Diagnosis and management of amiodarone-induced thyrotoxicosis in Europe: results of an international survey among members of the European Thyroid Association

Toenail and blood selenium mediated regulation of thyroid dysfunction through immune cells: a mediation Mendelian randomization analysis

Purpose

Specific nutrients found in food, such as minerals, antioxidants, and macronutrients, have a significant impact on immune function and human health. However, there is currently limited research exploring the relationship between specific nutrients, immune system function, and thyroid dysfunction commonly observed in autoimmune thyroid diseases, which manifest predominantly as hyperthyroidism or hypothyroidism. Therefore, the objective of this study was to investigate the connections between dietary traits and thyroid dysfunction, as well as the potential mediating role of immune cells, using Mendelian randomization (MR) analysis.

Methods

The two-step MR analysis used single-nucleotide polymorphisms as instruments, with a threshold of p < 5e-08 for nutrients and thyroid dysfunction, and p < 5e-06 for immune cells. Data from different GWAS databases and UK Biobank were combined to analyze 8 antioxidants and 7 minerals, while the data for 4 macronutrients came from a cohort of 235,000 individuals of European. The outcome data (hypothyroidism, N = 3340; hyperthyroidism, N = 1840; free thyroxin [FT4], N = 49,269; thyroid-stimulating hormone [TSH], N = 54,288) were source from the ThyroidOmics consortium. Immune trait data, including 731 immune phenotypes, were collected from the GWAS catalog.

Results

The results revealed that nutrient changes, such as lycopene, toenail and blood selenium, and α-tocopherol, impacted the immune system. Immune cells also affected thyroid function, with cDC cells promoting hypothyroidism and median fluorescence intensity (MFI) phenotypes correlating strongly with FT4 levels. Toenail and blood selenium reduce the relative cell counts (RCC) phenotypes of immune cells (CD62L- plasmacytoid DC %DC and transitional B cells %Lymphocyte), thereby diminishing its promoting effect on hypothyroidis. Furthermore, toenail and blood selenium mainly impacted phenotypes in three types of T cells (CD25 + ⁣ + CD8br, CD3 on CD45RA- CD4+, and CD45RA on Terminally Differentiated CD8br), reinforcing the negative regulation of FT4 levels.

Conclusion

The role of immune cells as mediators in the relationship between nutrients and thyroid dysfunction highlights their potential as diagnostic or therapeutic markers. Toenail and blood selenium levels can indirectly impact hypothyroidism by influencing the RCC levels of two types of immune cells, and can indirectly affect FT4 levels by influencing three types of T cells.

Cardiac evaluation in amiodarone-induced thyroid dysfunction with suspected cardiac ischemia?: a case report and review of the literature

BACKGROUND

Amiodarone-induced thyroid dysfunction (AIT) is a side-effect associated with the use of Amiodarone for the treatment of refractory arrythmias. Resulting hyperthyroidism can precipitate cardiac complications, including cardiac ischemia and myocardial infarction, although this has only been described in a few case reports.

CASE PRESENTATION

We present here a clinical scenario involving a 66-year-old male Caucasian patient under Amiodarone for atrial fibrillation, who developed AIT. In the presence of dyspnea, multiple cardiovascular risk factors and ECG abnormalities, a transthoracic echocardiogram was performed, showing inferobasal hypokinesia. This led to further investigations through a cardiac PET-CT, where cardiac ischemia was suspected. Ultimately, the coronary angiography revealed no abnormalities. Nonetheless, these extensive cardiologic investigations led to a delay in initiating an emergency endovascular revascularization for acute-on-chronic left limb ischemia. Although initial treatment using Carbimazole was not successful after three weeks, the patient reached euthyroidism after completion of the treatment with Prednisone so that eventually thyroidectomy was not performed. Endovascular revascularization was finally performed after more than one month.

CONCLUSIONS

We discuss here cardiac abnormalities in patients with AIT, which may be due to relative ischemia secondary to increased metabolic demand during hyperthyroidism. Improvement of cardiac complications is expected through an optimal AIT therapy including medical therapy as the primary approach and, when necessary, thyroidectomy. Cardiac investigations in the context of AIT should be carefully considered and may not justify delaying other crucial interventions. If considered mandatory, diagnostic procedures such as coronary angiography should be preferred to functional testing.

Short review: novel concepts in the approach to patients with amiodarone-induced thyrotoxicosis

INTRODUCTION

Amiodarone-induced thyrotoxicosis is associated with high morbidity and mortality rates. The approach to this condition is widely variable across different medical specialists and even among expert endocrinologists. As a matter of fact, the approach to amiodarone-induced thyrotoxicosis has always been considered difficult, due to diagnostic uncertainties easily resulting in missteps, and therapeutic challenges easily resulting in unresponsiveness or slow-responsiveness to the administered drugs.

PURPOSE

Our purpose is to review novelties emerged during the last years about this condition, with the aim to provide novel insights on the diagnostic and therapeutic management of this challenging condition.

Amiodarone-Induced Myxedema Coma in Elderly Patients: A Systematic Review of Case Reports

This systematic review aimed to explore whether elderly patients administered amiodarone were susceptible to developing myxedema coma. Utilizing the Cochrane guidelines, a comprehensive review of databases such as Medline (PubMed), Science Direct, CINAHL Cochrane, and Google Scholar was undertaken to examine case reports on amiodarone-induced myxedema coma. Following stringent criteria for inclusion, 12 pertinent case reports were identified. These findings suggested a high probability of myxedema coma development in patients who had been administered amiodarone. Specifically, patients who received an oral dosage of 100-200 mg of amiodarone were reported to have developed bradycardia and hypothermia alongside elevated thyroid-stimulating hormone (TSH) levels. Upon diagnosis, the majority of patients were treated with a regimen of levothyroxine and hydrocortisone medication. Despite the myriad potential causes of myxedema coma complicating the diagnosis, it was found that through a combination of clinical symptoms and serum TSH measurements, a confirmed diagnosis could be reached. Furthermore, it was observed that amiodarone-induced myxedema coma responded favorably to treatment with levothyroxine and glucocorticoids.

Real-life data on the impact of medical therapy for amiodarone-induced thyrotoxicosis on CV events and hospitalizations

CONTEXT

Patients with amiodarone-induced thyrotoxicosis (AIT) often receive the initial therapy for thyrotoxicosis in several different medical settings before admission to a referral center. Whether the first-line medical therapy (i.e. therapies for thyrotoxicosis at first diagnosis of AIT) affects the outcome of AIT patients is unknown.

STUDY DESIGN

Single-center historical-prospective cohort study of 313 AIT patients.

METHODS

Clinical and biochemical data were collected at first diagnosis, at a referral center, and during the course of AIT. Primary outcomes were cardiovascular events and hospitalizations. First-line therapies were considered appropriate when they included glucocorticoids for type 2 AIT and methimazole for type 1 AIT at the approved dosage, either alone (optimal medical therapy, OMT) or in combination (right-dose combination therapy, RCT). Other therapies were considered not appropriate, including no therapy. Duration of exposure to thyrotoxicosis was the time from first diagnosis of AIT to its remission.

RESULTS

34.5% patients received appropriate therapies (28.1% OMT, 6.4% RCT), whereas the remaining (65.5%) received non-appropriate therapies. Cardiovascular events, and hospitalizations were more frequent in patients who received non-appropriate therapies (33.2% vs 4.5%, and 24.9% vs 6.5%, respectively; p<0.0001 for both). Appropriate therapies reduced serum thyroid hormone concentrations (p=0.018) from first diagnosis to referral, unlike the non-appropriate therapies. The duration of exposure to thyrotoxicosis was longer in patients receiving non-appropriate therapies and was a risk factor for arrhythmias (HR 1.004, p=0.0008), MACEs (HR 1.004, p=0.020) and hospitalizations (HR 1.006, p<.0001).

CONCLUSIONS

The first medical therapy of AIT influences the exposure time to thyrotoxicosis and the occurrence of cardiovascular events and hospitalizations.

The Use of 99mTc-Methoxy-isobutyl-isonitrile (sestaMIBI) Uptake on Scintigraphy (99m-STS) in Amiodarone-Induced Thyrotoxicosis: Case Series and Review of the Literature

Amiodarone is a class III antiarrhythmic drug, used by cardiologists to treat arrhythmia including atrial fibrillation (A fib) and ventricular fibrillation. However, amiodarone is associated with endocrine dysfunction including both hypo- and hyperthyroidism. In the literature, two types of amiodarone-induced thyrotoxicosis (AIT) were described: AIT-1 and AIT-2. Mixed AIT also called AIT type 3 (AIT-3) has been described in the literature when the cases do not have a typical presentation. In order to differentiate different types of AIT, various clinical, biochemical, and radiological tools have been proposed. The use of ^99mTc-methoxy-isobutyl-isonitrile (sestaMIBI) uptake on scintigraphy (^99m-STS) has been suggested in the literature in only few studies (no large retrospective or prospective studies have been established in the United States). We present a case series describing 5 patients presenting to the University of Arizona with AIT where we used ^99m-STS to assess in diagnosis and treatment of different types of AIT followed by a review of the literature.

Amiodarone-Induced Thyrotoxicosis: Differential Diagnosis Using 99mTc-SestaMIBI and Target-to-Background Ratio (TBR)

PURPOSE OF THE REPORT

Distinguishing between amiodarone-induced thyrotoxicosis (AIT) caused by excessive hormone synthesis (AIT-1) or by a destructive process (AIT-2) has important therapeutic implications, but is still difficult and debated. Tc-sestaMIBI thyroid scintigraphy (99m-STS) has been proposed as a tool for classifying the two forms.

MATERIAL AND METHODS

30 AIT patients (11 females and 19 males) who underwent 99m-STS were retrospectively assessed for the present study. For each patient, a target-to-background ratio (TBR) was obtained on planar images. The TBR was then correlated with the qualitative assessment of the scans and the final clinical diagnosis.

RESULTS

Considering clinical response to treatment as the gold standard for differential diagnosis, 14 cases of AIT-1, 12 of AIT-2, and 4 mixed forms were identified. 99m-STS was able to qualitatively identify all the mixed forms, while 1/14 AIT-1 and 6/12 AIT-2 cases were misdiagnosed as mixed forms. When the quantitative index (the TBR) was compared with the final clinical diagnosis, ROC curve analysis enabled us to identify an IBR of 0.482 during 99m-STS as a cut-off capable of discriminating between AIT-1 and AIT-2, with 100% specificity and 91.7% sensitivity (P < 0.0001, area under the curve: 0.982).

CONCLUSIONS

Taking the TBR into consideration, 99m-STS proved a very useful tool for distinguishing AIT-1 from AIT-2, and thus offering patients appropriate treatment as of their diagnosis. This approach can avoid pointless and potentially dangerous combined overtreatments, and may speed up the return to normal thyroid function, which is crucial in AIT patients suffering from heart disease.

[Challenges in the management of amiodarone-induced thyrotoxicosis]

Amiodarone, a benzofuranic iodine-rich pan antiarrhythmic drug, is frequently associated with thyroid dysfunction. This side effect is heterogeneous and unpredicted, motivating regular evaluation of thyroid function tests. In contrary to hypothyroidism, amiodarone-induced thyrotoxicosis (AIT) is a challenging situation owing to the risk of deterioration of the general and cardiac status of such debilitating patients. Classically, AIT is either an iodine-induced thyrotoxicosis in patients with an abnormal thyroid (type I), or due to a subacute thyroiditis on a "healthy" thyroid (type II). Even if many studies tried to better identify the types of AIT, the diagnostic dilemma of type of AIT could be present, and many patients are treated by an association of antithyroid drugs (useful for type I AIT) with corticoids (useful for type II AIT). Being the main etiological factor in AIT, amiodarone is supposed to be stopped, but it could remain the only anti-arrhythmic option that is needed to be either continued or reintroduced to improve the cardiovascular survival. Recently, many studies demonstrated that amiodarone could be continued or reintroduced in patients with history of type II AIT. Nevertheless, in the other patients, amiodarone maintenance complicates the therapeutic response to the antithyroid drugs and increases the risk of AIT recurrence. Thus, amiodarone therapy is preferred to be interrupted. In such patients, thyroid ablation is recommended once AIT is under control.

Issues in amiodarone-induced thyrotoxicosis: Update and review of the literature

Amiodarone, a benzofuranic iodine-rich pan-anti-arrhythmic drug, induces amiodarone-induced thyrotoxicosis (AIT) in 7-15% of patients. AIT is a major issue due to its typical severity and resistance to anti-thyroid measures, and to its negative impact on cardiac status. Classically, AIT is either an iodine-induced thyrotoxicosis in patients with abnormal thyroid (type 1), or due to acute thyroiditis in a "healthy" thyroid (type 2). Determination of the type of AIT is a diagnostic dilemma, as characteristics of both types may be present in some patients. As it is the main etiological factor in AIT, it is recommended that amiodarone treatment should be stopped; however, it may be the only anti-arrhythmic option, needing to be either continued or re-introduced to improve cardiovascular survival. Recently, a few studies demonstrated that amiodarone could be continued or re-introduced in patients with history of type-2 AIT. However, in the other patients, it is recommended that amiodarone treatment be interrupted, to improve response to thioamides and to alleviate the risk of AIT recurrence. In such patients, thyroidectomy is recommended once AIT is under control, allowing safe re-introduction of amiodarone.

Thyroidectomy for Amiodarone-Induced Thyrotoxicosis: Mayo Clinic Experience

Context

Amiodarone-induced thyrotoxicosis (AIT) is a difficult diagnostic and management challenge, especially during severe thyrotoxicosis accompanied by cardiovascular compromise.

Objective

To evaluate thyroidectomy for the management of AIT.

Design

Retrospective cohort study of adults with noncongenital heart disease with AIT after >3 months of amiodarone who underwent thyroidectomy from 1 November 2002 to 31 December 2016.

Setting

Referral center.

Patients

The group was comprised of 17 patients.

Main Outcome Measures

Thyroid function, left ventricular ejection fraction (LVEF), and surgical complications were the main outcome measures.

Results

Patients had median age of 60 years, 82.4% were male, and 47% had systolic heart failure. At diagnosis, median TSH was 0.005 mIU/L, median free T4 was 3.25 ng/dL, and total T3 was 198.5 ng/dL. We classified five patients as type 1 and type 2 and two patients as mixed; five patients remained undefined. The most common surgical indications were medically refractory disease, worsening cardiac status, and severe thyrotoxicosis requiring prompt resolution. Within 1 week post-thyroidectomy, median TSH was 0.565 mIU/L, and free T4 was 1.8 ng/dL. Median LVEF improved by 8% in patients with systolic heart failure. Seven patients had a complication within 30 days postsurgery (rehospitalization, n = 4; cervical hematoma, n = 2; recurrent arrhythmia, n = 2; symptomatic hypocalcemia, n = 1; death, n = 1). A larger thyroid gland was a risk factor for complications.

Conclusions

Thyroidectomy resulted in rapid resolution of thyrotoxicosis. Its complication rate was higher than for non-AIT indications but lower than previously reported in a similar population of high-risk surgical patients.

Global epidemiology of hyperthyroidism and hypothyroidism

Thyroid hormones are essential for growth, neuronal development, reproduction and regulation of energy metabolism. Hypothyroidism and hyperthyroidism are common conditions with potentially devastating health consequences that affect all populations worldwide. Iodine nutrition is a key determinant of thyroid disease risk; however, other factors, such as ageing, smoking status, genetic susceptibility, ethnicity, endocrine disruptors and the advent of novel therapeutics, including immune checkpoint inhibitors, also influence thyroid disease epidemiology. In the developed world, the prevalence of undiagnosed thyroid disease is likely falling owing to widespread thyroid function testing and relatively low thresholds for treatment initiation. However, continued vigilance against iodine deficiency remains essential in developed countries, particularly in Europe. In this report, we review the global incidence and prevalence of hyperthyroidism and hypothyroidism, highlighting geographical differences and the effect of environmental factors, such as iodine supplementation, on these data. We also highlight the pressing need for detailed epidemiological surveys of thyroid dysfunction and iodine status in developing countries.

A survey of current approaches to thyroid nodules and thyroid operations

INTRODUCTION

Thyroid nodules are commonly seen. Our aim is to learn the behaviors and operational attitudes of surgeons approaching the thyroid nodules. In a literature search, our study is the first and only study performed merely on surgeons.

MATERIALS- METODS

This cross-sectional study was done between June 2014-January 2015. The questionnaire consists of 25 questions. Initially, general questions consisting of demographic findings were asked. In step 2, questions consisting of the index case and case variants were asked. Results were compared with American Thyroid Association, European Thyroid Association guidelines, and Australia survey results. In the last step, questions about thyroid operations were asked.

RESULTS

A total of 301 surgeons responded to the survey. The response rate was approximately 20%. Thirty nine were female and 262 were male. For the question that asks the diameter of the thyroid nodule that will require a thyroid fine needle aspiration biopsy (TFNAB), 47.5% of the surgeons will require a TFNAB for 1-2 cm solid nodules. 40.15% of the surgeons required a TFNAB regardless of size. 46.1% of the surgeons who required a TFNAB between 1 and 2 cm solid nodules also required scintigraphy at diagnosis of suppressed TSH case variant.

CONCLUSION

In this survey, we identified differences from up-to-date guidelines about approaching thyroid nodules and perioperative thyroid surgery. From our perspective, surgeons need updated training requirements. This can be done with updated seminars across the country. Thereby approaches may become standard and consequently patients may have qualified services.

Diagnosis and Management of Noncardiac Complications in Adults With Congenital Heart Disease: A Scientific Statement From the American Heart Association

Life expectancy and quality of life for those born with congenital heart disease (CHD) have greatly improved over the past 3 decades. While representing a great advance for these patients, who have been able to move from childhood to successful adult lives in increasing numbers, this development has resulted in an epidemiological shift and a generation of patients who are at risk of developing chronic multisystem disease in adulthood. Noncardiac complications significantly contribute to the morbidity and mortality of adults with CHD. Reduced survival has been documented in patients with CHD with renal dysfunction, restrictive lung disease, anemia, and cirrhosis. Furthermore, as this population ages, atherosclerotic cardiovascular disease and its risk factors are becoming increasingly prevalent. Disorders of psychosocial and cognitive development are key factors affecting the quality of life of these individuals. It is incumbent on physicians who care for patients with CHD to be mindful of the effects that disease of organs other than the heart may have on the well-being of adults with CHD. Further research is needed to understand how these noncardiac complications may affect the long-term outcome in these patients and what modifiable factors can be targeted for preventive intervention.

2016 American Thyroid Association Guidelines for Diagnosis and Management of Hyperthyroidism and Other Causes of Thyrotoxicosis

BACKGROUND

Thyrotoxicosis has multiple etiologies, manifestations, and potential therapies. Appropriate treatment requires an accurate diagnosis and is influenced by coexisting medical conditions and patient preference. This document describes evidence-based clinical guidelines for the management of thyrotoxicosis that would be useful to generalist and subspecialty physicians and others providing care for patients with this condition.

METHODS

The American Thyroid Association (ATA) previously cosponsored guidelines for the management of thyrotoxicosis that were published in 2011. Considerable new literature has been published since then, and the ATA felt updated evidence-based guidelines were needed. The association assembled a task force of expert clinicians who authored this report. They examined relevant literature using a systematic PubMed search supplemented with additional published materials. An evidence-based medicine approach that incorporated the knowledge and experience of the panel was used to update the 2011 text and recommendations. The strength of the recommendations and the quality of evidence supporting them were rated according to the approach recommended by the Grading of Recommendations, Assessment, Development, and Evaluation Group.

RESULTS

Clinical topics addressed include the initial evaluation and management of thyrotoxicosis; management of Graves' hyperthyroidism using radioactive iodine, antithyroid drugs, or surgery; management of toxic multinodular goiter or toxic adenoma using radioactive iodine or surgery; Graves' disease in children, adolescents, or pregnant patients; subclinical hyperthyroidism; hyperthyroidism in patients with Graves' orbitopathy; and management of other miscellaneous causes of thyrotoxicosis. New paradigms since publication of the 2011 guidelines are presented for the evaluation of the etiology of thyrotoxicosis, the management of Graves' hyperthyroidism with antithyroid drugs, the management of pregnant hyperthyroid patients, and the preparation of patients for thyroid surgery. The sections on less common causes of thyrotoxicosis have been expanded.

CONCLUSIONS

One hundred twenty-four evidence-based recommendations were developed to aid in the care of patients with thyrotoxicosis and to share what the task force believes is current, rational, and optimal medical practice.

The presence of anti-thyroglobulin (TgAb) and/or anti-thyroperoxidase antibodies (TPOAb) does not exclude the diagnosis of type 2 amiodarone-induced thyrotoxicosis

PURPOSE

It is widely accepted that type 2 amiodarone-induced thyrotoxicosis (AIT) generally occurs in patients with a normal thyroid gland without signs of thyroid autoimmunity. However, it is currently unknown if the presence of anti-thyroglobulin (TgAb) and/or anti-thyroperoxidase antibodies (TPOAb) in AIT patients without other signs of an underlying thyroid disease may impair the response to glucocorticoid therapy.

METHODS

We performed a pilot retrospective cohort study with matched-subject design and an equivalence hypothesis, comparing the response to glucocorticoid therapy between 20 AIT patients with a normal thyroid gland, low radioiodine uptake, undetectable TSH receptor antibodies and positive TgAb and/or TPOAb (Ab+ group), and 40 patients with the same features and absent thyroid antibodies (Ab- group).

RESULTS

The mean cure time was 54 ± 68 days in the Ab+ group and 55 ± 49 days in the Ab- group (p = 0.63). The equivalence test revealed an equivalent cure rate after 60, 90 and 180 days (p = 0.67, 0.88 and 0.278, respectively). The occurrence of permanent hypothyroidism was higher in the Ab+ group than in the Ab- group (26.3 vs 5.13 %, p = 0.032).

CONCLUSIONS

The presence of TgAb and/or TPOAb does not affect the response to glucocorticoid therapy, suggesting that the patients with features of destructive form of AIT should be considered as having a type 2 AIT irrespective of the presence of TGAb or TPOAb. These patients have a higher risk of developing hypothyroidism after the resolution of thyrotoxicosis and should be monitored accordingly.

Practical Management Guide for Clinicians Who Treat Patients with Amiodarone

Amiodarone, an iodinated benzofuran derivative with Class I, II, III, and IV antiarrhythmic properties, is the most commonly used antiarrhythmic drug used to treat supraventricular and ventricular arrhythmias. Appropriate use of this drug, with its severe and potentially life-threatening adverse effects, requires an essential understanding of its risk-benefit properties in order to ensure safety. The objective of this review is to afford clinicians who treat patients receiving amiodarone an appropriate management strategy for its safe use. The authors of this consensus management guide have thoroughly reviewed and evaluated the existing literature on amiodarone and apply this information, along with the collective experience of the authors, in its development. Provided are management guides on the intravenous and oral dosing of amiodarone, appropriate outpatient follow-up of patients taking the drug, its recognized adverse effects, and recommendations on when to consult specialists to help in patient management. All clinicians must be cognizant of the appropriate use, follow-up, and adverse reactions of amiodarone. The responsibility incurred by those treating such patients cannot be overemphasized.

Dysfunction of the thyroid gland during amiodarone therapy: a study of 297 cases

AIM

This study aims to explore and compare the efficacy of radioiodine treatment (RIT) in hyperthyroid and euthyroid patients who have been treated with amiodarone (AM) in the past or are currently undergoing AM treatment. Clinical observation of a group of patients with amiodarone-induced hypothyroidism during a 12-month follow-up period was used for comparison.

DESIGN

This was a observational, two-centered study. Patients were assessed at baseline and at 2 months, 6 months, 8 months, and 12 months after RIT.

PATIENTS

Group A: At baseline (61 males [M] and 17 females [F], mean age 50±19 years), there were 78 euthyroid patients with cardiac arrhythmias, who were treated with AM and developed amiodarone-induced thyrotoxicosis, and currently require retreatment with AM. Group B: Hyperthyroid patients (92 M and 26 F, mean age 72±11.8 years) after AM therapy in the past. Group C: Hyperthyroid patients (66 M and 13 F, mean age 63.9±13.2 years) currently treated by AM. Group D: Hypothyroid patients (6 M and 16 F, mean age 61.4±10.4 years) after AM therapy. The patients from Groups A, B, and C were retreated with AM after ~3-6 weeks of RIT.

RESULTS

In Group A, after 12 months of RIT therapy, recurrent thyrotoxicosis was observed in six (7.7%) cases, and persistent hypothyroidism was diagnosed in 42 (53.8%) cases. In Group B, hyperthyroidism occurring during treatment with AM was found in 40 (33.9%) patients, and permanent hypothyroidism was observed in eleven (12.5%) cases. After annual follow-up in Group C, nine (11.4%) patients were diagnosed with hypothyroidism, while 27 (34.1%) patients were diagnosed with hyperthyroidism. In Group D, all patients had permanent hypothyroidism and when the concentration of serum thyroid-stimulating hormone was >10 µIU/mL, l-thyroxine was applied.

CONCLUSION

Our study showed that radioiodine administration is advisable in certain circumstances, even in euthyroid patients. It allows for continuation of further long-term AM treatment. Additionally, RIT allows for the reintroduction of AM therapy that was previously terminated. Hence, it can help control life-threatening tachyarrhythmias and decrease episodes of thyrotoxicosis.

Amiodarone-Induced Thyrotoxicosis Recurrence After Amiodarone Reintroduction

Reintroduction of amiodarone in patients with a history of amiodarone-induced thyrotoxicosis (AIT) is rarely used. To date, the risk of AIT recurrence after amiodarone reintroduction is unpredicted. The aim of the study was to evaluate the risk of AIT recurrence. Retrospectively, from 2000 to 2011, all euthyroid patients with a history of AIT with amiodarone reintroduction were included. Type and severity of the first AIT, amiodarone chronology, and thyroid function evolution after reintroduction of amiodarone were investigated: 46 of 172 patients with AIT history needed amiodarone reintroduction. At first AIT episode, the mean age was 62.2 ± 16 years with male gender predominance; 65% of patients were classified as type 1 AIT. AIT recurred in 14 patients (30%), 12 patients developed hypothyroidism (26%), and 20 patients remained euthyroid (44%). Characteristics of type 1 AIT during the first episode, namely briefer exposure period to amiodarone and longer duration of treatment to normalize thyroid hormones, were predictive of AIT recurrence; 73% of patients (8 of 11) with previous episode of type 1 AIT, who did not receive a preventive thioamide treatment, developed a second episode of AIT. Thioamide preventive treatment could be useful to prevent type 1 AIT recurrence. In conclusion, AIT recurrence after amiodarone reintroduction is 4 times more frequent in patients with type 1 AIT history. Thyroid ablation before amiodarone reintroduction in patients with a history of type 1 AIT is preferred. Preventive thioamide treatment could be suggested in patients with type 1 AIT history pending for surgery.

Thyrotoxicosis associated with the use of amiodarone: the utility of ultrasound in patient management

Amiodarone is an anti-arrhythmic drug that commonly affects the thyroid, causing hypothyroidism or thyrotoxicosis. Amiodarone-induced thyrotoxicosis (AIT) is caused by excessive thyroid hormone biosynthesis in response to iodine load in autonomously functioning thyroid glands with pre-existing nodular goitre or underlying Graves' disease (type 1 or AIT 1), or by a destructive thyroiditis typically occurring in normal glands (type 2 or AIT 2). Indeterminate or mixed forms are also recognized. The distinction is clinically useful as AIT 1 is treated predominantly with thionamides, whereas AIT 2 is managed with glucocorticoids. We review the tools used to differentiate type 1 from type 2 thyrotoxicosis, with specific reference to the imaging modalities used.

Amiodarone-related thyroid dysfunction

Nowadays, amiodarone is the most commonly used antidysrhythmic drug in clinical practice. It is highly effective in the management of recurrent ventricular dysrhythmias, paroxysmal supraventricular dysrhythmias, including atrial fibrillation and flutter, and in the maintenance of sinus rhythm after electrical cardioversion of atrial fibrillation. Moreover, it has the added benefit of being well tolerated in patients with both normal and impaired left ventricular systolic function. Despite amiodarone's potent antidysrhythmic actions, its use is hampered by numerous adverse effects on various organs, including the thyroid. Adverse effects are becoming more prevalent given the increasing incidence of dysrhythmias and wider amiodarone use. Thus, physicians and patients should both be aware of the potential thyroid-specific sequelae. However, amiodarone is likely to remain a significant problem for endocrinologists as concerns exist over the use of the new alternative antiarrhythmic agent, dronedarone, especially in patients with heart failure and left ventricular dysfunction because of the risk of hepatic injury and increased mortality. The final diagnostic and therapeutic approaches must be discussed among the patient, the general practitioner, the cardiologist, and the endocrinologist.

Amiodarone-induced thyrotoxic thyroiditis: a diagnostic and therapeutic challenge

Amiodarone is an iodine-based, potent antiarrhythmic drug bearing a structural resemblance to thyroxine (T4). It is known to produce thyroid abnormalities ranging from abnormal thyroid function testing to overt hypothyroidism or hyperthyroidism. These adverse effects may occur in patients with or without preexisting thyroid disease. Amiodarone-induced thyrotoxicosis (AIT) is a clinically recognized condition commonly due to iodine-induced excessive synthesis of thyroid, also known as type 1 AIT. In rare instances, AIT is caused by amiodarone-induced inflammation of thyroid tissue, resulting in release of preformed thyroid hormones and a hyperthyroid state, known as type 2 AIT. Distinguishing between the two states is important, as both conditions have different treatment implications; however, a mixed presentation is not uncommon, posing diagnostic and treatment challenges. We describe a case of a patient with amiodarone-induced type 2 hyperthyroidism and review the current literature on the best practices for diagnostic and treatment approaches.

Cost effectiveness of a pharmacist-led information technology intervention for reducing rates of clinically important errors in medicines management in general practices (PINCER)

BACKGROUND AND OBJECTIVE

We recently showed that a pharmacist-led information technology-based intervention (PINCER) was significantly more effective in reducing medication errors in general practices than providing simple feedback on errors, with cost per error avoided at £79 (US$131). We aimed to estimate cost effectiveness of the PINCER intervention by combining effectiveness in error reduction and intervention costs with the effect of the individual errors on patient outcomes and healthcare costs, to estimate the effect on costs and QALYs.

METHODS

We developed Markov models for each of six medication errors targeted by PINCER. Clinical event probability, treatment pathway, resource use and costs were extracted from literature and costing tariffs. A composite probabilistic model combined patient-level error models with practice-level error rates and intervention costs from the trial. Cost per extra QALY and cost-effectiveness acceptability curves were generated from the perspective of NHS England, with a 5-year time horizon.

RESULTS

The PINCER intervention generated £2,679 less cost and 0.81 more QALYs per practice [incremental cost-effectiveness ratio (ICER): -£3,037 per QALY] in the deterministic analysis. In the probabilistic analysis, PINCER generated 0.001 extra QALYs per practice compared with simple feedback, at £4.20 less per practice. Despite this extremely small set of differences in costs and outcomes, PINCER dominated simple feedback with a mean ICER of -£3,936 (standard error £2,970). At a ceiling 'willingness-to-pay' of £20,000/QALY, PINCER reaches 59 % probability of being cost effective.

CONCLUSIONS

PINCER produced marginal health gain at slightly reduced overall cost. Results are uncertain due to the poor quality of data to inform the effect of avoiding errors.

Amiodarone-induced thyroid dysfunction in Taiwan: a retrospective cohort study

BACKGROUND

The incidence and risk factors of amiodarone-induced thyroid dysfunction are variable in the literature.

OBJECTIVE

The aim of this study was to investigate the clinical and biochemical features and risk factors of amiodarone-induced thyroid dysfunction in Taiwan.

SETTING

This study was conducted at a tertiary referral center for arrhythmia.

METHOD

Retrospective analysis of patients treated with amiodarone during the years 2008-2009 was performed.

MAIN OUTCOME MEASURE

Incidence and risk factors of amiodarone-induced thyrotoxicosis (AIT) and amiodarone-induced hypothyroidism (AIH) were assessed.

RESULTS

Of the 527 patients, 437 (82.9 %) remained euthyroid, 21 (4.0 %) developed AIT, and 69 (13.1 %) were affected with AIH. In univariate analysis, AIT was associated with younger age, and the risk factors for AIH included older age, higher baseline thyroid stimulating hormone (TSH) titer, lower baseline free T4 level, lower cumulative amiodarone dosage, and shorter amiodarone treatment duration. Cox regression analysis was performed to determine the different risk categories in the elderly population of age 65-74 (young-old), 75-84 (old-old), and ≥85 years old (oldest-old). Additionally increased risk of AIH was found in the groups of old-old (HR 2.09, 95 % CI 1.11-3.96) and oldest-old (HR 2.57, 95 % CI 1.21-4.75). In the multivariate analysis of risk factors for AIH, baseline TSH level (HR 1.38, 95 % CI 1.12-1.70) and cumulative amiodarone dosage (HR 0.95, 95 % CI 0.93-0.97) remained statistically significant.

CONCLUSION

AIH was much more common than AIT in Taiwan, an area with sufficient iodine intake. Higher baseline TSH level was the predominant independent risk factor for the development of AIH.

Amiodarone-induced thyroid dysfunction

Amiodarone is an effective medication for the treatment of cardiac arrhythmias. Originally developed for the treatment of angina, it is now the most frequently prescribed antiarrhythmia drug despite the fact that its use is limited because of potential serious side effects including adverse effects on the thyroid gland and thyroid hormones. Although the mechanisms of action of amiodarone on the thyroid gland and thyroid hormone metabolism are poorly understood, the structural similarity of amiodarone to thyroid hormones, including the presence of iodine moieties on the inner benzene ring, may play a role in causing thyroid dysfunction. Amiodarone-induced thyroid dysfunction includes amiodarone-induced thyrotoxicosis (AIT) and amiodarone-induced hypothyroidism (AIH). The AIT develops more commonly in iodine-deficient areas and AIH in iodine-sufficient areas. The AIT type 1 usually occurs in patients with known or previously undiagnosed thyroid dysfunction or goiter. The AIT type 2 usually occurs in normal thyroid glands and results in destruction of thyroid tissue caused by thyroiditis. This is the result of an intrinsic drug effect from the amiodarone itself. Mixed types are not uncommon. Patients with cardiac disease receiving amiodarone treatment should be monitored for signs of thyroid dysfunction, which often manifest as a reappearance of the underlying cardiac disease state. When monitoring patients, initial tests should include the full battery of thyroid function tests, thyroid-stimulating hormone, thyroxine, triiodothyronine, and antithyroid antibodies. Mixed types of AIT can be challenging both to diagnose and treat and therapy differs depending on the type of AIT. Treatment can include thionamides and/or glucocorticoids. The AIH responds favorably to thyroid hormone replacement therapy. Amiodarone is lipophilic and has a long half-life in the body. Therefore, stopping the amiodarone therapy usually has little short-term benefit.

Body mass index and the development of amiodarone-induced thyrotoxicosis in adults with congenital heart disease--a cohort study

INTRODUCTION

Amiodarone-induced thyrotoxicosis (AIT) is a recognized complication of amiodarone treatment with limited management options. Its predisposing factors are incompletely defined yet a higher prevalence was reported in adults with congenital heart disease (CHD). Therefore we sought to determine the incidence and risk factors for AIT in adults with CHD.

METHODS

At a tertiary care center we followed a historical cohort of amiodarone-treated CHD patients for the period 1987-2009. Follow-up concluded at AIT diagnosis or with last thyroid assessment on amiodarone. Cumulative incidence of AIT was calculated. AIT association with nutritional status was hypothesized a priori.

RESULTS

AIT developed in 23/169 patients or 13.6%. The AIT incidence peaked in the 3rd year at 7.7%. AIT patients had a lower body mass index (BMI) at AMIO initiation compared with the rest of the cohort (mean ± standard deviation: 21.9 ± 2.9 vs. 25.1 ± 5.0; p<0.001). Patients with BMI<21 were more likely to develop thyrotoxicosis (RR=6.1) compared to those with BMI>25 (p<0.001). Presence of goiter was strongly associated with AIT (RR 3.6, p=0.002). Affected patients had a trend for higher cyanotic heart disease prevalence (34.8% vs. 17.8%, p=0.059). On multivariate analysis body mass index and goiter remained independent predictors of outcome.

CONCLUSIONS

BMI<21 at initiation of amiodarone therapy and presence of goiter are strong predictors of AIT in this population. Its incidence is time dependent. These predictors can be used clinically in assessing overall impact of amiodarone therapy in congenital heart disease patients.

Amiodarone and the thyroid: a 2012 update

Amiodarone-induced thyroid dysfunction occurs in 15-20% of amiodarone-treated patients. Amiodarone-induced hypothyroidism (AIH) does not pose relevant problems, is easily controlled by L-thyroxine replacement, and does not require amiodarone withdrawal. Most frequently AIH develops in patients with chronic autoimmune thyroiditis. Amiodarone- induced thyrotoxicosis (AIT) is most frequently due to destructive thyroiditis (type 2 AIT) causing discharge of thyroid hormones from the damaged, but otherwise substantially normal gland. Less frequently AIT is a form of hyperthyroidism (type 1 AIT) caused by the iodine load in a diseased gland (nodular goiter, Graves' disease). A clearcut differentiation between the two main forms is not always possible, despite recent diagnostic advances. As a matter of fact, mixed or indefinite forms do exist, contributed to by both thyroid damage and increased thyroid hormone synthesis. Treatment of type 1 (and mixed forms) AIT is based on the use of thionamides, a short course of potassium perchlorate and, if treatment is not rapidly effective, oral glucocorticoids. Glucocorticoids are the first-line treatment for type 2 AIT. Amiodarone should be discontinued, if feasible from a cardiac standpoint. Continuation of amiodarone has recently been associated with a delayed restoration of euthyroidism and a higher chance of recurrence after glucocorticoid withdrawal. Whether amiodarone treatment can be safely reinstituted after restoration of euthyroidism is still unknown. In rare cases of AIT resistance to standard treatments, or when a rapid restoration of euthyroidism is advisable, total thyroidectomy represents a valid alternative. Radioiodine treatment is usually not feasible due to the low thyroidal iodine uptake.

Determinants and outcome of amiodarone-associated thyroid dysfunction

OBJECTIVE

Amiodarone is frequently associated with thyroid dysfunction. Identifying predictors for amiodarone-associated thyroid dysfunction and assessing treatment outcome may aid clinicians in daily practice.

METHODS

We included 303 consecutive patients with amiodarone therapy for cardiac arrhythmias (260 with atrial fibrillation and 43 with ventricular arrhythmias). Thyroid function tests were performed every 6 months.

RESULTS

Mean age was 63 ± 12 years and 66% was male. After median follow-up of 3·3 (0·1-24) years, 23 (8%) patients developed amiodarone-associated thyrotoxicosis (incidence rate 1·9 per 100 person years) and 18 (6%) hypothyroidism (incidence rate 1·1 per 100 person years). The only predictor for amiodarone-associated thyrotoxicosis was age <62 years [HR = 2·4 (95% CI 1·0-5·7), P = 0·05]. Predictors for amiodarone-associated hypothyroidism were thyroid stimulating hormone >1·4 mU/l at baseline [HR = 5·1 (95% CI 1·1-22·4), P = 0·03], left ventricular ejection fraction <45% [HR = 3·8 (95% CI 1·1-13·3), P = 0·04] and diabetes mellitus at baseline [HR = 3·3 (95% CI 1·1-10·3), P = 0·04]. Gender was not a predictor for amiodarone-associated thyroid dysfunction. Five out of 12 (42%) patients with thyrotoxicosis exhibited spontaneous normalization of thyroid function on continuation of amiodarone therapy. Mean time to normalization in the total group was 6·2 ± 3·3 months, with no difference between continuing or discontinuing amiodarone (6·6 ± 3·8 vs 5·8 ± 2·8 months, P = 0·5).

CONCLUSIONS

During median follow-up of 3·3 years, the incidence of amiodarone-associated thyrotoxicosis was higher compared to hypothyroidism. Only general predictors for amiodarone-associated thyroid dysfunction were observed. Discontinuation of amiodarone did not influence treatment outcome.

Environmental factors and thyroid autoimmunity

Thyroid autoimmune disease, a multifactorial organ-specific autoimmune disorder, is marking a constant increase worldwide. It is thought to be caused by multiple environmental factors triggering autoimmune response in genetically susceptible individuals, though the exact mechanisms linking environmental factors to thyroid autoimmunity are not as yet well understood. Nevertheless, there is increasing evidence that mainly nutritive factors and environmental pollution by metals and chemicals (e.g. organochlorines, pesticides) are the main factors in the present-day spread of this disease. This review presents an overview of the current knowledge regarding environmental factors, their association with genetics and their impact on the immune system.

Approach to the patient with amiodarone-induced thyrotoxicosis

Amiodarone, a benzofuranic iodine-rich antiarrhythmic drug, causes thyroid dysfunction in 15-20% of cases. Although amiodarone-induced hypothyroidism poses no particular problem, amiodarone-induced thyrotoxicosis (AIT) is a diagnostic and therapeutic challenge. There are two main forms of AIT: type 1, a form of iodine-induced hyperthyroidism, and type 2, a drug-induced destructive thyroiditis. However, mixed/indefinite forms exist that may be caused by both pathogenic mechanisms. Type 1 AIT usually occurs in abnormal thyroid glands, whereas type 2 AIT develops in apparently normal thyroid glands (or small goiters). Diagnosis of thyrotoxicosis is easy, based on the finding of increased free thyroid hormone concentrations and suppressed TSH levels. Thyroid radioactive iodine (RAI) uptake values are usually very low/suppressed in type 2 AIT, most commonly low or low-normal, but sometimes normal or increased in type 1 AIT despite the iodine load. Color flow Doppler sonography shows absent hypervascularity in type 2 and increased vascularity in type 1 AIT. Mixed/indefinite forms may have features of both AIT types. Thionamides represent the first-line treatment for type 1 AIT, but the iodine-replete gland is not very responsive; potassium perchlorate, by inhibiting thyroid iodine uptake, may increase the response to thionamides. Type 2 AIT is best treated by oral glucocorticoids. The response very much depends on the thyroid volume and the severity of thyrotoxicosis. Mixed/indefinite forms may require a combination of thionamides, potassium perchlorate, and steroids. RAI is usually not feasible in AIT due to low RAI uptake values. Thyroidectomy represents a valid option in cases resistant to medical therapy.

Effects of amiodarone therapy on thyroid function

Amiodarone is a benzofuran derivative approved for the treatment of cardiac arrhythmias. Traditionally classified as a class III antiarrhythmic agent, amiodarone possesses electrophysiologic properties of all four Vaughan-Williams classes. This drug, however, has high iodine content, and this feature plus the intrinsic effects on the body make amiodarone especially toxic to the thyroid gland. Treatment can result in a range of effects from mild derangements in thyroid function to overt hypothyroidism or thyrotoxicosis. The diagnosis and treatment of amiodarone-induced hypothyroidism is usually straightforward, whereas that of amiodarone-induced thyrotoxicosis and the ability to distinguish between the type 1 and type 2 forms of the disease are much more challenging. Dronedarone was approved in 2009 for the treatment of patients with atrial fibrillation. As amiodarone, dronedarone is a benzofuran derivative with similar electrophysiologic properties. In contrast to amiodarone, however, dronedarone is structurally devoid of iodine and has a notably shorter half-life. In studies reported before FDA approval, dronedarone proved to be associated with significantly fewer adverse effects than amiodarone, making it a more attractive choice for patients with atrial fibrillation or flutter, who are at risk of developing amiodarone-induced thyroid dysfunction.

Glucocorticoids are preferable to thionamides as first-line treatment for amiodarone-induced thyrotoxicosis due to destructive thyroiditis: a matched retrospective cohort study

CONTEXT

Type 2 amiodarone-induced thyrotoxicosis (AIT) is a destructive thyroiditis usually responsive to glucocorticoids; however, recent surveys showed that many expert thyroidologists worldwide use thionamides for type 2 AIT patients.

OBJECTIVE

The objective of the study was to compare the effectiveness of methimazole (MMI) or prednisone (GLU) in type 2 AIT patients who had a short cure time according to a published predictive model.

DESIGN

This was a matched retrospective cohort study.

SETTING

The study was conducted at a university center.

PATIENTS

Forty-two untreated type 2 AIT patients with a predicted cure time < or = 40 d were divided into two groups (MMI and GLU groups). After matching for the predicted cure time, patients in the GLU group were selected in a 1:1 ratio to patients in the MMI group.

INTERVENTION

Patients were treated with GLU or MMI for 40 d. Patients still thyrotoxic after 40 d continued glucocorticoids if in the GLU group or were switched to prednisone (MMI-GLU group) if in the MMI group.

MAIN OUTCOME MEASURE

Time and rate of cure (healing) at 40 d were measured.

RESULTS

Patients still thyrotoxic after 40 d were 23.8 +/- 9.3% in the GLU group and 85.7 +/- 7.6% in the MMI group (P = 0.000). The GLU and MMI-GLU groups did not significantly differ in the nonhealing rate at 40 d (P = 0.730). When patients in the MMI group were treated with glucocorticoids, 94.1% patients achieved euthyroidism within 40 d. However, the global median cure time (MMI period + prednisone period) was longer (60 d, 95% confidence interval 53.5-66.5 d) in the MMI-GLU group than the GLU group (21 d, 95% confidence interval 15.1-26.9 d).

CONCLUSIONS

Glucocorticoids are the first-line treatment in type 2 AIT, whereas thionamides play no role in this destructive thyroiditis.

Incidence and predictability of amiodarone-induced thyrotoxicosis and hypothyroidism

OBJECTIVES

To determine the incidence and predictability of amiodarone-induced thyrotoxicosis (AIT) and hypothyroidism (AIH) in patients with cardiomyopathy.

PATIENTS AND METHODS

A total of 72 patients (mean age 69 +/- 11 years) living in an area previously endemic for thyroid disease but with currently sufficient iodine intake were enrolled in this prospective study. All participants were treated with amiodarone for the first time. The course of thyroid function in patients with normal thyroid morphology and in those with goiter was monitored over a median follow-up period of eight months in 71 (98.6%) patients.

RESULTS

Of 72 participants, 18 (25.0%) had a morphologically normal thyroid gland as evidenced by sonography. The prevalence of thyroid dysfunction before initiation of amiodarone was 37.6% (27 of 72) with almost equal distribution between hypothyroidism and hyperthyroidism (14 and 13 patients). After treatment with amiodarone, thyroid dysfunction was diagnosed in 56.8% (25 of 44) of the patients without preexisting dysfunction. Of these 25 patients, nine (36%) developed either subclinical or overt AIH and 16 (64.0%) developed either subclinical or overt AIT. Although 61.1% (44 of 72) had normal thyroid function before initiation of amiodarone, this number decreased to 26.7% (19 of 71, P < 0.001) after treatment. Factors such as (99m)Tc-pertechnetate scan uptake, thyroid autoimmunity, age, thyroid autonomy or abnormal thyroid morphology were not significantly associated with the development of thyroid dysfunction.

CONCLUSIONS

Prevalence of thyroid dysfunction was high in elderly patients treated with amiodarone. Cases of AIT and AIH occurred in patients with and without preexisting thyroid disorders. Because of the high incidence of amiodarone-induced thyroid dysfunction, regular testing of thyroid function is mandatory during and following amiodarone treatment.

Benzofuran derivatives and the thyroid

Amiodarone and dronedarone are two clinically important benzofuran derivatives. Amiodarone has been used widely for treating resistant tachyarrhythmias in the past three decades. However amiodarone and its main metabolically active metabolite desethylamiodarone can adversely affect many organs, including the thyroid gland. Amiodarone-induced thyroid disorders are common and often present as a management challenge for endocrinologists. The pathogenesis of amiodarone-induced thyroid dysfunction is complex but the inherent effects of the drug itself as well as its high iodine content appear to play a central role. The non-iodinated dronedarone also exhibits anti-arrhythmic properties but appears to be less toxic to the thyroid. This review describes the biochemistry of benzofuran derivatives, including their pharmacology and the physiology necessary for understanding the cellular mechanisms involved in their actions. The known effects of these compounds on thyroid action are described. Recommendations for management of amiodarone-induced hypothyroidism and thyrotoxicosis are suggested. Dronedarone appears to be an alternative but less-effective anti-arrhythmic agent and it does not have adverse effects on thyroid function. It may have a future role as an alternative agent in patients being considered for amiodarone therapy especially those at high risk of developing thyroid dysfunction but not in severe heart failure.

Diagnosis and management of amiodarone-induced thyrotoxicosis: similarities and differences between North American and European thyroidologists

OBJECTIVE

To investigate how North American thyroidologists assess and treat amiodarone-induced thyrotoxicosis (AIT) and to compare the results with those of the same questionnaire-based survey previously carried out among European thyroidologists.

DESIGN

Members of the American Thyroid Association (ATA) with clinical interests were sent by e-mail a questionnaire on the diagnosis and management of AIT, 115 responses were received from the United States and Canada, representing about one-third of ATA members with clinical interests.

RESULTS

The majority of respondents (91%vs. 68% in Europe, P < 0.05) see < 10 new cases of AIT per year, and AIT seems less frequent than amiodarone-induced hypothyroidism (AIH) in North America (34% and 66% of amiodarone-induced thyroid dysfunction, respectively, vs. 75% and 25%, respectively, in Europe, P < 0.001). When AIT is suspected, in North America hormonal assessment is mostly based on serum free T4 (FT4) and TSH measurements, while serum free T3 (FT3) determination is requested less frequently than in Europe; thyroid autoimmunity is included in the initial assessment less than in Europe. Most commonly used additional diagnostic procedures include, as in Europe, thyroid colour-flow Doppler sonography, and to a lesser extent, thyroid radioactive iodine uptake and scan, but Europeans tend to request multiple tests more than North Americans. Withdrawal of amiodarone is more often considered unnecessary by North American thyroidologists (21%vs. 10% in Europe in type 1 AIT, P < 0.05, 34%vs. 20% in type 2 AIT, P < 0.05). In type 1 AIT thionamides represent the treatment of choice for North Americans as well as for Europeans, but the former use them as monotherapy in 65%vs. 51% of Europeans (P < 0.05) who more often consider potassium perchlorate as an useful addition (31%vs. 15% of North Americans, P < 0.01). Glucocorticoids are the selected treatment for type 2 AIT, alone (62%vs. 46% in Europe, P < 0.05) or in association with thionamides (16%vs. 25% in Europe, P = NS). After restoration of euthyroidism, thyroid ablation in the absence of recurrent thyrotoxicosis is recommended in type 1 AIT less frequently by North Americans. If amiodarone therapy needs to be reinstituted, prophylactic thyroid ablation is advised by 76% in type 1 AIT, while a 'wait-and-see' strategy is adopted by 61% in type 2 AIT, similar to behaviour of European thyroidologists.

CONCLUSION

Similarities and differences exist between expert North American and European thyroidologists concerning the diagnosis and management of AIT. While differences reflect the frequent uncertainty of the underlying mechanism leading to AIT, similarities may represent the basis to refine the diagnostic criteria and to improve the therapeutic outcomes of this challenging clinical situation.

[Thyroid and treatment with amiodarone diagnosis, therapy and clinical management]

Amiodarone is a frequently used antiarrhythmic drug with a high antiarrhythmic potency. However, beside its antiarrhythmic effects Amiodarone also reveals a variety of adverse effects and drug-related complications. The affected organs include the eyes, skin, lungs, nervous system, liver, gastrointestinal tract and the thyroid. The thyroid is one of the most frequently affected organs by Amiodarone. An altered hormone equilibrium always occurs and has to be distinguished from Amiodarone induced hyperthyroidism and hypothyroidism. The differentiation of these states frequently causes problems and may even be a diagnostic and therapeutic challenge in certain cases. The article gives an overview on the interactions between Amiodarone and the thyroid, the diagnostic and therapeutic options and management strategies of patient on Amiodarone therapy in the view of thyroid function.

Treatment of amiodarone-associated thyrotoxicosis

BACKGROUND

A 75-year-old man had a myocardial infarction complicated by poor left ventricular function and non-sustained ventricular tachycardia. He began treatment with amiodarone and 12 months later developed symptoms of thyrotoxicosis.

INVESTIGATIONS

Thyroid function tests after commencement of amiodarone revealed a high-normal level of free T4 and low-normal level of free T3 with a normal serum TSH. When symptoms of thyrotoxicosis developed, significant rises in T4 and T3 levels and suppression of TSH were observed. Thyroid autoantibodies were detected and thyroid ultrasonography revealed a small multinodular goiter.

DIAGNOSIS

Amiodarone-induced thyrotoxicosis (AIT) with features consistent with both AIT type I (in which thyroid antibodies and nodular goiter are present) and AIT type II (which is not responsive to thionamide therapy and eventually leads to permanent hypothyroidism).

MANAGEMENT

The patient continued to be treated with amiodarone. He commenced thionamide (carbimazole) therapy but failed to improve, even after a dose increase. Glucocorticoid (prednisolone) therapy was therefore added. Combination therapy was associated with gradual clinical and biochemical improvement. The patient became persistently hypothyroid after stopping thionamide and glucocorticoid therapy and was stabilized on long-term thyroxine replacement.

Differential diagnosis and appropriate treatment of four thyrotoxic patients with Graves' disease required to take amiodarone due to life-threatening arrhythmia

We report the treatment of four thyrotoxic patients. Two were cases of type I amiodarone-induced thyrotoxicosis (AIT) treated with methimazole. The third Graves' disease patient, who became hypothyroid 25 years after subtotal thyroidectomy, developed type II AIT. Furthermore, one case with heart failure and ventricular tachycardia, who developed an adverse reaction to antithyroid agents and was prescribed amiodarone, underwent total thyroidectomy. The clinical course was uneventful, and the patient is doing well. Since amiodarone contains a large amount of iodine, it is frequently difficult to make a differential diagnosis. Surgical treatment of Graves' disease patients is recommended when immediate control of hyperthyroidism and heart failure is required.

A fatal case of recurrent amiodarone-induced thyrotoxicosis after percutaneous tracheotomy: a case report

Background

Amiodarone is a widely used antiarrythmic drug, which may produce secondary effects on the thyroid. In 14–18% of amiodarone-treated patients, there is overt thyroid dysfunction, usually in the form of amiodarone-induced thyrotoxicosis, which can be difficult to manage with standard medical treatment.

Case presentation

Presented is the case of a 65-year-old man, under chronic treatment of atrial fibrillation with amiodarone, who was admitted to the Intensive Care Unit with acute cardio-respiratory failure and fever. He was recently hospitalized with respiratory distress, attributed to amiodarone-induced pulmonary fibrosis. Clinical and laboratory investigation revealed thyrotoxicosis due to amiodarone treatment. He was begun on thionamide, prednisone and beta-blockers. After a short term improvement of his clinical status the patient underwent percutaneous tracheotomy due to weaning failure from mechanical ventilation, which led to the development of recurrent thyrotoxicosis, unresponsive to medical treatment. Finally, the patient developed multiple organ failure and died, seven days later.

Conclusion

We suggest that percutaneous tracheotomy could precipitate a thyrotoxic crisis, particularly in non-euthyroid patients suffering from concurrent severe illness and should be performed only in parallel with emergency thyroid surgery, when indicated.

Proportion of type 1 and type 2 amiodarone-induced thyrotoxicosis has changed over a 27-year period in Italy

CONTEXT

Two main forms of amiodarone-induced thyrotoxicosis (AIT) exist. Type 1 AIT is a form of iodine-induced hyperthyroidism. Its management is complex and includes thionamides, potassium perchlorate and, occasionally, thyroidectomy. Type 2 AIT is a destructive thyroiditis, responds to glucocorticoids, and usually does not require further thyroid treatment once euthyroidism has been restored.

OBJECTIVE

To assess retrospectively the prevalence and relative proportion of type 1 and type 2 AIT over a 27-year period at a tertiary referral centre in Italy.

PATIENTS

Consecutive AIT patients (n = 215) seen at the department of endocrinology of the University of Pisa between 1980 and 2006.

RESULTS

Type 1 AIT constituted the most frequent AIT form (60%) during the first years covered by this study. The annual mean number of type 1 AIT patients was 3.6 at the beginning of the study period, and 2.5 during the later years. In contrast, the mean annual number of new cases of type 2 AIT progressively increased from 2.4 to 12.5. Likewise, the proportion of type 2 AIT increased in a significant linear manner (P < 0.0001), currently accounting for 89% of AIT cases. Type 2 AIT patients showed a male preponderance, higher serum FT4/FT3 ratio (P < 0.002), lower 3-h and 24-h thyroidal radioactive iodine uptake values (P < 0.0001), and received a higher cumulative dose of amiodarone (P < 0.0001) than type 1 AIT patients.

CONCLUSIONS

Over a 27-year period, the epidemiology of AIT changed, as the prevalence of type 2 AIT progressively increased and that of type 1 remained constant. Thus, under most circumstances, endocrinologists nowadays deal with type 2 AIT, which is a destructive thyroiditis, generally treated successfully with glucocorticoids. Although no additional treatment is usually required after the destructive process subsides, periodic assessment of thyroid function is warranted, because of the occurrence of hypothyroidism (up to 17%) during long-term follow-up of these patients.

A practical guide for clinicians who treat patients with amiodarone: 2007

Amiodarone is commonly used to treat supraventricular and ventricular arrhythmias in various inpatient and outpatient settings. Over- and under-use of amiodarone is common, and data regarding patterns of use are sparse and largely anecdotal. Because of adverse drug reactions, proper use is essential to deriving optimal benefits from the drug with the least risk. This guide updates an earlier version published in 2000, reviews indications for use of amiodarone and recommends strategies to minimize adverse effects. The recommendations included herein are based on the best available data and the collective experience of the member of the writing committee.

Glucocorticoid response in amiodarone-induced thyrotoxicosis resulting from destructive thyroiditis is predicted by thyroid volume and serum free thyroid hormone concentrations

CONTEXT

Amiodarone-induced thyrotoxicosis (AIT) resulting from destructive thyroiditis (type 2) is commonly treated with glucocorticoids, but time needed to restore euthyroidism may be unacceptable for patients with underlying cardiac disorders.

OBJECTIVE

The objective of this prospective study was to identify factors affecting the response to glucocorticoids in a large cohort of patients with type 2 AIT followed prospectively.

SETTING

This study was conducted at university centers.

PATIENTS

Sixty-six untreated patients with type 2 AIT were enrolled in the study.

INTERVENTION

All patients were treated with prednisone (initial dose, 0.5 mg/kg.d) as long as needed to restore euthyroidism, defined as cure of AIT.

MAIN OUTCOME MEASURE

The main outcome measure was cure time.

RESULTS

The median cure time was 30 d (95% confidence interval, 23-37 d). Serum free T4 concentration (picograms per milliliter) and thyroid volume (milliliters per square meter) (and, to a lesser extent, serum free T3 concentration) at diagnosis were the main determinants of response to glucocorticoids, with a cure hazard ratio of 0.97 (95% confidence interval, 0.95-0.99; P = 0.005) and 0.84 (95% confidence interval, 0.77-0.91; P = 0.000) for unit of increment, respectively. AIT was cured in all patients with a complete follow-up; euthyroidism was reached in 30 d or less in 60% of patients but in more than 90 d in 16%. A prompt control of thyrotoxicosis (<or=30 d of treatment) was more frequent (77%) in patients with serum basal free T4 concentration no greater than 50 pg/ml and thyroid volume (normalized for body surface area) no greater than 12 ml/m2. The cure probability and the mean cure time in an individual patient can be obtained using a formula generated by multiple regression models.

CONCLUSIONS

Baseline serum thyroid hormone concentrations and thyroid volume help identify patients with type 2 AIT at risk of a delayed response to glucocorticoids.

Management of amiodarone-induced thyrotoxicosis in Latin America: an electronic survey

OBJECTIVE

To assess diagnostic and therapeutic approaches to amiodarone-induced thyrotoxicosis (AIT) among members of the Latin American Thyroid Society (LATS).

METHODS

LATS members responded to an online questionnaire that presented an index case (a 62-year-old man on amiodarone, with thyrotoxic symptoms and a nodular goitre) and a variant (same patient, no goitre).

RESULTS

About 25% of invited members responded to the questionnaire. Most respondents lived in iodine-sufficient areas and observed that amiodarone-induced hypothyroidism (AIH) is more common than AIT. Nearly all assessed TSH, and the most used combination of tests was TSH and free T4 (37%). Thyroid autoimmunity was assessed by about 90%. Interleukin-6 (IL-6) was useful to 80%. Additional tests ordered for the index case were: radioactive iodine uptake (RAIU; 57%), echo-colour Doppler sonography (ECDS; about 50%) and fine-needle aspiration biopsy (FNAB; 44%). For the variant, ECDS and RAIU were judged unhelpful by 16%. Most defined the index case as type I AIT and the variant as type II AIT, but 16% in LATS suggested a mixed form in the index case. As initial treatment, nearly all used thionamides in the index case [with potassium perchlorate (KClO(4)) in one-third], while glucocorticoids were indicated to the variant by 66%. Only about 5% considered amiodarone withdrawal unnecessary. If initial strategy is ineffective in type I AIT, KClO(4) (half) or glucocorticoids (a third) are added; in type II, glucocorticoids are indicated by most. Once euthyroidism is restored, ablative therapy is prescribed by a third of respondents for type I AIT.

CONCLUSIONS

There are several points of disagreement among thyroidologists regarding AIT management, mainly in the radiological evaluation and the approach to the already stabilized patient if amiodarone needs to be restarted.

Long-term outcome of thyroid function after amiodarone-induced thyrotoxicosis, as compared to subacute thyroiditis

BACKGROUND

Two main forms of amiodarone- induced thyrotoxicosis (AIT) exist: type 1 AIT is a condition of true hyperthyroidism developing in patients with pre-existing thyroid disorders, and usually requires thyroid ablative treatment. On the other hand, type 2 AIT is a form of destructive thyroiditis occurring in normal thyroids, the management of which usually consists in glucocorticoid treatment.

AIM

To assess the long-term outcome of thyroid function in a prospective study of type 2 AIT patients, as compared to patients with De Quervain's subacute thyroiditis (SAT).

PATIENTS AND METHODS

Sixty consecutive patients with type 2 AIT were evaluated during oral glucocorticoid treatment (oral prednisone 30 mg/day, gradually tapered and withdrawn over a 3-month period) and followed for 38+/-4 months (range 6-72) thereafter. Sixty consecutive patients with SAT, referred to our Institutes during the same period and treated with the same therapeutic schedule, served as controls.

RESULTS

Type 2 AIT patients were older (p<0.0001) and showed a larger male preponderance (M:F 3.6:1 vs 0.5:1, p<0.0001) than SAT patients. Mean serum free T4 (FT4) and free T3 (FT3) concentrations at diagnosis were increased in both conditions, but higher in type 2 AIT than in SAT (FT4 47.6+/-18.8 and 29.6+/-8.3 pmol/l, respectively, p<0.0001; FT3 15.4+/-7.0 and 11.2+/-3.0 pmol/l, respectively, p<0.001). Correction of thyrotoxicosis was obtained in all patients in both groups, but restoration of euthyroidism occurred earlier in SAT than in type 2 AIT (p=0.006). Ten type 2 AIT patients (17%) and 3 SAT patients (5%, p<0.03) became permanently hypothyroid after glucocorticoid withdrawal and required levothyroxine replacement.

CONCLUSIONS

A relevant proportion of type 2 AIT patients develop permanent hypothyroidism after correction of thyrotoxicosis. Thus, periodic surveillance of thyroid status is required after type 2 AIT.

Continuation of Amiodarone Therapy Despite Type II Amiodarone-Induced Thyrotoxicosis

BACKGROUND

Amiodarone is a powerful antiarrhythmic drug; however, its use may be complicated by thyrotoxicosis. When this occurs, clinicians must balance the continuation of amiodarone for antiarrhythmic purposes, and the discontinuation of treatment in order to prevent aggravation of the thyrotoxicosis. We studied the consequences of continuation or cessation of amiodarone in patients with type II amiodarone-induced thyrotoxicosis.

METHODS

Consecutive patients who developed type II amiodarone-induced thyrotoxicosis between September 1997 and September 2000 were studied. Amiodarone was continued in patients with previous ventricular arrhythmia or supraventricular arrhythmia associated with severe haemodynamic changes and was withdrawn in the other patients. In patients with persistent, severe symptomatic thyrotoxicosis, corticosteroids were added to therapy.

RESULTS

Thirteen patients were studied (nine with previous atrial fibrillation/flutter and four with ventricular tachycardia). Amiodarone treatment was continued in ten patients, including eight patients who received corticosteroids, and was temporarily halted in three patients. All patients recovered, with no difference in the duration of thyrotoxicosis between the two groups. Corticosteroid treatment was well tolerated and seemed to hasten the return to a euthyroid state (mean of 3.7 +/- 0.7 months vs 6.3 +/- 1.7 months). No recurrence of hyperthyroidism occurred during long-term follow-up.

CONCLUSION

In patients who require amiodarone, treatment may be safely continued despite the development of type II amiodarone-induced thyrotoxicosis.