Levothyroxine is the preferred therapy for hypothyroidism.
Liothyronine can cause abrupt increases in serum triiodothyronine (T3), which can
cause adverse effects, especially in older patients. A more stable, uniform level
of T3 is achieved by administering levothyroxine. Dessicated thyroid and liotrix
are combination agents that contain T3 and thus may have adverse effects similar
to those of liothyronine. Methimazole is used in the treatment of hyperthyroidism.