What is the most appropriate next step in management?

A 64-year-old man presented with palpitations, fatigue and malaise. Two months previously, he had sustained an acute myocardial infarction complicated by ventricular tachycardia and cardiac arrest, and had been discharged taking amiodarone 200 mg daily.

On examination, he appeared well, his pulse was 90 beats per minute and regular, and he had mild tremor of his hands but no other abnormal signs.

Investigations:

serum thyroid-stimulating hormone6.2 mU/L (0.4C5.0)

serum free T418.2 pmol/L (10.0C22.0)

serum free T34.8 pmol/L (3.0C7.0)

What is the most appropriate next step in management?
A . discontinue amiodarone
B . isotope scan of thyroid
C . repeat thyroid function tests in 2 months
D . repeat thyroid function tests in 12 months
E . start levothyroxine