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

[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.

[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.

Medical treatment of thyrotoxicosis

Medical treatment is the primary therapeutic option for thyrotoxicosis/hyperthyroidism. Two groups of causes of thyrotoxicosis (i.e. thyrotoxicosis with hyperthyroidism and thyrotoxicosis without hyperthyroidism) need to be considered for therapeutic reasons. Herein we provide an updated review on the role of conventional medical therapies (i.e. β-blockers, antithyroid drugs [ATDs], corticosteroids, inorganic iodide, perchlorate, cholecystographic agents, lithium, cholestyramine) in the main causes of thyrotoxicosis, starting from the rationale subtending their clinical application.

Thyroid Ultrasound: Diffuse and Nodular Disease

Thyroid ultrasound with gray-scale and color Doppler is the most helpful imaging modality to differentiate normal thyroid parenchyma from diffuse or nodular thyroid disease by evaluating glandular size, echogenicity, echotexture, margins, and vascularity. The various causes of diffuse thyroid disease often have overlapping sonographic imaging features. Thyroid nodules may be hyperplastic or neoplastic, with most due to benign hyperplastic changes in architecture and benign follicular adenomas; only a small percentage are malignant. A systematic approach to nodule morphology that includes evaluation of composition, echogenicity, margin, shape, and any echogenic foci can guide decision to biopsy or follow nodules.

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.