Triiodothyronine (T3) as compared to T4 :
T3 is the main active thyroid hormone. It is more potent (less plasma protein bound) and faster acting than T4. How­ever, short duration of action limits its use for the treatment of hypothyroidism (requires lifelong treatment).
T3 is indicated for the treatment of myxedema coma.
Is more plasma protein bound
Is shorter acting
Is less potent
Has delayed action