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.

Is the patient currently well / asymptomatic?

If the patient is asymptomatic and their thyrotoxicosis is biochemically well controlled, they will require no special precautions prior to surgery or radio active iodine.

Does the patient complain of a sore throat, mouth ulcers or fever?

These are the typical warning signs of possible agranulcytosis. All patients should receive written and verbal warnings to look out for these on starting anti thyroid drugs.

If a patient develops these symptoms, they must be told to stop their anti thyroid drug immediately, and have a full blood count tested urgently. They should only restart their therapy if their blood count is confirmed to be normal.

Neither surgery nor radio active iodine can be administered until the patient has fully recovered from their suspected sepsis, and their white cell count has normalised.

Does the patient still have symptoms suggestive of uncontrolled thyrotoxicosis?

If the patient is still obviously toxic, they will require beta blockade to control their symptoms during the acute period until they can safely undergo a definitive treatment. 

If the patient is very unwell, the possibility of storm should be considered, and if necessary appropriate treatment started e.g. with steroids and Lugol's iodine. 

How long has the patient had thyrotoxicosis and what is the cause?

It is useful to assess the cause and duration of thyrotoxicosis as this may affect alternative treatment choices e.g. newly diagnosed severe Graves disease demands urgent treatment, while treatment can be safely interupted in long standing subclinical thyrotoxicosis from a multinodular goitre.

Which anti thyroid drug and what dose is the patient currently taking?

Carbimazole is generally stopped for 5 days prior to radio active iodine, and restarted 5 days later if indicated. In patients well controlled, and taking very low doses e.g. 5mg carbimazole, it may be unnecessary to restart anti thyroid drugs following radio active iodine treatment.

Propyl thiouracil is generally stopped for 10 days prior to radio active iodine, and again restarted 5 days later if indicated. 

All anti thyroid drugs can be continued until the morning of surgery, then stopped.

What other drugs does the patient take at present?

Check all of the patient's medication history as well as their anti-thyroid drug history in case of other agents that may affect thyroid function or the efficacy of radio active iodine e.g. amiodarone.

Does the patient have any signs of active eye disease?

Patients with Graves' thyrotoxicosis should never undergo radio active iodine therapy if there is a suspicion of active eye disease.

All patients with a history of or current signs of eye disease should be seen by an ophthalmologist if available, prior to giving radio active iodine, to ensure that it is safe to proceed now, and to determine whether prophylactic steroids should be given.

Has the patient previously had an adverse reaction to anti thyroid drugs?

Agranulocytosis with an anti thyroid drug is an absolute contra indication to starting another anti thyroid agent.  Most other complications of anti thyroid drugs e.g. rash or mild abnormalities of liver function, can usually be monitored safetly and managed with symptomatic measures or dose reduction if required.

Emergency surgery or radio active iodine are generally reserved for patients in whom anti thyroid drgus are absolutely contra indicated, in which case special preparations will be required. Otherwise, proceed to definitive treatment only once the thyroid function has improved with a free thyroxine within or close to the normal range.