subjects (6.6%); 6.2% in females and 7.6% in males. A lower rate (p < 0.001) was observed in operations performed by ENT (4.7%) than by GS (8.2%). No increased incidence of VFP was seen for surgeries performed by physicians in training (6.2%, n = 657). Prevalence of VFP was not different for minimally invasive (6.3%, n = 950) and conventional surgery (6.8%, n = 2559), but higher in total (7.2%, n = 1916) than in subtotal thyroidectomy (5.0%, n = 997). Postoperative haemorrhage (5.6 vs. 1.9%) and hypocalcaemia < 2.0mmol/l (32.8 vs. 22.0%) were documented more frequently in patients with VFP, also substitution therapy with calcium (23.2 vs. 14.7%) and dihydrotachysterol (8.1 vs. 3.7%) had to be applied more frequently. Thyroid surgery performed by surgeons specifically trained for ENT/head and neck surgery is safe and has a significantly reduced rate of VFP. VFP is associated with other complications (postoperative haemorrhaging, hypocalcaemia).

Amiodarone-induced thyrotoxicosis

Amiodarone-induced thyroid dysfunction occurs in about 15-20% of patients under amiodarone therapy. Amiodarone-induced hypothyroidism (AIH) can develop in patients with an apparently normal thyroid gland or in those with an underlying chronic autoimmune thyroiditis. On a clinical ground, AIH is not challenging and can be easily treated with L-thyroxine therapy. Amiodarone-induced thyrotoxicosis (AIT) can occur in patients with (AIT 1) or without (AIT 2) an underlying thyroid disease. AIT 1 is a true iodine-induced hyperthyroidism occurring in patients with an underlying thyroid autonomy while AIT 2 is a drug-induced destructive thyroiditis. According to the different pathogenetic mechanism, AIT 2 is treated with glucocorticoids while AIT 1 usually responds to thionamides. Thyroidectomy should be considered when AIT represents an imminent risk for cardiac conditions, when patients require a prompt resolution of thyrotoxicosis or when they do not respond to the medical therapy. An effective collaboration between cardiologists and endocrinologists is crucial in each part of the management of AIT patients, including the evaluation of cardiological conditions with regard to thyroid hormone excess and whether, or not, it is necessary to continue amiodarone therapy.

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

Graves' disease (GD) arising after the treatment of toxic multinodular goitre (TMNG) with radioiodine has long been described but it remained unclear whether GD was in fact iodine induced, its incidence, risk factors, natural history and treatment outcomes. A systematic search using The Cochrane Library, Medline and PubMed Central allowed the pooling of data from 3633 patients with thyroid autonomy, 1340 patients with TMNG, to fill gaps in knowledge, regarding the clinical expression of iodine-induced GD (131I-IGD) in adults. 131I-IGD developed in 0-5.3% of those with thyroid autonomy (first year) and in 5-5.4% of those with TMNG, 3-6months after treatment. Patients with toxic adenoma were less affected. 131I-IGD was more common in patients with pre-treatment direct or indirect signs of autoimmunity: positive anti-TPO (p<0.05), glandular hypoechogenicity, TRAbs within reference range, diffuse uptake on 99mTc-pertechnetate scans (p<0.05), findings that may increase the risk tenfold. 131I-IGD manifested 3months after 131I, justifying 15.4-29% of cases of relapse. The rate of spontaneous remission was 17-20% (6months) and the rate of relapse after a second 131I treatment 22-25%. The use of an uptake-based administered 131I activity led to a greater proportion of euthyroid patients (78% compared to 25-50% with the mass-based approach). GD may be triggered by 131I. The incidence of the condition is low. Several risk factors were consistently identified; some have shown to raise the risk significantly. 131I-IGD seems more treatment resistant than iodine-independent GD and the best resolution rates were achieved with uptake-based selected iodine activities.

Reduced radioiodine uptake at increased iodine intake and 131I-induced release of "cold" iodine stored in the thyroid

The extent of urinary iodine excretion (UIE) provides information about iodine supply and release. In the present study we investigated correlations between UIE and radioiodine uptake (RIU) as well as effects of radioiodine therapy on UIE in patients with autonomous goitre. In 197 consecutive patients with thyroid autonomy, UIE was measured twice during radioiodine test (RITe) and correlated with RIU. In 98 of these patients, thyroglobulin and thyroid volume (V) were determined prior to therapy. Individual changes in urinary iodine excretion (DeltaUIE) and TG (DeltaTG) could be investigated four weeks (4W) and six months (6M) after radioiodine therapy. Additionally, DeltaV was determined 6M after therapy. DeltaUIE, DeltaTG and DeltaV were correlated with target dose and target volume. Patients with higher iodine excretion exhibited significantly lower thyroidal radioiodine uptake values. Twofold increased UIE prior to therapy decreased radioiodine uptake by 25%. Compared with pretherapeutic values, UIE and TG were significantly increased four weeks after radioiodine therapy (p < 0.001). Median values of both parameters were found to be doubled. The product of target dose and target volume was not only correlated with a decrease of thyroid volume 6M after therapy, but also with an increase of UIE and TG in the early phase after therapy. It was confirmed that UIE during RITe is a measure for iodine intake and can be used to investigate the competition between stable iodine and radioiodine. The increase of UIE and TG four weeks after therapeutic administration of radioiodine can be explained by disintegrated thyroid follicles. The therapy-induced iodine release may be one important cause for the development of hyperthyroidism in some patients during the first weeks after radioiodine therapy. It may contribute to the known decrease of radioiodine uptake after preapplications of 131I in various thyroid diseases.

Retrospective audit: To investigate the long-term outcome of fixed dose 300 MBq of radioiodine (131-I) treatment for Autonomous Toxic Thyroid Nodule

Retrospective audit: To investigate the long-term outcome of fixed dose 300 MBq of radioiodine (131-I) treatment for Autonomous Toxic Thyroid Nodule

HYPERTHYROIDISM AND ATRIAL FIBRILLATION

Review on a problem of the development of atrial fibrillation in patients with thyrotoxicosis is presented. Thyrotoxicosis is one of the most frequent endocrine diseases, conceding only to a diabetes mellitus. The most frequent reasons of hyperthyroidism are Graves’ disease and functional thyroid autonomy. The authors give an analysis of data on the cardiac effects of thyrotoxicosis, features of heart remodeling under the influence of thyroid hyperfunction, prevalence of atrial fibrillation in thyrotoxicosis, depending on age, as well as the possibility of restoring sinus rhythm in the combination of these diseases. Particular attention is paid to the effect on the heart of subclinical thyrotoxicosis, which is defined as a dysfunction of the thyroid gland, characterized by low serum concentration of thyrotropin, normal values of free thyroxine and free triiodothyronine. Subclinical hyperthyroidism is also capable of causing heart remodeling and diastolic dysfunction. Prevalence of thyrotoxicosis in elderly people is higher in areas of iodine deficiency; it is relevant for our country due to the large territory of iodine deficiency. In elderly patients, the cardiac effects of thyrotoxicosis prevail in the clinical picture, that makes it difficult to diagnose endocrine disorders, and correction of thyrotoxicosis is critically important for the successful control of the heart rhythm. The article also discusses the problem of thyrotoxic cardiomyopathy, caused by the toxic effect of excess thyroid hormones: features of this heart disorder, factors affecting its formation, clinical significance and contribution to the development of rhythm disturbances. The greatest significance is the development of atrial fibrillation as a result of thyrotox-icosis in older patients who already have various cardiovascular diseases. Atrial fibrillation is the most frequent heart rhythm disorder in thyrotoxicosis. The main cause of arrhythmia in hyperthyroidism is the simultaneous existence of frequent focal impulses and circular motions of the excitation wave – the mechanism re-entry. Successful treatment of atrial fibrillation in patients with thyrotoxicosis is possible only when euthyroidism is achieved. In most cases, after the elimination of thyrotoxicosis, a spontaneous restoration of the sinus rhythm is observed. The chances of sinus rhythm restoration are lower in elderly patients with concomitant organic diseases of the myocardium or long-term atrial fibrillation. Moreover, even radically cured thyrotoxicosis leads to deterioration in the life prognosis.

Epidemiological trends of iodine-related thyroid disorders: an example from Slovenia.

The epidemiology of thyroid disorders is significantly associated with iodine supply. In 1999, Slovenia increased iodine content in kitchen salt from 10 mg to 25 mg of potassium iodide per kg of salt. According to the WHO criteria, Slovenia shifted from a mildly iodine-deficient country to a country with adequate iodine intake. Ten years after the increase in iodine intake, the incidence of diffuse goitre and thyroid autonomy decreased. Now patients with diffuse goitre and thyroid autonomy reach older age than the patients before the increase in iodine intake. In addition, patients with thyroid autonomy are less frequently hyperthyroid than ten years ago and iodine-induced hyperthyroidism is less severe. The incidence of highly malignant thyroid carcinoma has also dropped. However, the incidence of Hashimoto's thyroiditis increased, most probably in genetically predisposed individuals. Over the last ten years, many animal and in vitro studies evaluated the effects of endocrine disrupting chemicals (EDC) on various aspects of the thyroid function. They mostly studied the effects of polychlorinated biphenyls (PCBs) and dioxins, brominated flame retardants, phthalates, bisphenol A, perfluorinated chemicals, and perchlorate. However, human studies on the effects of EDCs on the thyroid function are very scarce, especially the long-term ones. What they do suggest is that PCBs and dioxins interfere with the transport of thyroid hormones and adversely affect the thyroid function. Many authors agree that iodine deficiency predisposes the thyroid gland to harmful effects of EDCs. Therefore the effects of EDCs in iodine-deficient areas could be more severe than in areas with adequate iodine intake.

Free thyroxine in needle washout after fine needle aspiration biopsy of toxic thyroid nodules.

The main diagnostic tool for toxic adenomas (TA) is radionuclide imaging indicated in patients with evidence of thyroid nodules in combination with thyrotoxic syndrome. Thyroid ultrasound and fine-needle aspiration biopsy (FNAB) are widely used for the valuation of thyroid masses. There is no literature data concerning the utility of FNAB and related tests for the diagnosis of hyperfunctioning thyroid nodules. The purpose of this study is to determine the levels of free thyroxine (FT4) in the needle washout after FNAB of hot thyroid nodules. The results of our study show that the FT4 levels in needle washout from TA were significantly higher than the surrounding parenchyma and correlated with the hormonal changes in patients with thyroid hyperfunctioning nodules. Further studies on a large number of patients are needed to refine the diagnostic value of this method and evaluate its importance in quantitative risk assessment of thyroid autonomy.