Effects of long-term amiodarone treatment on thyroid function.

Area of Science:

• Endocrinology
• Cardiology
• Pharmacology

Background:

• Coronary heart disease (CHD) patients often have altered thyroid function.
• Amiodarone is an effective antiarrhythmic drug but has known thyroid-related side effects.
• Euthyroid status in CHD patients requires careful monitoring during amiodarone therapy.

Purpose of the Study:

• To investigate the effects of amiodarone on thyroid hormone levels in euthyroid CHD patients.
• To analyze the patterns of thyroid-stimulating hormone (TSH) response to thyrotrophin-releasing hormone (TRH) during amiodarone treatment.
• To correlate changes in thyroid hormones and cholesterol levels.

Main Methods:

• Serum thyroid hormones (T4, T3, reverse T3, free T4, free T3 index) and cholesterol were measured in 18 euthyroid CHD patients.
• Patients received amiodarone (400 mg/day) for 16 months.
• Patients were grouped based on TSH response to TRH: normal (Group I) and subnormal (Group II).

Main Results:

• Group I patients showed increased total T4, free T4, reverse T3, and decreased total T3 and free T3 index.
• Group II patients had no T3 decrease and showed increased free T4 levels.
• Increased free T4 in Group II significantly correlated with decreased serum cholesterol (r = -0.767).
• No patient exhibited clinical signs of thyroid dysfunction.

Conclusions:

• Long-term amiodarone treatment frequently induces unpredictable hormonal patterns resembling hyperthyroidism in euthyroid CHD patients.
• These thyroid function alterations can occur without prior thyroid abnormalities.
• Monitoring thyroid function is crucial for patients on long-term amiodarone therapy, especially those with CHD.