Preparation for thyroid surgery and radioactive iodine

Most patients with well controlled thyrotoxicosis require no special preparation for thyroid surgery or radio active iodine. However, people with uncontrolled thyrotoxicosis or who are intolerant of anti thyroid medications will require specific medical preparation to ensure surgery is safe and to ensure radioactive iodine is safe and effective.

Normal free thyroxine and liothyronine levels

Assuming these parameters are within or close to normal limits, the TSH result will not affect management in this situation. No special precautions are required prior to radio active iodine or surgery.

Surgery in the euthyroid patient

Continue anti thyroid drug until the day of surgery then stop. After total thyroidectomy for thyrotoxicosis it is usual to start all patients on levothyroxine 100mcg daily from day 1 post op, and recheck thyroid stimulating hormone at 6 weeks. 

Preparation for surgery in the thyrotoxic patient

Seek advice from an endocrinologist if thyroid results are still abnormal

Thyroid surgery can proceed safely in the presence of a suppressed TSH with normal thyroxine and liothyronine levels.

All patients with elevated thyroid hormone levels should be discussed with an endocrinologist to determine whether it is safe to proceed to surgery now.

Severe thyrotoxicosis

Patients who are clinically still very toxic or have fT4 levels above 28pmol/L or fT3 levels above 10pmol/L will require full preparation as below, though patients with lesser degrees of biochemical thyrotoxicosis should be assessed on an individual patient basis. 

Optimise anti thyroid drugs

In patients in whom anti thyroid drugs are not contra indicated, very high doses are useful to bring thyroid hormone levels down acutely prior to emergency surgery.

Doses of up to 80mg carbimazole a day can be used under specialist supervision and will produce a rapid fall in thyroid hormones within a week in many cases. 

Beta blockers

Give propranolol 40-80mg tds for at least 48 hours prior to emergency surgery, or diltiazem 60mg tds if beta blockade is contra indicated.


Prednisolone 20mg bd for up to a week will reduce T4 to T3 interconversion. This is useful prior to emergency thyroid surgery particularly in Graves' disease.

Lugol's iodine

Lugol's iodine 5 drops qds given in milk or orange juice for one week prior to surgery will block hormone production and release of preformed hormone.

Lugol's iodine is also known as Aqueous oral iodine solution. 5 drops contains approximately 32.5mg iodine.


If anti thyroid drugs are contra indicated, cholestyramine 3g tds orally, reduces enterohepatic circulation of thyroid hormones and so may reduce their circulating levels.


Lithium 250mg tds orally can also be used if standard anti thyroid drugs are contra indicated, as it has direct anti thyroid effects.

Lithium does typically take 1-2 weeks to be effective however, and monitoring of serum levels will be required due to its narrow therapeutic window.

Radio active iodine therapy

Stop carbimazole for 5 days prior to treatment and restart it 5 days after radio active iodine therapy. 

Stop propyl thiouracil for 10 days prior to treatment and restart it 5 days after radio active iodine therapy.

Patients who are well controlled on very low doses, may not need their anti thyroid drug restarted at all following treatment. 

Monitor thyroid function at 6 and 12 weeks post iodine, then 3 monthly for the first year, then annually thereafter to help guide when to reduce or stop anti thyroid drug therapy, and to seek eventual hypothyroidism.