Dysfunction of the thyroid gland during amiodarone therapy: a study of 297 cases.
OBJECTIVE
This study aims to explore and compare the efficacy of radioiodine treatment (RIT) in hyperthyroid and euthyroid patients who have been treated with amiodarone (AM) in the past or are currently undergoing AM treatment. Clinical observation of a group of patients with amiodarone-induced hypothyroidism during a 12-month follow-up period was used for comparison.


METHODS
This was a observational, two-centered study. Patients were assessed at baseline and at 2 months, 6 months, 8 months, and 12 months after RIT.


METHODS
Group A: At baseline (61 males [M] and 17 females [F], mean age 50±19 years), there were 78 euthyroid patients with cardiac arrhythmias, who were treated with AM and developed amiodarone-induced thyrotoxicosis, and currently require retreatment with AM. Group B: Hyperthyroid patients (92 M and 26 F, mean age 72±11.8 years) after AM therapy in the past. Group C: Hyperthyroid patients (66 M and 13 F, mean age 63.9±13.2 years) currently treated by AM. Group D: Hypothyroid patients (6 M and 16 F, mean age 61.4±10.4 years) after AM therapy. The patients from Groups A, B, and C were retreated with AM after ~3-6 weeks of RIT.


RESULTS
In Group A, after 12 months of RIT therapy, recurrent thyrotoxicosis was observed in six (7.7%) cases, and persistent hypothyroidism was diagnosed in 42 (53.8%) cases. In Group B, hyperthyroidism occurring during treatment with AM was found in 40 (33.9%) patients, and permanent hypothyroidism was observed in eleven (12.5%) cases. After annual follow-up in Group C, nine (11.4%) patients were diagnosed with hypothyroidism, while 27 (34.1%) patients were diagnosed with hyperthyroidism. In Group D, all patients had permanent hypothyroidism and when the concentration of serum thyroid-stimulating hormone was >10 µIU/mL, l-thyroxine was applied.


CONCLUSIONS
Our study showed that radioiodine administration is advisable in certain circumstances, even in euthyroid patients. It allows for continuation of further long-term AM treatment. Additionally, RIT allows for the reintroduction of AM therapy that was previously terminated. Hence, it can help control life-threatening tachyarrhythmias and decrease episodes of thyrotoxicosis.
Department of Endocrinology, Metabolism and Internal Medicine, Poznan, Poland; Department of Pharmacology, Poznan University of Medical Sciences, Poznan, Poland.
Agata
A
Czarnywojtek
Nuclear Medicine Department, Medical University of Warsaw, Warsaw, Poznan, Poland.
Maria Teresa
MT
Płazińska
Department of Health Prophylaxis, Laboratory of Medical Electrodiagnostics, Poznan, Poland.
Małgorzata
M
Zgorzalewicz-Stachowiak
Department of Endocrinology, Metabolism and Internal Medicine, Poznan, Poland.
Kosma
K
Woliński
Department of Endocrinology, Metabolism and Internal Medicine, Poznan, Poland.
Adam
A
Stangierski
Department of Computer Science and Statistics, Poznan, Poland.
Izabela
I
Miechowicz
Department of Endocrinology, Metabolism and Internal Medicine, Poznan, Poland.
Joanna
J
Waligórska-Stachura
Department of Endocrinology, Metabolism and Internal Medicine, Poznan, Poland.
Paweł
P
Gut
Nuclear Medicine Department, Medical University of Warsaw, Warsaw, Poznan, Poland.
Leszek
L
Królicki
Poznan University of Medical Sciences, Poznan, Poland.
Maja
M
Zioncheck
Department of Endocrinology, Metabolism and Internal Medicine, Poznan, Poland.
Marek
M
Ruchała
amiodarone; amiodarone-induced hypothyroidism; amiodarone-induced thyrotoxicosis; paroxysmal atrial fibrillation; radioactive iodine; radioiodine treatment; ventricular tachycardia