Treatment of type II amiodarone-induced thyrotoxicosis by either iopanoic acid or glucocorticoids: a prospective, randomized study

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.

[Type 2 amiodarone-induced thyrotoxicosis: efficacy of glucocorticoid therapy, a retrospective analysis]

BACKGROUND

Type 2 amiodarone-induced thyrotoxicosis remains a significant problem of endocrinology and cardiology. Due to the increase a life expectancy of the population, the prevalence of cardiac arrhythmias and prescribing of amiodarone are increasing. Thyrotoxicosis aggravates the existing cardiovascular disease in patients, leads to the progression of left ventricular dysfunction, relapses of arrhythmias, increasing the risk of adverse outcomes. The tactic of further management of patients is complicated: it is necessary to resolve the issue of canceling or continuing the use of antiarrhythmic drugs necessary for a patient with a history of cardiac arrhythmia, as well as competent therapy of the thyroid pathology that has arisen. Oral glucocorticoids are the first-line drugs for the treatment of patients with moderate and severe type 2  amiodarone-induced thyrotoxicosis. Despite the appearance of clinical recommendations, opinions on the management of patients are differ, both among cardiologists and among endocrinologists. Often thyrostatics are prescribed to patients simultaneously with glucocorticoids, although it doesn't have pathogenetic basis.

AIM

To evaluate the efficacy of various therapy options in patients with type 2 amiodarone-induced thyrotoxicosis.

MATERIALS AND METHODS

The retrospective study included 38 patients (20 men and 18 women aged 35 to 85 years) with type 2 amiodarone-induced thyrotoxicosis. All patients underwent an analysis of anamnestic, anthropometric data, complex laboratory and instrumental diagnostics. According to the treatment options, 3 groups were retrospectively formed: without therapy (n=19), taking glucocorticoids (n=11) and combination of glucocorticoids and thyrostatics (n=8). The follow-up period was 6-18 months, including the treatment. The efficacy of treatment in the groups was evaluated by the time of reaching euthyroidism on the background of glucocorticoid therapy and duration of thyrotoxicosis; the search was conducted for potential predictors of delayed response to glucocorticoid therapy and long-term course of thyrotoxicosis.

RESULTS

The average age was 62.0 [52.9; 66.3] years. The level of free thyroxine was significantly decreased after 1 month from the start of therapy in both groups: from 38.1 [32.1; 58.4] to 23.4 [19.6; 29.3] pmol/l (p<0.001) in the group taking glucocorticoids; from 73.9 [42.2; 75.6] to 39.3 [22.4; 47.2] pmol/l (p<0.001) in the combination therapy group. The time of reaching euthyroidism was longer in the combination therapy group (p=0.047), didn't depend on the dose (p=0.338) and duration of taking thiamazole (p=0.911), the delayed response to therapy correlated with age (p=-0.857; p=0.007) and time interval from the appearance of clinical symptoms of thyrotoxicosis to the start of glucocorticoid therapy (p=0.881; p<0.001).

CONCLUSION

The results demonstrate the dependence of glucocorticoid response on the age of the patient and start time of therapy relative to the duration of thyrotoxicosis, inexpediency of additional prescribing thyrostatics in type 2 amiodarone-induced thyrotoxicosis.

Non-thionamide antithyroid drug options in Graves' hyperthyroidism

INTRODUCTION

The thionamide anti-thyroid drugs namely carbimazole, methimazole, and propylthiouracil, have been the predominant therapy modality for Graves' hyperthyroidism for over 60 years. Although these agents have proven efficacy and favorable side-effect profiles, non-thionamide alternatives are occasionally indicated in patients who are intolerant or unresponsive to thionamides alone. This review examines the available non-thionamide drug options for the control of Graves' hyperthyroidism and summarizes their clinical utility, efficacy, and limitations.

AREAS COVERED

We reviewed existing literature on mechanisms, therapeutic utility, and side-effect profiles of non-thionamide anti-thyroid drugs. Established non-thionamide agents act on various phases of the synthesis, release, and metabolism of thyroid hormones and comprise historical agents such as iodine compounds and potassium perchlorate as well as drug repurposing candidates like lithium, glucocorticoids, beta-blockers, and cholestyramine. Novel experimental agents in development target key players in Graves' disease pathogenesis including B-cell depletors (Rituximab), CD40 blockers (Iscalimab), TSH-receptor antagonists, blocking antibodies, and immune-modifying peptides.

EXPERT OPINION

Non-thionamide anti-thyroid drugs are useful alternatives in Graves' hyperthyroidism and more clinical trials are needed to establish their safety and long-term efficacy in hyperthyroidism control. Ultimately, the promise for a cure will lie in novel approaches that target the well-established immunopathogenesis of Graves' disease.

Early surgery: a favorable prognosticator in amiodarone-induced thyrotoxicosis-a single-center experience with 53 cases

Fewer than 100 cases of amiodarone-induced thyrotoxicosis (AIT) managed surgically have been reported worldwide. This study aims to assess the outcome of thyroidectomy under general anesthesia in a relatively large case series. A retrospective analysis of the clinical records of 53 patients who underwent thyroidectomy for AIT between 1995 and 2019 was conducted. There were 48 (90%) males and 5 females with an average age of 63.7 years. Type 1 and 2 AIT were present in 35 (66%) and 18 (34%) of patients, respectively. The mean preoperative ejection fraction (EF) was 45 ± 13%. Salvage surgery was performed in 6 (11%) patients due to decompensating heart failure and/or malignant arrhythmias. 35 (66%) patients underwent urgent surgery due to a predicted late response to medical therapy and/or the need to discontinue it. Elective surgery was performed in the remainder. A considerable improvement in mean EF occurred 12 months post-surgery (44% vs. 49%; p < 0.001). The overall survival rate following thyroidectomy was 96% at 12 months, and 83% at 5 years. No survival differences were observed based on systolic function. Cardiac-specific mortality was 11%, and these patients demonstrated a considerably shorter survival post-surgery compared to those who died of a non-cardiac cause (27 ± 18 vs. 77.5 ± 54 months; p < 0.05). Total thyroidectomy can be safely performed under general anesthesia despite severe cardiac disease. It considerably improves cardiac function and confers a survival advantage. Therefore, it should be considered early in the treatment plan of select cases.

Endocrine system dysfunction and chronic heart failure: a clinical perspective

Chronic heart failure (CHF) leads to an excess of urgent ambulatory visits, recurrent hospital admissions, morbidity, and mortality regardless of medical and non-medical management of the disease. This excess of risk may be attributable, at least in part, to comorbid conditions influencing the development and progression of CHF. In this perspective, the authors examined and described the most common endocrine disorders observed in patients with CHF, particularly in individuals with reduced ejection fraction, aiming to qualify the risks, quantify the epidemiological burden and discuss about the potential role of endocrine treatment. Thyroid dysfunction is commonly observed in patients with CHF, and sometimes it could be the consequence of certain medications (e.g., amiodarone). Male and female hypogonadism may also coexist in this clinical context, contributing to deteriorating the prognosis of these patients. Furthermore, growth hormone deficiency may affect the development of adult myocardium and predispose to CHF. Limited recommendation suggests to screen endocrine disorders in CHF patients, but it could be interesting to evaluate possible endocrine dysfunction in this setting, especially when a high suspicion coexists. Data referring to long-term safety and effectiveness of endocrine treatments in patients with CHF are limited, and their impact on several "hard" endpoints (such as hospital admission, all-cause, and cardiovascular mortality) are still poorly understood.

A review of species differences in the control of, and response to, chemical-induced thyroid hormone perturbations leading to thyroid cancer

This review summarises the current state of knowledge regarding the physiology and control of production of thyroid hormones, the effects of chemicals in perturbing their synthesis and release that result in thyroid cancer. It does not consider the potential neurodevelopmental consequences of low thyroid hormones. There are a number of known molecular initiating events (MIEs) that affect thyroid hormone synthesis in mammals and many chemicals are able to activate multiple MIEs simultaneously. AOP analysis of chemical-induced thyroid cancer in rodents has defined the key events that predispose to the development of rodent cancer and many of these will operate in humans under appropriate conditions, if they were exposed to high enough concentrations of the affecting chemicals. There are conditions however that, at the very least, would indicate significant quantitative differences in the sensitivity of humans to these effects, with rodents being considerably more sensitive to thyroid effects by virtue of differences in the biology, transport and control of thyroid hormones in these species as opposed to humans where turnover is appreciably lower and where serum transport of T4/T3 is different to that operating in rodents. There is heated debate around claimed qualitative differences between the rodent and human thyroid physiology, and significant reservations, both scientific and regulatory, still exist in terms of the potential neurodevelopmental consequences of low thyroid hormone levels at critical windows of time. In contrast, the situation for the chemical induction of thyroid cancer, through effects on thyroid hormone production and release, is less ambiguous with both theoretical, and actual data, showing clear dose-related thresholds for the key events predisposing to chemically induced thyroid cancer in rodents. In addition, qualitative differences in transport, and quantitative differences in half life, catabolism and turnover of thyroid hormones, exist that would not operate under normal situations in humans.

Evaluation and Treatment of Amiodarone-Induced Thyroid Disorders

Amiodarone is a class III antiarrhythmic drug containing 37% iodine by weight, with a structure similar to that of thyroid hormones. Deiodination of amiodarone releases large amounts of iodine that can impair thyroid function, causing either hypothyroidism or thyrotoxicosis in susceptible individuals reflecting ~20% of patients administered the drug. Not only the excess iodine, but also the amiodarone (or its metabolite, desethylamiodarone) itself may cause thyroid dysfunction by direct cytotoxicity on thyroid cells. We present an overview of the epidemiology and pathophysiology of amiodarone-induced thyroid disorders, with a focus on the various forms of clinical presentation and recommendations for personalized management of each form.

Thyroid Disorders and Prognosis in Chronic Heart Failure: A Long-Term Follow-Up Study

BACKGROUND

Thyroid disorders may have a negative impact on the prognosis of patients affected by chronic heart failure (CHF).

OBJECTIVE

The aim of the current study was to evaluate the prognostic role of all thyroid disorders over a long term follow-up in a single centre large sample of CHF outpatients.

METHODS

In all patients, the function of the thyroid was evaluated at the enrolment and during the follow- up. On the basis of free triiodothyronine (T3), free thyroxine (fT4) and thyroid-stimulating hormone (TSH) serum levels, patients were classified into one of the following four categories: euthyroid subjects, patients affected by hypothyroidism, low T3 (LT3) syndrome and hyperthyroidism. During the follow-up, death for all causes was assessed as primary end-point, whereas time to the first hospitalization for heart failure worsening was the secondary end-point analyzed.

RESULTS

Among 762 patients, 190 patients were affected by hypothyroidism (Hypo). LT3 syndrome was diagnosed in 15 patients and 59 patients were affected by hyperthyroidism (Hyper). During a long term follow-up (5.1±3.7 years), 303 patients died. Patients with Hypo showed an increased risk of death as well as of hospitalization due to heart failure worsening at univariate regression analysis. At multivariate regression analysis, Hypo remained associated with hospitalization after correction for age >75 years, ischemic aetiology, diabetes, therapy with ACE-inhibitors or ARBs, therapy with betablockers and with aldosterone antagonists, NYHA class 3, systolic arterial pressure <95 mmHg, left ventricular ejection fraction <30%, estimated glomerular filtration rate <60 ml/min, hyponatremia and NTproBNP> 1000 pg/ml. At multivariate analysis, the independent association with death was significant only for the subgroup of patients with TSH >10 mIU/L. LT3 was independently associated with both heart failure hospitalization and death, whereas Hyper was not associated with any of the two considered end-points.

CONCLUSION

Hypo is associated with a worse prognosis over a long-term follow-up. The association with heart failure hospitalization is not dependent on the baseline TSH levels, whereas the association with death is significant only when TSH >10 mIU/L. Finally, Hyper does not have any association with a worse prognosis.

Review of oral cholecystographic agents for the management of hyperthyroidism

OBJECTIVE

Although the use of oral cholecystographic agents (OCAs) had declined due to limited availability, there is literature to suggest it is an effective medication for thyrotoxicosis in appropriate clinical situations.

METHODS

The authors performed a PubMed search and systematically reviewed all the English written case reports, original studies and reviews from 1953 to 2012. Additional information was supplemented from available online pharmacologic databases.

RESULTS

The off-label use of OCAs was reviewed for the management of neonatal and adult Graves' disease, subacute thyroiditis, amiodarone-induced thyroiditis (AIT), exogenous hyperthyroidism, toxic multinodular goiter (TMNG), thyrotropinoma, thyrotoxicosis during pregnancy, rapid pre-operative control of hyperthyroidism, and thyroid storm. Adverse effects were also reviewed.

CONCLUSION

OCAs generally are effective agents in treating thyrotoxicosis in the etiologies reviewed. OCAs are clinically relevant in patients who require rapid control, such as in the pre-operative state or patient who cannot tolerate a thyrotoxicosis state. OCA may also be beneficial in situations where other anti-thyroidal medication would be hazardous or ineffective, such as thionamide allergy or exogenous thyrotoxicosis. Given concern for long-term relapse, OCAs should be considered a short-term bridge to definitive therapy. OCAs are limited in TMNG and should be second line after glucocorticoids in AIT II. OCAs do not preclude the use of radioactive iodine, which can be performed one week after OCA therapy.

[Clinical aspects of treatment with amiodarone]

Amiodarone has multiple and complex electrophysiological effects that render it a very effective antiarrhythmic drug for the treatment of both, supraventricular and ventricular arrhythmias. Proarrhythmic effects of amiodarone in patients with structural heart disease are rare. However, extracardiac adverse effects occurring in association with amiodarone treatment are frequent and feared. These adverse effects have usually been related to total amiodarone exposure (i. e., dose and duration of treatment). Parallel to a more frequent use of lower amiodarone maintenance doses (100-200 mg/day), the incidence of severe unwanted extracardiac side effects has decreased. High-dose maintenance regiments (daily dose ≥300 mg) are usually obsolete. This paper discusses recommendations regarding the monitoring of cardiac and extracardiac side effects of amiodarone. They need to be regarded by physicians using amiodarone to ensure long-term safety of amiodarone therapy.

2018 European Thyroid Association (ETA) Guidelines for the Management of Amiodarone-Associated Thyroid Dysfunction

Treatment with amiodarone is associated with changes in thyroid function tests, but also with thyroid dysfunction (amiodarone-induced hypothyroidism, AIH, and amiodarone-induced thyrotoxicosis, AIT). Both AIH and AIT may develop in apparently normal thyroid glands or in the presence of underlying thyroid abnormalities. AIH does not require amiodarone withdrawal, and is treated with levothyroxine replacement if overt, whereas subclinical forms may be followed without treatment. Two main types of AIT are recognized: type 1 AIT (AIT 1), a form of iodine-induced hyperthyroidism occurring in nodular goitres or latent Graves disease, and type 2 AIT (AIT 2), resulting from destructive thyroiditis in a normal thyroid gland. Mixed/indefinite forms exist due to both pathogenic mechanisms. AIT 1 is best treated with thionamides that may be combined for a few weeks with sodium perchlorate to make the thyroid gland more sensitive to thionamides. AIT 2 is treated with oral glucocorticoids. Once euthyroidism has been restored, AIT 2 patients are followed up without treatment, whereas AIT 1 patients should be treated with thyroidectomy or radioiodine. Mixed/indefinite forms of AIT are treated with thionamides. Oral glucocorticoids can be added from the beginning if a precise diagnosis is uncertain, or after a few weeks if response to thionamides alone is poor. The decision to continue or to stop amiodarone in AIT should be individualized in relation to cardiovascular risk stratification and taken jointly by specialist cardiologists and endocrinologists. In the presence of rapidly deteriorating cardiac conditions, emergency thyroidectomy may be required for all forms of AIT.

Dysthyroidism and Chronic Heart Failure: Pathophysiological Mechanisms and Therapeutic Approaches

Among comorbidity in chronic heart failure (CHF), dysthyroidism represents a relevant problem especially in the ageing CHF patients worldwide. Thyroid greatly affects many cardiovascular activities and its dysfunction may worsen a CHF condition. In particular, hypothyroidism has a relative high prevalence in patients with heart failure and it plays a key role in influencing CHF onset, progression and prognosis. Hyperthyroidism, is less frequent in this clinical context but it necessitates of immediate treatment because of its negative effects on cardiovascular balance. Also, it must be considered that dysthyroism may also be iatrogenic and the main responsible drug is Amiodarone.Based on the best available evidence and our cumulative clinical experience, this manuscript analyzes the prevalence, the pathophysiology and the prognostic impact of thyroid disorders in chronic heart failure.

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.

Current trends in antithyroid drug treatment of Graves' disease

INTRODUCTION

Graves' hyperthyroidism is associated with significant morbidity and mortality risk. The thionamides, methimazole, its pro-drug derivative carbimazole, and propylthiouracil, remain a cornerstone of management. Yet despite decades of use, optimal strategies for maximising treatment response and curtailing adverse effect risk remains uncertain.

AREAS COVERED

We reviewed the current literature on the evidence based medical management of Graves' disease. Specifically, we evaluated current approaches to the use of thionamides, adjunctive therapies, and potential novel agents for controlling Graves' hyperthyroidism.

EXPERT OPINION

Primary medical therapy is successful in less than 50% of cases and so careful selection of patients for medical treatment based on a combination of pathological and pragmatic considerations is essential. Carbimazole or methimazole is the treatment of choice in the non-pregnant population driven by its more favourable pharmacokinetic and adverse effect profile over propylthiouracil. In pregnancy the choice of treatment is less straightforward and an approach that minimises undue fetal exposure to all thionamides should be adopted. Additional data is needed on the value of adjunctive therapies including potassium perchlorate, iodides, glucocorticoids, lithium, and cholestyramine. Novel agents directed against pathogenetic targets including TSH receptor blocking monoclonal antibodies and small molecule antagonists may hold promise for the future.

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.

Thyroid Disease and the Heart

Thyroid hormones have an intimate relationship with cardiac function. Some of the most significant clinical signs and symptoms of thyroid disease are the cardiac manifestations. In both hypothyroidism and hyperthyroidism, the characteristic physiological effects of thyroid hormone can be understood from the actions at the molecular and cellular level. Here we explore topics from the metabolism and cellular effects of thyroid hormone to special considerations related to statin and amiodarone therapy for the alterations in thyroid hormone metabolism that accompany heart disease.

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.

Hyperthyroidism and thyrotoxicosis

Hyperthyroidism and thyrotoxicosis are hypermetabolic conditions that cause significant morbidity and mortality. The diagnosis can be difficult because symptoms can mimic many other disease states leading to inaccurate or untimely diagnoses and management. Thyroid storm is the most severe form of thyrotoxicosis, hallmarked by altered sensorium, and, if untreated, is associated with significant mortality. Thyroid storm should be considered in the differential of any patient presenting with altered mental status. The emergency medicine physician who can rapidly recognize thyrotoxicosis, identify the precipitating event, appropriately and comprehensively begin medical management, and facilitate disposition will undoubtedly save a life.

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.

Thyroid hormone and the cardiovascular system

Thyroid hormone has profound effects on the heart and cardiovascular system. This article describes the cellular mechanisms by which thyroid hormone acts at the level of the cardiac myocyte and the vascular smooth muscle cell to alter phenotype and physiology. Because it is well established that thyroid hormone, specifically T(3), acts on almost every cell and organ in the body, studies on the regulation of thyroid hormone transport into cardiac and vascular tissue have added clinical significance. The characteristic changes in cardiovascular hemodynamics and metabolism that accompany thyroid disease states can then be best understood at the cellular level.

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.

Acute thyrotoxicosis secondary to destructive thyroiditis associated with cardiac catheterization contrast dye

BACKGROUND

Thyrotoxicosis caused by destructive thyroiditis is self-limited and results from the subacute release of preformed thyroid hormone. Common etiologies include painful subacute thyroiditis and silent (painless) subacute thyroiditis (including postpartum thyroiditis, amiodarone-associated destructive thyroiditis, and lithium-associated thyroiditis). Thyrotoxicosis commonly evolves slowly over a matter of weeks.

PATIENT FINDINGS

We report a unique case of severe thyrotoxicosis caused by acute- onset painful destructive thyroiditis in a patient who received large amounts of nonionic contrast dye Hexabrix® for cardiac catheterization. The results of thyroid function and physical examination were normal before the catheterization.

SUMMARY

The acute onset of severe thyroid pain, rapid increase in serum Free Thyroxine Index, and thyroglobulin concentrations with a triiodothyronine to free thyroxine index ratio of < 20 to 1 were compatible with an acute onset destructive thyroiditis, likely related to direct toxicity from the iodinated contrast material.

CONCLUSIONS

In light of the large number of patients who receive these contrast agents during cardiac catheterization, clinicians should be advised of this potentially serious complication, particularly in the setting of unstable cardiac disease.

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.

Amiodarone and thyroid

Assessment of TSH and TPO-Ab before starting amiodarone (AM) treatment is recommended. The usefulness of periodic TSH measurement every 6 months during AM treatment is limited by the often sudden explosive onset of AIT, and the spontaneous return of a suppressed TSH to normal values in half of the cases. AM-induced hypothyroidism develops rather early after starting treatment, preferentially in iodine-sufficient areas and in females with TPO-Ab; it is due to failure to escape from the Wolff-Chaikoff effect, resulting in preserved radioiodine uptake. AM-induced thyrotoxicosis (AIT) occurs at any time during treatment, preferentially in iodine-deficient regions and in males. AIT can be classified in type 1 (iodide-induced thyrotoxicosis, best treated by potassium perchlorate in combination with thionamides and discontinuation of AM) and type 2 (destructive thyrotoxicosis, best treated by prednisone; discontinuation of AM may not be necessary). AIT is associated with a higher rate of major adverse cardiovascular events (especially of ventricular arrhythmias). Uncertainty continues to exist with respect to the feasibility of continuation of AM despite AIT, the appropriate methods to distinguish between AIT type 1 and 2 as well as the advantages of AIT classification into subtypes in view of possible mixed cases, and the best policy when AM needs to be restarted.

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.

Pharmacodynamic Effect of Iopanoic Acid on Free T3 and T4 Levels in Amiodarone-induced Thyrotoxicosis

We describe the effects of iopanoic acid on daily levels of free triiodothyronine (FT3) and free thyroxine (FT4) in a patient with progressive type II amiodarone-induced thyrotoxicosis (AIT) who was undergoing thyroidectomy. The patient was a 59-year-old man who was undergoing amiodarone therapy while awaiting cardiac transplantation; the use of beta blockers and corticosteroids to control the AIT was contraindicated in this patient. Prior to thyroidectomy, the patient was started on iopanoic acid at 1.0 g twice a day; in response to gastrointestinal side effects, the dosage was subsequently reduced to 0.5 g twice a day. The patient responded to iopanoic acid with a rapid decrease in his FT3 level and slight increase in his FT4 level. This control of thyrotoxicosis allowed for an uneventful thyroidectomy, which was later followed by successful cardiac transplantation. Based on our findings in this single case, we believe that iopanoic can be used to rapidly lower FT3 levels and to treat symptoms of thyrotoxicosis in a preoperative setting. We also discuss the different pharmacodynamic effects that iopanoic acid has on FT3 and FT4 levels.

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.

Palpation thyroiditis causing new-onset atrial fibrillation

OBJECTIVE

Surgery-induced thyroiditis can pose a significant clinical problem that is underappreciated. We present a case of new-onset atrial fibrillation as a consequence of palpation thyroiditis in a 70-year-old man who underwent radical right neck dissection for malignant melanoma and review the limited literature on this topic.

DESIGN

Biochemical parameters including thyrotropin, free thyroxine, triiodothyronine, erythrocyte sedimentation rate, C-reactive protein, thyroglobulin, thyroid stimulating immunoglobulins, thyroid binding inhibitory immunoglobulins, thyroid peroxidase, thyroglobulin antibodies, and 24-hour urine iodine were measured. Thyroid ultrasound and technetium-99m pertechnetate scintigraphy with radioactive iodine 131 uptake were employed for diagnostic purposes.

MAIN OUTCOME

Following right neck exploratory dissection, the patient developed hyperthyroidism and atrial fibrillation. Imaging studies were compatible with right lobar thyroiditis. Other etiologies of thyroiditis were excluded. Despite normalization of thyroid function after 2 weeks, atrial fibrillation persisted and required cardioversion.

CONCLUSIONS

Manipulation of the thyroid gland during neck exploratory surgery can result in hyperthyroidism with atrial fibrillation as a consequence. To avoid this complication, careful attention should be paid during surgical procedures or other clinical situations in which the thyroid gland is manipulated.

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.

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.

Amiodarone-induced thyrotoxicosis: clinical course and predictors of outcome

OBJECTIVES

This study sought to determine the clinical course and predictors of long-term outcome in patients with documented amiodarone-induced thyrotoxicosis (AIT).

BACKGROUND

Amiodarone-induced thyrotoxicosis is a condition that is difficult to manage, in particular because of the long half-life of amiodarone. Data on optimal treatment for AIT are scarce.

METHODS

We performed a retrospective review among patients with documented AIT at a tertiary care center. Baseline characteristics, treatment received, laboratory parameters, and events during follow-up were evaluated. The predefined composite end point consisted of the following AIT-associated complications: death, heart transplantation, hospitalization for heart failure, myocardial infarction, stroke, hospitalization for arrhythmia management, or hospitalization for treatment complications.

RESULTS

Eighty-four patients were included in the present analysis; 27 patients received prednisone for AIT. There was no difference in time to normalization of free thyroxine between those receiving and those not receiving prednisone. Long-term follow-up showed high morbidity and mortality; 47 patients (56%) reached the primary end point. Patients receiving prednisone had a worse outcome than those not receiving prednisone (p = 0.003). Although patients received prednisone for 84 +/- 65 days, curves started to separate only 12 months after the initial diagnosis.

CONCLUSIONS

Patients with AIT have a high event rate during follow-up. Prednisone had no effect on time to normalization of thyroxine levels and was associated with an increased event rate. Importantly, AIT-related problems must be expected late, at a time when thyroid function is under control.

Glucocorticoid receptor subunit gene expression in thyroid gland and adenomas

The present study was undertaken to investigate whether the glucocorticoid receptor -alpha (GR-alpha) and -beta (GR-beta) mRNA may be expressed in thyroid gland. Ten normal thyroid gland and 14 follicular adenomas were studied using a real-time fluorescent quantitative RT-PCR (FQ-RT-PCR) method. The results demonstrated that there was a lower expression of GR-alpha mRNA (x10(6) GR-alpha cDNA copies/microg total RNA) in thyroid adenoma (1.27+/-0.26) than that in normal thyroid gland (3.53+/-1.22) (p < 0.001). The expression of GR-beta mRNA was lower in all the thyroid tissues. Of note, there was a significant difference in GR-beta mRNA expression (x10(4) GR-beta cDNA copies/microg total RNA) between thyroid adenoma (80.8+/-13.9) and thyroid gland (1.78+/-0.59) (p < 0.001). The GR-alpha/GR-beta ratios in thyroid adenoma and normal thyroid gland were 1.67+/-0.68 and 207.57+/-84.41 respectively (p < 0.001). These results revealed, for the first time, that both GR-alpha and GR-beta mRNA expression were detectable in both thyroid gland and adenomas tissues. We therefore conclude that down-regulation of GR-alpha and up-regulation of GR-beta mRNA expression may play an important role in the thyroid adenomas.

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.

Mild and short recurrence of type II amiodarone-induced thyrotoxicosis in three patients receiving amiodarone continuously for more than 10 years

Although there are two types of amiodarone-induced thyrotoxicosis (AIT), only type II AIT has been seen at our institution in Japan so far. There have been few case reports of AIT recurrence, probably because of the fact that amiodarone is immediately discontinued once AIT has developed. Our own policy is not to discontinue amiodarone in all AIT patients, unless severe adverse effects such as pulmonary fibrosis develop. Among more than 50 patients with type II AIT we have encountered, three with arrhythmogenic right ventricular cardiomyopathy showed AIT recurrence. In these patients, the first episode of AIT developed 3, 4, and 2 years after the start of amiodarone administration, and recurrence was observed 5, 6, and 8 years after the first episode, respectively. The AIT resolved spontaneously in all cases while the patients continued to take amiodarone. In comparison with the first AIT episode, the second was milder and resolved within a shorter period. These three cases suggest that recurrence of type II AIT may not be rare in iodine-sufficient areas, and that it is relatively mild and may resolve spontaneously. Furthermore, at least in Japan, it may be possible for patients with recurrent type II AIT to continue taking amiodarone.

Amiodarone and the thyroid

Among the drugs affecting the thyroid gland, no drug has puzzled, and at the same time fascinated, endocrinologists more than amiodarone. Amiodarone is a potent class III anti-arrhythmic drug that also possesses beta-blocking properties. It is very rich in iodine, with a 100-mg tablet containing an amount of iodine that is 250 times the recommended daily iodine requirement. Amiodarone produces characteristic alterations in thyroid function tests in euthyroid patients. Understanding these alterations is crucial in avoiding unnecessary investigations and treatment. Amiodarone-induced thyroid dysfunction occurs because of both its iodine content and the direct toxic effects of the compound on thyroid parenchyma. Amiodarone-induced hyperthyroidism is more common in iodine-deficient regions of the world, whereas amiodarone-induced hypothyroidism is usually seen in iodine-sufficient areas. In contrast to amiodarone-induced hypothyroidism, amiodarone-induced thyrotoxicosis is a difficult condition to diagnose and treat. In this review, we discuss the alterations in thyroid function tests seen in euthyroid subjects, the epidemiology and mechanism of amiodarone-induced thyroid dysfunction, treatment options available, and the consequences of amiodarone use in pregnancy and lactation; and finally, we propose a follow-up strategy in patients taking amiodarone.

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

OBJECTIVE

To determine how expert European thyroidologists assess and treat amiodarone-induced thyrotoxicosis (AIT).

DESIGN

Members of the European Thyroid Association (ETA) with clinical interests were asked to answer a questionnaire on the diagnosis and management of AIT. A total of 124 responses were received: 116 from Europe, seven from USA and one from Brazil. After excluding responses coming from the same centre, 101 responses from 24 European countries were analysed, representing approximately 65% of clinically active European ETA members.

RESULTS

The majority of respondents (68%) see 1-10 new cases of AIT/year, and AIT seems to be more frequent than amiodarone-induced hypothyroidism in Europe, where in many instances iodine intake is borderline or moderately deficient. A good collaboration with cardiologists exists in most centres, and patients receiving chronic amiodarone treatment are checked for thyroid function most commonly every 4-6 months. When AIT is suspected, a diffuse or nodular goitre is present or in the absence of apparent abnormalities of the thyroid, free thyroxine (FT4), free triiodothyronine (FT3) and TSH are assayed by almost 90% of respondents. Thyroid autoimmunity is evaluated in the initial assessment by > 80%, while evaluation of urinary iodine excretion is unhelpful for > 60%. Most commonly used additional diagnostic procedures include thyroid ultrasonography, particularly colour flow Doppler sonography, and, to a lesser extent, a thyroid uptake scan. If the thyroid gland is apparently normal, measurement of thyroidal radioactive iodine uptake is considered useful by a large proportion of respondents to establish the destructive nature of the process. Differentiation of type I and type II AIT is difficult and, possibly, not correct for 27% of respondents, who believe that mixed (or indefinite) forms are probably more frequent than previously recognized. Approximately 10-20% do not consider amiodarone withdrawal necessary in the therapeutic strategy of AIT, especially if the thyroid gland is apparently normal. Most respondents (82%) treat type I AIT with thionamides, either alone (51%) or in combination with potassium perchlorate (31%), while the preferred treatment for type II AIT is represented by glucocorticoids (46%). Some respondents, in view of diagnostic difficulties, initially treat all cases of AIT with a combination of thionamides and glucocorticoids. After restoration of euthyroidism, ablative therapy is recommended by 34% in type I and only 8% in type II AIT. If amiodarone therapy needs to be reinstituted, prophylactic thyroid ablation is recommended by 65% in type I AIT, while a wait-and-see strategy is adopted by 70% in type II AIT.

CONCLUSION

Areas of certainty and uncertainty concerning AIT are present among expert European thyroidologists, both from a diagnostic and a therapeutic standpoint. Diagnostic criteria need to be refined in order to improve therapeutic outcome.

Hyperthyroidism: advantages and disadvantages of medical therapy

The most common causes of hyperthyroidism are Graves' disease, toxic nodular goiter, and iodine-induced hyperthyroidism. Hyperthyroidism can be treated medically with antithyroid drugs or radioactive iodine, or surgically. Multiple clinical factors must be weighed when choosing a treatment modality. All of the available forms of therapy have advantages and disadvantages, and treatment choices must be individualized.

Heterogeneity of amiodarone-induced thyrotoxicosis: evaluation of colour-flow Doppler sonography in predicting therapeutic response

BACKGROUND

Amiodarone-induced thyrotoxicosis (AIT) presents a therapeutic challenge because of its resistance to standard antithyroid therapy. In iodine-deplete environments, colour-flow Doppler sonography (CFDS) has allowed distinction between two types of AIT: (i) Type I AIT, associated with increased vascularity (CFDS I-III) and response to thionamide antithyroid drug and (ii) type II AIT, with no/little thyroid vascularity (CFDS 0) and prednisolone responsiveness.

AIM

To clarify if CFDS patterns correlated with treatment outcomes in a retrospective study of 24 patients with AIT in an iodine-replete environment.

METHODS

Medical records of patients who presented to a teaching hospital between January 1998 to December 2000 were reviewed. Results of CFDS, ultrasound measurement of thyroid size and technetium scanning of the thyroid were correlated with treatment responses, especially prednisolone responsiveness.

RESULTS

Thirteen of 24 patients showed CFDS 0. Twelve of these 13 were evaluable for prednisolone responsiveness, of whom seven (58%) were prednisolone-responsive. Of 11 patients with CFDS I-III, four (36%) responded to antithyroid medication alone and only one of seven (14%) was prednisolone-responsive. Euthyroidism was achieved twice as rapidly in patients with CFDS 0 than those with CFDS I-III. Because of medical treatment failure, seven patients, from both CFDS groups, required urgent near-total thyroidectomy which was successful and uncomplicated in all cases.

CONCLUSIONS

CFDS is useful in the management of AIT because CFDS 0 correlates better with prednisolone response (58%) than CFDS I-III (14%). However, unlike experience in iodine-deficient regions, the results of the present study revealed that treatment responses to thionamide or prednisolone were heterogeneous within uniform CFDS patterns. Thus, prednisolone--responsiveness was not consistently predicted by CFDS 0, but the presence of flow appeared to correlate with non-response to prednisolone.

Can amiodarone be restarted after amiodarone-induced thyrotoxicosis?

Thyrotoxicosis is a well-documented and studied complication of treatment with amiodarone, but little has been written about the risks and treatment of recurrent thyrotoxicosis upon re-exposure to amiodarone. One such case is outlined here and discussed by a panel of experts.

Is there a place for thyroidectomy in older patients with thyrotoxic storm and cardiorespiratory failure?

Early thyroidectomy is the treatment of choice for thyrotoxic storm in patients with thyroid autonomy often induced by iodine. However, older patients who are mostly affected by this condition often have underlying chronic cardiopulmonary diseases, apparently contradicting surgical intervention. The published evidence for suitable treatment strategies in these patients is limited. We report the outcome of a series of older critically ill patients who were treated by thyroidectomy because of thyrotoxic storm. We retrospectively analyzed the outcome of 10 patients (4 males, 6 females; 70 years of age, range, 54-79, Burch-Wartofsky point scale, 61; range, 40-85) with thyrotoxic storm, thyroid autonomy, and severe cardiorespiratory and renal failure with cardiac arrhythmia, coronary artery or chronic obstructive pulmonary disease, or acute inflammation. Thyroidectomy was performed for the following reasons: symptoms of thyrotoxic storm deteriorated or did not improve within 24-48 hours despite intensive medical treatment, or patients developed thionamide-induced agranulocytosis or severe thrombocytopenia. All patients with severe accompanying diseases survived thyroidectomy (early post-operative mortality, 0%). The two oldest patients died 2-3 weeks after thyroidectomy because of myocardial infarction or respiratory failure (late postoperative mortality, 20%). In contrast, in the few previous reports of patients who underwent thyroidectomy for thyrotoxic storm and severe accompanying diseases (n = 7), late postoperative mortality was 43%. The overall mortality for all reported patients including our own, who underwent thyroidectomy for thyrotoxic storm with and without severe accompanying disease (n = 49) was 10%. Our results suggest that early total thyroidectomy should be considered as the method of choice for older, chronically ill patients with thyrotoxic storm complicated by cardiorespiratory and renal failure, especially if high-dose thionamide treatment, iopanoic acid, glucocorticoids, and intensive care fail to improve the patient's conditions within 12-24 hours.

The prevalence of elevated serum C-reactive protein levels in inflammatory and noninflammatory thyroid disease

C-reactive protein (CRP) levels have not been routinely used to diagnose thyroid disease, although many thyroid conditions involve inflammation. This study was intended to determine whether CRP levels could differentiate between inflammatory and noninflammatory thyroid conditions, especially between type II inflammatory amiodarone-induced thyrotoxicosis (AIT) and type I iodine-induced AIT. Serum high-sensitivity CRP levels were measured in 100 euthyroid controls (7 taking amiodarone) and 353 patients with one of the following thyroid conditions: AIT, subacute thyroiditis, toxic diffuse goiter, nodular goiter, Hashimoto's thyroiditis, shortterm hypothyroidism, or postpartum thyroiditis. No patients with nontoxic multinodular goiter (n = 34), toxic nodular goiter (n = 23), or toxic diffuse goiter, either untreated (n = 49) or euthyroid while taking methimazole (n = 33), had positive CRP levels (>10 mg/L). The occurrence of positive CRP levels among patients with Hashimoto's thyroiditis (n = 35), short-term hypothyroidism (n = 38), and postpartum thyroiditis (n = 70) did not differ significantly from controls. The occurrence of positive CRP values did not differ significantly between patients with type I and type II AIT and controls. Six of 7 patients (86%) with untreated subacute thyroiditis had positive CRP levels (p < 0.00001). These results indicate that there is only a limited role for measurement of CRP levels in the diagnosis of thyroid diseases other than subacute thyroiditis.