The only other 'cure' for hyperthyroidism 

Requires anesthesia which can be very risky in a cat with hyperthyroidism due to potential heart disease, low body condition scores, hypertension, etc. 

Requires a skilled surgeon due to the location of the parathyroid glands. These 4 little glands (located within or near the thyroid gland) are responsible for calcium regulation. If these glands are damaged/removed during surgery this can result in a life-threatening decrease in blood calcium levels.

Multiple surgeries can sometimes be needed if both lobes of the gland are enlarged or if other thyroid tissue is involved. 

Small remnants of thyroid tissue are normally found spread throughout the neck and chest making them impossbile to pinpoint and remove. 

After unsuccessful surgical therapy, many cats are finally treated with radioiodine (I-131) and are cured.