Soru

An outpatient consultation is arranged for a $57$-year-old male due to a five-week history of significant weight loss, constant resting tremor, and profound heat intolerance. He has a known history of severe ischemic cardiomyopathy with a left ventricular ejection fraction of $25\%$, as well as recurrent sustained ventricular tachycardia for which an implantable cardioverter-defibrillator was placed two years ago. His medication regimen includes lisinopril, metoprolol succinate, spironolactone, and amiodarone. He has been taking amiodarone consistently for the past $20$ months.

Vital signs show a temperature of $37.1^\circ\text{C}$ ($98.8^\circ\text{F}$), blood pressure of $132/78 \text{ mmHg}$, and an irregular heart rate of $112/\text{min}$. Physical examination reveals a fine tremor of the outstretched hands and a hyperdynamic precordium. The thyroid gland is normal in size, non-tender, and without palpable nodules.

Laboratory studies reveal:
Thyroid-stimulating hormone (TSH): $<0.01 \mu\text{U/mL}$
Free thyroxine (T4): $4.6 \text{ ng/dL}$ (Reference: $0.8-1.8 \text{ ng/dL}$)
Total triiodothyronine (T3): $210 \text{ ng/dL}$ (Reference: $80-200 \text{ ng/dL}$)

A color flow Doppler ultrasonography of the anterior neck demonstrates a structurally normal thyroid gland with markedly reduced vascularity.

Which of the following is the most appropriate next step in the management of this patient's thyroid dysfunction?