Effect of high-dose intravenous glucocorticoid therapy on serum thyroid hormone concentrations in type 2 amiodarone-induced thyrotoxicosis: an exploratory 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.

The Utility of Intravenous Methylprednisolone as an Adjunct Treatment for Drug-Resistant Amiodarone-Induced Thyrotoxicosis

BACKGROUND

Amiodarone-induced thyrotoxicosis (AIT) may pose treatment challenges. We present a series of patients in which we achieved the normalisation of free T3 (FT3) using intravenous methylprednisolone (ivMP) in AIT refractory to thiamazole and oral prednisone. Namely, in three males (aged 56, 50 and 64, all with a history of AF and/or a low ejection fraction), an addition of ivMP resulted in the normalisation of FT3, which allowed successful thyroidectomy. In another case of a 65-year-old man, we initially succeeded in the normalisation of FT3 using ivMP from FT4 > 7.77 ng/dL (0.93-1.7) to 2.41 ng/dL and in that of FT3 from 14.95 pg/mL (2-4.4) to 2.05 pg/mL), but four weeks after stopping ivMP, despite the continuation of thiamazole and prednisone, there was rebound thyrotoxicosis: FT4 > 7.77 ng/dL and FT3-5.46 pg/mL. Intravenous MP was restated leading to a decline in FT4 to 2.51 ng/dL and in FT3 to 1.92 pg/mL, thus allowing a successful thyroidectomy. Finally, in a 78-year-old man with AF, goitre, and AIT resistant to thiamazole, prednisone and lithium carbonate, we obtained a reduction in FT4 to 1.51 ng/dL and in FT3 to 3.17 pg/mL after seven pulses of ivMP. Oral prednisone was gradually reduced and successfully stopped about six months later. He remained on low-dose thiamazole (5 mg od).

CONCLUSIONS

Pulse ivMP in addition to oral steroids may be a useful adjunct therapy either for the preparation of a thyroidectomy or as a treatment modality in drug-resistant AIT. Though a total cure is possible, there is a danger of a rebound worsening of thyrotoxicosis after premature discontinuation of ivMP.

Mortality After Total Thyroidectomy for Amiodarone-Induced Thyrotoxicosis According to Left Ventricular Ejection Fraction

OBJECTIVE

To report cardiac outcomes after total thyroidectomy for amiodarone-induced thyrotoxicosis according to the baseline left ventricular ejection fraction in a tertiary referral center.

STUDY DESIGN

Retrospective, monocentric.

SETTING

The tertiary health care system.

METHODS

Patients who underwent total thyroidectomy for amiodarone-induced thyrotoxicosis between 2010 and 2020 with age >18 and available preoperative left ventricular ejection fraction were included in this study. Patients were dichotomized into: group 1 with left ventricular ejection fraction ≥40% (mildly reduced/normal ejection fraction), and group 2 with left ventricular ejection fraction <40% (reduced ejection fraction).

RESULTS

There were 34 patients in group 1 and 17 to group 2. The latter were younger (median 58.4 [Q1-Q3 48.0-64.9] vs. 69.8 years in group 1 [59.8-78.3], p = .0035) and they presented more cardiomyopathy (58.8 vs. 26.5%, p = .030). Overall, the median time until surgery referral was 3.1 [1.9-7.1] months and 47.1% underwent surgery after restoration of euthyroidism. Surgical complications accounted for 7.8%. In group 2, the median left ventricular ejection fraction was significantly improved after surgery (22.5 [20.0-25.0] vs. 29.0% [25.3-45.5], p = .0078). Five-year cardiac mortality was significantly higher in group 2 (p < .0001): 47.0% died of cardiac causes versus 2.9% in group 1. A baseline left ventricular ejection fraction <40% and a longer time until surgery referral were significantly associated with cardiac mortality (multivariable Cox regression analysis, p = .015 and .020, respectively).

CONCLUSION

These results reinforce the idea that surgery, if chosen, should be performed quickly in patients with left ventricular ejection fraction <40%.

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

CONTEXT

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

STUDY DESIGN

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Cardiovascular Involvement in Thyrotoxicosis Resulting in Heart Failure: The Risk Factors and Hemodynamic Implications

Thyrotoxicosis is a clinical syndrome with persistently elevated concentrations of free triiodothyronine, free thyroxine, or both, which correlates with an increased thyroid metabolic function. This article has discussed the direct effect of increased thyroid hormone on the heart, as the thyroid hormone physiologically exhibits a close harmony with hormones of the cardiovascular system. This action can lead to disturbances in hemodynamic stability, exacerbating the possibility of developing complications such as heart failure and life-threatening arrhythmias. This article has also explored the multifaceted pathogenesis of thyrotoxicosis and various pharmacological treatment options, including beta-blockers and anti-thyroid drugs. This article has reviewed numerous studies that have concluded that the main goal of therapy should always aim to normalize thyroid hormone levels based on the etiology of the thyrotoxicosis, although cardiovascular conditions are associated with a higher rate of mortality.

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.

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.

Duration of Exposure to Thyrotoxicosis Increases Mortality of Compromised AIT Patients: the Role of Early Thyroidectomy

CONTEXT

Patients with amiodarone-induced thyrotoxicosis (AIT) and severely reduced left ventricular ejection fraction (LVEF) have a high mortality rate that may be reduced by total thyroidectomy. Whether in this subset of patients thyroidectomy should be performed early during thyrotoxicosis or later after restoration of euthyroidism has not yet been settled.

OBJECTIVES

Mortality rates, including peritreatment mortality and 5-year cardiovascular mortality, and predictors of death, evaluated by Cox regression analysis.

METHODS

Retrospective cohort study of 64 consecutive patients with AIT selected for total thyroidectomy from 1997 to 2019. Four groups of patients were identified according to serum thyroid hormone concentrations and LVEF: Group 1 (thyrotoxic, LVEF <40%), Group 2 (thyrotoxic, LVEF ≥40%), Group 3 (euthyroid, LVEF < 40%), Group 4 (euthyroid, LVEF ≥40%).

RESULTS

Among patients with low LVEF (Groups 1 and 3), mortality was higher in patients undergoing thyroidectomy after restoration of euthyroidism (Group 3) than in those submitted to surgery when still thyrotoxic (Group 1): peritreatment mortality rates were 40% versus 0%, respectively (P = .048), whereas 5-year cardiovascular mortality rates were 53.3% versus 12.3%, respectively (P = .081). Exposure to thyrotoxicosis was longer in Group 3 than in Group 1 (112 days, interquartile range [IQR] 82.5-140, vs 76 days, IQR 24.8-88.5, P = .021). Survival did not differ in patients with LVEF ≥40% submitted to thyroidectomy irrespective of being thyrotoxic (Group 2) or euthyroid (Group 4): in this setting, peritreatment mortality rates were 6.3% versus 4% (P = .741) and 5-year cardiovascular mortality rates were 12.5% and 20% (P = .685), respectively. Age (hazard ratio [HR] 1.104, P = .029) and duration of exposure to thyrotoxicosis (HR 1.004, P = .039), but not presurgical serum thyroid hormone concentrations (P = .577 for free thyroxine, P = .217 for free triiodothyronine), were independent predictors of death.

CONCLUSIONS

A prolonged exposure to thyrotoxicosis resulted in increased mortality in patients with reduced LVEF, which may be reduced by early thyroidectomy.