Serum interleukin-6 in amiodarone-induced thyrotoxicosis

Area of Science:

• Endocrinology
• Cardiology
• Immunology

Background:

• Amiodarone, a cardiac drug rich in iodine, can cause thyrotoxicosis (AIT).
• AIT pathogenesis involves excessive thyroid hormone synthesis or amiodarone-induced thyroiditis.
• Elevated serum interleukin-6 (IL-6) is associated with thyroid inflammatory processes.

Purpose of the Study:

• To investigate the significance of serum IL-6 levels in amiodarone-induced thyrotoxicosis (AIT).
• To differentiate between AIT subtypes based on IL-6 levels and thyroidal radioiodine uptake (RAIU).

Main Methods:

• Cross-sectional study evaluating serum IL-6 and RAIU in 27 AIT patients (with and without prior thyroid disease), euthyroid amiodarone patients, hypothyroid amiodarone patients, spontaneous hyperthyroidism patients, nontoxic goiter patients, and healthy controls.
• Serum IL-6 levels were measured and compared across all groups.
• 24-h thyroidal radioiodine uptake (RAIU) was assessed in AIT patients.

Main Results:

• AIT patients without apparent thyroid abnormalities (AIT-) exhibited markedly higher serum IL-6 levels compared to all other groups.
• AIT patients with underlying thyroid disease (AIT+) showed IL-6 levels not significantly different from spontaneous hyperthyroidism.
• AIT- patients demonstrated low RAIU, while AIT+ patients had normal to high RAIU despite excess iodine.

Conclusions:

• Markedly elevated serum IL-6 and low RAIU in AIT- patients suggest amiodarone-induced thyroiditis as the cause of thyrotoxicosis.
• Treatment of two AIT- patients with prednisone led to significant reductions in IL-6 and thyroid hormone levels, normalizing them.
• Serum IL-6 levels and RAIU can help differentiate AIT etiologies and guide treatment.