A 15-year-old male adolescent with type 1 diabetes presents with hypothyroidism. His TSH is high at 8.4 mIU/L, and his free T4 is 0.25 times lower than the lower limit of normal. He has been experiencing constipation, weight gain, and fatigue. Which would be considered the best initial treatment for him?
a. Liothyronine.
b. Desiccated thyroid.
c. Levothyroxine.
d. Lugol solution.