Which serum biochemical parameter is most important to measure to determine if symptoms on amiodarone are drug-related?

• A. T3 & T4 and TSH
• B. TSH only
• C. Creatinine
• D. ALT enzymes

Answer: (A)

Thyroid function is the most important parameter to check when symptoms may be related to amiodarone because this drug carries a large iodine load and can cause both hypo- and hyperthyroidism. Amiodarone can disrupt the thyroid axis in multiple ways, so you need to assess the whole picture of thyroid status. Measuring TSH provides a sensitive signal of thyroid dysfunction, but to determine the direction and magnitude of the problem you also need thyroid hormones, typically free T4 (and, if needed, T3). This combination helps distinguish whether symptoms stem from hypothyroidism or hyperthyroidism, guiding appropriate management such as adjusting amiodarone or addressing thyroid disease. While ALT enzymes and creatinine are useful for monitoring potential liver or kidney toxicity, they are less informative about the specific cause of symptoms related to amiodarone and thyroid effects.