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

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.

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

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.

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).

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.