Risk factors for amiodarone-induced thyroid dysfunction in Japan

Evaluation of the prevalence and laboratory test results of overt thyrotoxicosis cases

BACKGROUND

The frequency of thyrotoxicosis may vary between countries and some laboratory test results may be used in etiology research. This study aimed to evaluate the prevalence of thyrotoxicosis diagnoses and laboratory test results.

METHODS

3246 patients with overt thyrotoxicosis were included in this study. Laboratory test results, epicrisis, thyroid ultrasonography, thyroid scintigraphy, and radioactive iodine uptake test reports of the patients were examined in the study.

RESULTS

Thyrotoxicosis was found due to levothyroxine overdose in 58.1% of the patients. When this group was excluded, 36.1% of the patients were diagnosed with toxic multinodular goiter most frequently. TRab levels were 8.5 times higher in Graves' disease than in other diagnostic groups. Anti-TPO levels were found to be the highest in the Graves' disease and Hashitoxicosis groups compared to other diagnostic groups (p<0.001). Anti-Tg levels were found to be highest in Graves' disease, Postpartum thyroiditis, and Hashitoxicosis patients (p<0.001). The free triiodothyronine / free thyroxine ratio was significantly higher, a cut-off value of >2.94 provided a sensitivity of 66% and specificity of 64% in diagnosing Graves' disease.

CONCLUSION

The causes of thyrotoxicosis show some differences between countries. Patients using levothyroxine should be informed about drug use and dose titration. The free triiodothyronine / free thyroxine ratio can be used in addition to other tests during diagnosis.

Monitoring thyroid function during amiodarone use

Amiodarone is an antiarrhythmic drug used to treat cardiac tachyarrhythmias. It has many adverse effects, with thyroid dysfunction one of the most notable. Through various mechanisms, both thyrotoxicosis and hypothyroidism can occur secondary to amiodarone therapy. There are two types of amiodarone-induced thyrotoxicosis: type 1 occurs in those with pre-existing thyroid disease and is treated with thionamide, whereas type 2 occurs in those without and is treated with glucocorticoids. Patients with amiodarone-induced hypothyroidism may be given levothyroxine to replace thyroid hormone, but in some cases, the appropriate management may be cessation of amiodarone.

[Type 2 amiodarone-induced thyrotoxicosis: prevalence, time and predictors of development]

BACKGROUND

Amiodarone takes a leading position in arrhythmological practice in the prevention and relief of various cardiac arrhythmias. Type 2 amiodarone-induced thyrotoxicosis is a frequent side effect of the drug. It is the most complex type of thyroid dysfunction both in terms of the severity of clinical manifestations, and in terms of understanding the mechanisms of pathogenesis, possibility of differential diagnosis and providing effective treatment. Due to the increasing life expectancy of the population, corresponding increase in the frequency of cardiac arrhythmias, the problem does not lose its relevance. Identification of predictors, assessment and prediction of the individual risk of developing this thyroid pathology is a necessity in daily clinical practice for making a reasonable decision when prescribing the drug, determining the algorithm for further dynamic monitoring of the patient.

AIM

To evaluate the structure of amiodarone-induced thyroid dysfunction, prevalence, time and predictors of development type 2 amiodarone-induced thyrotoxicosis in a prospective cohort study. MATERIALS AND METHODS: The study involved 124 patients without thyroid dysfunction who received amiodarone therapy for the first time. Evaluation of the functional state of the thyroid gland was performed initially, after prescribing the drug for the first 3 months 1 time per month, in the future - every 3 months. The follow-up period averaged 12-24 months. The end of the observation occurred with the development of amiodaron-induced thyroid dysfunction or patient's refusal to further participate in the study. For the differential diagnosis of the type of amiodarone-induced thyrotoxicosis, the level of anti-TSH receptor antibodies and thyroid scintigraphy with technetium pertechnetate were determined. The type and frequency of thyroid dysfunction, time and predictors of development type 2 amiodarone-induced thyrotoxicosis were evaluated.

RESULTS

The structure of amiodarone-induced thyroid dysfunction was represented by hypothyroidism in 19,3% (n=24), type 1 thyrotoxicosis in 1,6% (n=2), type 2 thyrotoxicosis in 23,4% (n=29). The median time of its development was 92,0 [69,0;116,0] weeks; the average period of common survival - 150,2±12,6 weeks (95% CI: 125,5-175,0), median - 144±21,7 weeks (95% CI: 101,4-186,6). The main predictors of type 2 amiodarone-induced thyrotoxicosis were: age (OR=0,931; 95% CI: 0,895-0,968; p<0.001), BMI (OR=0,859; 95% CI: 0,762-0,967; p=0,012), time from the start of amiodarone therapy (OR=1,023; 95% CI: 1,008-1,038; p=0,003). Age ≤60 years was associated with increased risk of the dysfunction by 2.4 times (OR=2,352; 95% CI: 1,053-5,253; p=0,037), BMI≤26,6 kg/m2 - 2,3 times (OR=2,301; 95% CI: 1,025-5,165; p=0,043). CONCLUSION: The results allow to personalized estimate the risk of type 2 amiodarone-induced thyrotoxicosis and determine the patient's management tactic.

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.

Single and joint toxic effects of thyroid hormone, levothyroxine, and amiodarone on embryo-larval stages of zebrafish (Danio rerio)

This study evaluates single and joint endocrine disruptor toxicities of thyroid hormone, levothyroxine, and amiodarone in the embryo-larval stages of Danio rerio. Single toxicity experiments were carried out in concentrations based on the environmental concentration and increasing concentrations of 10, 100, and 1000 times the environmental concentration. Joint toxicity experiments evaluated the combined effects of these compounds. Toxic effects were examined during zebrafish embryonic development, and the parameters analyzed were apical sublethal, teratogenicity, mortality endpoints, and morphometry. Thyroid hormone exhibited the highest toxicity. However, the results showed that the environmental concentrations for all 3 compounds had low risk in relation to the parameters studied, such as teratogenic effects and morphometry. The larvae were more affected than embryos, where embryos needed higher concentrations in all experiments, possibly due to the absence of the chorion. The same type of effects were observed in the joint toxicity test, except that a possible antagonistic effect was detected. However, high concentrations showed stronger effects of these toxic compounds on fish development.

Explainable Machine Learning Techniques To Predict Amiodarone-Induced Thyroid Dysfunction Risk: Multicenter, Retrospective Study With External Validation

BACKGROUND

Machine learning offers new solutions for predicting life-threatening, unpredictable amiodarone-induced thyroid dysfunction. Traditional regression approaches for adverse-effect prediction without time-series consideration of features have yielded suboptimal predictions. Machine learning algorithms with multiple data sets at different time points may generate better performance in predicting adverse effects.

OBJECTIVE

We aimed to develop and validate machine learning models for forecasting individualized amiodarone-induced thyroid dysfunction risk and to optimize a machine learning-based risk stratification scheme with a resampling method and readjustment of the clinically derived decision thresholds.

METHODS

This study developed machine learning models using multicenter, delinked electronic health records. It included patients receiving amiodarone from January 2013 to December 2017. The training set was composed of data from Taipei Medical University Hospital and Wan Fang Hospital, while data from Taipei Medical University Shuang Ho Hospital were used as the external test set. The study collected stationary features at baseline and dynamic features at the first, second, third, sixth, ninth, 12th, 15th, 18th, and 21st months after amiodarone initiation. We used 16 machine learning models, including extreme gradient boosting, adaptive boosting, k-nearest neighbor, and logistic regression models, along with an original resampling method and 3 other resampling methods, including oversampling with the borderline-synthesized minority oversampling technique, undersampling-edited nearest neighbor, and over- and undersampling hybrid methods. The model performance was compared based on accuracy; Precision, recall, F₁-score, geometric mean, area under the curve of the receiver operating characteristic curve (AUROC), and the area under the precision-recall curve (AUPRC). Feature importance was determined by the best model. The decision threshold was readjusted to identify the best cutoff value and a Kaplan-Meier survival analysis was performed.

RESULTS

The training set contained 4075 patients from Taipei Medical University Hospital and Wan Fang Hospital, of whom 583 (14.3%) developed amiodarone-induced thyroid dysfunction, while the external test set included 2422 patients from Taipei Medical University Shuang Ho Hospital, of whom 275 (11.4%) developed amiodarone-induced thyroid dysfunction. The extreme gradient boosting oversampling machine learning model demonstrated the best predictive outcomes among all 16 models. The accuracy; Precision, recall, F₁-score, G-mean, AUPRC, and AUROC were 0.923, 0.632, 0.756, 0.688, 0.845, 0.751, and 0.934, respectively. After readjusting the cutoff, the best value was 0.627, and the F₁-score reached 0.699. The best threshold was able to classify 286 of 2422 patients (11.8%) as high-risk subjects, among which 275 were true-positive patients in the testing set. A shorter treatment duration; higher levels of thyroid-stimulating hormone and high-density lipoprotein cholesterol; and lower levels of free thyroxin, alkaline phosphatase, and low-density lipoprotein were the most important features.

CONCLUSIONS

Machine learning models combined with resampling methods can predict amiodarone-induced thyroid dysfunction and serve as a support tool for individualized risk prediction and clinical decision support.

Incidence of thyroid dysfunction following initiation of amiodarone treatment in patients with and without heart failure: a nationwide cohort study

AIMS

Thyroid dysfunction is considered the most frequent complication to amiodarone treatment, but data on its occurrence outside clinical trials are sparse. The present study aimed to examine the incidence of thyroid dysfunction following initiation of amiodarone treatment in a nationwide cohort of patients with and without heart failure (HF).

METHODS AND RESULTS

In Danish registries, we identified all patients with first-time amiodarone treatment during the period 2000-18, without prior thyroid disease or medication. The primary outcome was a composite of thyroid diagnoses and initiation of thyroid drugs. Outcomes were assessed at 1-year follow-up, and for patients free of events in the first year, in a landmark analysis for the subsequent 5 years. We included 43 724 patients with first-time amiodarone treatment, of whom 16 939 (38%) had HF. At 1-year follow-up, the cumulative incidence and adjusted hazard ratio (HR) of the primary outcome were 5.3% and 1.37 (95% confidence interval 1.25-1.50) in patients with a history of HF and 4.2% in those without HF (reference). In the 1-year landmark analysis, the subsequent 5-year cumulative incidences and adjusted HRs of the primary outcome were 5.3% (reference) in patients with 1-year accumulated dose <27.38 g [corresponding to average daily dose (ADD <75 mg)], 14.0% and HR 2.74 (2.46-3.05) for 27.38-45.63 g (ADD 75-125 mg), 20.0% and HR 4.16 (3.77-4.59) for 45.64-63.88 g (ADD 126-175 mg), and 24.5% and HR 5.30 (4.82-5.90) for >63.88 g (ADD >175 mg).

CONCLUSION

Among patients who initiated amiodarone treatment, around 5% had thyroid dysfunction at 1-year follow-up, with a slightly higher incidence in those with HF. A dose-response relationship was observed between the 1-year accumulated amiodarone dose and the subsequent 5-year cumulative incidence of thyroid dysfunction.

AMIODARONE AND THYROID DYSFUNCTION

Thyroid gland has a key role in maintaining the body homeostasis. Thyroxine is the main hormone secreted from the thyroid gland, its effect being predominantly achieved after the intracellular conversion of thyroxine to triiodothyronine, which exhibits a higher affinity for the receptor complex, thus modifying gene expression of the target cells. Amiodarone is one of the most commonly used antiarrhythmics in the treatment of a broad spectrum of arrhythmias, usually tachyarrhythmias. Amiodarone contains a large proportion of iodine, which is, in addition to the intrinsic effect of the medication, the basis of the impact on thyroid function. It is believed that 15%-20% of patients treated with amiodarone develop some form of thyroid dysfunction. Amiodarone may cause amiodarone-induced hypothyroidism (AIH) or amiodarone-induced thyrotoxicosis (AIT). AIT is usually developed in the areas with too low uptake of iodine, while AIH is developed in the areas where there is a sufficient iodine uptake. Type 1 AIT is more common among patients with an underlying thyroid pathology, such as nodular goiter or Graves' (Basedow's) disease, while type 2 mostly develops in a previously healthy thyroid. AIH is more common in patients with previously diagnosed Hashimoto's thyroiditis. Combined types of the diseases have also been described. Patients treated with amiodarone should be monitored regularly, including laboratory testing and clinical examinations, to early detect any deviations in the functioning of the thyroid gland. Supplementary levothyroxine therapy is the basis of AIH treatment. In such cases, amiodarone therapy quite often need not be discontinued. Type 1 AIT is treated with thyrostatic agents, like any other type of thyrotoxicosis. If possible, the underlying amiodarone therapy should be discontinued. In contrast to type 1 AIT, the basic pathophysiological substrate of which is the increased synthesis and release of thyroid hormones, the basis of type 2 AIT is destructive thyroiditis caused by amiodarone, desethylamiodarone as its main metabolite, and an increased iodine uptake. Glucocorticoid therapy is the basis of treatment for this type of disease.

Update on subclinical thyroid dysfunction

Subclinical thyroid dysfunction is defined by serum thyroid-stimulating hormone (TSH) levels either greater or less than the reference range with normal thyroxine (T4) concentrations, and consists of subclinical hypothyroidism (SCH) and subclinical hyperthyroidism (SCHyper). For the proper diagnosis of SCH, it is most important to be able to correctly evaluate the serum TSH levels, which have numerous unique characteristics. We also need to be versed in TSH harmonization, which was recently launched world-wide. In this review, we will attempt to determine the best clinical approaches to the treatment of subclinical thyroid dysfunction based on recent guidelines published from several countries and novel findings of several recent large-scale clinical studies.

Prevalence of amiodarone-induced hypothyroidism; A systematic review and meta-analysis: Amiodarone-induced hypothyroidism epidemiology

Amiodarone is a common anti-arrhythmic agent mostly used to treat and prevent different kinds of arrhythmia with several considerable side effects, most commonly on the thyroid gland. We aimed to assess the frequency of hypothyroidism among chronic amiodarone users. PubMed/Medline, Web of Science, and Scopus databases were screened in the title and abstract sections with no time limitation. Relevant published records reported amiodarone-induced hypothyroidism (AIH) among patients with normal thyroid function at baseline were recruited with further analysis according to gender and study locations. We found 29 records on 14143 individuals. Total population age ranged from 18 to 92 years (males: 58.2% (8158 out of 13999)). The AIH prevalence was found to be 14% (95% confidence interval (CI): 12-17%). Further gender stratified showed an insignificant higher AIH frequency in females versus males (17%, 95% CI: 13-22% vs. 14%, 95% CI: 11-19% P= 0.304, respectively). Despite no significant difference in AIH prevalence according to different continents, African subjects had marginally lower AIH frequency compared to Asian (7%, 95% CI: 4-13% vs. 15%, 95% CI: 12-19%, P= 0.012) and South American persons (7%, 95% CI: 4-13% vs. 54%, 95% CI: 9-93%, P= 0.038). This review suggests the occurrence of AIH is quite considerable regardless of gender and area of residence, and several periodic thyroid assessment strategies should be developed for earlier recognition and therapeutic interventions in clinical settings.

Sarcoidosis: Various Presentations, Coexisting Diseases and Malignancies

Sarcoidosis is a rare, chronic inflammatory disease with a characteristic non-caseating granuloma formation. It affects women more than men. The lung is the most commonly affected organ, however, extrapulmonary involvement is also seen. Sarcoidosis can affect any organ or tissue and can also involve multiple organs simultaneously. As a disease, it shares clinical symptoms with a variety of autoimmune, non-autoimmune disorders and malignancies. Not only it mimics clinically, but it also coexists with these diseases, posing a significant diagnostic challenge. During this literature review, we obtained data from the previously published PubMed articles within the last five years and reviewed the possible etiological association and clinical coexistence between sarcoidosis and other diseases/malignancies. We aimed to determine the common clinical manifestations, various complex presentations of sarcoidosis and pathophysiological considerations for the association, and to emphasize the link with other diseases, particularly thyroid disorders/malignancies. Physicians should be aware of these associated diseases and should always make a clinical suspicion when confronting a sarcoidosis patient. Thus, a comprehensive diagnostic evaluation for these associated conditions ought to be done in sarcoidosis patients to avoid any delay in the curative treatment for these coexisting diseases and to prevent substandard outcomes.

Polypharmacy Is Associated With Amiodarone-Induced Hypothyroidism

Background: Amiodarone is rich in iodine, so in clinical practice amiodarone-induced hypothyroidism (AIH) is a major side effect. This drug is used in patients with arrhythmias, especially atrial fibrillation, the most common sustained arrhythmia. Polypharmacy, which can result in complex drug-drug interactions, occurs in more than 70% of the patients with atrial fibrillation. Therefore, polypharmacy may be involved in the expression of AIH. In this study, we investigated the association between polypharmacy and AIH. Methods: We conducted a retrospective study using data from January 2006 to May 2020 collected from a large, organized database of prescriptions constructed by the Japan Medical Information Research Institute, Inc. (Tokyo, Japan). To investigate the association between number of prescribed drugs with amiodarone and AIH, we divided patients into two groups: polypharmacy (≥ 5 prescribed drugs) and non-polypharmacy (< 5 prescribed drugs). We then performed a sequence symmetry analysis on the two groups: incident thyroxine after incident amiodarone and incident thyroxine before incident amiodarone. Finally, we conducted a case-control study on two further groups: those prescribed thyroxine after incident amiodarone (AIH group; n=555) and those not prescribed thyroxine after incident amiodarone (non-AIH group; n=6,192). Results: Sequence symmetry analysis revealed a significant association between amiodarone and thyroxine in both the polypharmacy and non-polypharmacy groups. The ranges for the adjusted sequence ratio in the two groups were 12.0-16.7 and 7.3-9.0, respectively. The case-control study showed that ≥5 prescribed drugs at the first prescription of amiodarone were found to significantly increase the odds of AIH (odds ratio: 1.48, 95% confidence interval: 1.18-1.84). Conclusion: Polypharmacy was suggested as an independent risk factor for AIH. Careful assessment of the appropriateness of prescription is warranted.

Role of Subclinical Iatrogenic Hyperthyroidism in the Setting of Heart Disease and Arrhythmic Burden

BACKGROUND

Subclinical hyperthyroidism is defined by a subnormal serum thyroidstimulating hormone (TSH) level with normal free thyroxine (FT4) and free triiodothyronine (FT3) levels. Its prevalence varies from 0.6% to 16% in the elderly and can increase to 20% in patients receiving thyroid hormone replacement therapy. Thyroid disease and/or replacement therapy are frequently associated with cardiovascular involvement.

CASES PRESENTATION

We report three clinical cases of patients with initial subclinical hyperthyroidism and cardiological manifestations, including supraventricular and ventricular extrasystoles, prolapse of the mitral valve with severe regurgitation, higher mean heart rate and deterioration of the arrhythmias on arrhythmogenic dysplasia substrate.

CONCLUSION

We discuss the role of appropriate and early correction of thyroid dysfunction in improving cardiological manifestations.

Effect of long-term amiodarone treatment on thyroid function in euthyroid Japanese patients: a 12-month retrospective analysis

Amiodarone is an effective antiarrhythmic drug. However, it is associated with changes in thyroid function in euthyroid patients due to its high iodine content and intrinsic drug effects. Studies have been conducted in iodine-deficient and iodine-sufficient countries; however, data from countries with excessive iodine intake are lacking. Thus, this study aimed to evaluate the effect of long-term amiodarone treatment on thyroid function in euthyroid Japanese patients. Japanese adults aged ≥18 years who were treated with amiodarone for at least 90 consecutive days were included in this retrospective chart review. Patients with abnormal thyroid function test results at baseline were excluded. Serial changes in thyroid function tests at baseline and at days 30, 90, 180, 270, and 360 were analyzed using a mixed-effects model for repeated measures. In total, 46 patients with a mean age of 63.7 years were evaluated. The mean TSH level significantly increased from 1.62 μIU/mL at baseline to 3.43, 2.75, 2.84, 2.78, and 2.65 μIU/mL at days 30, 90, 180, 270, and 360, respectively. The mean free T₄ level significantly increased from 1.3 ng/dL at baseline to 1.4, 1.5, 1.5, 1.5, and 1.5 ng/dL at days 30, 90, 180, 270, and 360, respectively. The mean free T₃ level significantly decreased from 2.8 pg/mL at baseline to 2.4, 2.3, 2.3, 2.4, and 2.4 pg/mL at days 30, 90, 180, 270, and 360, respectively. In conclusion, significant changes in thyroid function persisted not only in the acute phase but also in the chronic phase of long-term amiodarone treatment.

Amiodarone-induced thyrotoxicosis

Amiodarone-induced thyrotoxicosis (AIT) are not uncommon endocrinopathies. Clinicians are sometimes faced with difficult diagnostic and therapeutic situations. The disease pathophysiology is partially understood, explaining the lack of predictive factors for occurrence. Different international recommendations for their management have been published: the most recent in 2018 by the European Thyroid Association (ETA) (Ross et al., 2016; Bartalena et al., 2018). The purpose of this paper is to present the essential concepts for their management and to review the literature since 2018.

Influence of concomitant medication on plasma concentration of amiodarone in patients with atrial fibrillation - a pilot study

Background

Although amiodarone is a drug with many side effects, it is one of the most commonly used drugs in the treatment and prophylaxis of supraventricular and ventricular arrhythmias.

Aim

The purpose of this pilot study was to evaluate plasma concentrations of amiodarone in patients with atrial fibrillation (AF) and to identify possible drug-drug interactions between amiodarone and concomitant medications.

Method

A prospective observational study was conducted in 27 consecutive patients treated with amiodarone from May to July 2017 in a Clinical University Hospital. The patients included met our inclusion criteria. HPLC-UV was the device used to determine the plasma concentration of amiodarone.

Results

Only 51.8% of the patients had amiodarone plasma concentration within therapeutic interval (500–2500 ng/ml). The drugs associated to amiodarone in the therapeutic plan were diuretics, beta blockers, statins, antiplatelets, fluoroquinolones, non-steroidal anti-inflammatory drugs. We observed a statistically significant difference between the plasmatic concentrations of amiodarone in patients treated with furosemide vs. patients concomitantly treated with other drugs. Interactions between other mentioned drugs and amiodarone were not registered. We can report an underuse of amiodarone for more than 50% of the patients. Also, we found a significant interaction between furosemide and amiodarone, most likely through the interaction with MDR.

Conclusion

Furosemide may influence the pharmacokinetics of P-gp-interfering drugs. However, the relevance of these findings needs to be confirmed and further research is needed to characterize the interaction between amiodarone and furosemide.

Endocrine disruption as an adverse effect of non-endocrine targeting pharmaceuticals

Endocrine disruptors have gained widespread attention owing to their severe adverse health impacts. These produce enormous burden of disease and are associated with high economic cost especially in developed countries. Environmental pollutants causing endocrine disruption include pesticides, industrial wastes, packaging materials, food constituents, plastics, and cosmetic products. Likewise, pharmaceutical drugs have the endocrine disrupting potential through a wide array of mechanisms. Antipsychotic, antiepileptic, antihypertensive, antiviral, antidiabetic, and anticancer drugs are among the foremost non-hormonal endocrine disruptors. Several drugs affect thyroid hormone synthesis via interaction with iodine uptake to the release of T3 and T4 by thyrocytes. Prolonged use of some drugs increase susceptibility to diabetes mellitus either by direct destruction of β cells or enhanced insulin resistance. Other drugs may cause serious developmental defects in male or female reproductive system. Appropriate understanding of the mechanisms of endocrine disruption associated with non-hormonal drugs will guide future drug development and help us prevent and cure endocrine-related toxicity of pharmaceuticals. Therefore, this review focuses on endocrine disruption by pharmaceutical drugs as their side effect.