Surgery for Thyrotoxicosis

Fig.1: Total thyroidectomy specimen of Graves' disease affected thyroidSurgery to remove the thyroid can be used to treat thyrotoxicosis in the following circumstances:

  • Patient preference
  • Need for rapid control
  • Large goitre with compressive symptoms
  • Allergy to all antithyroid drugs or relapse
  • Severe thyroid eye disease
  • Uncontrolled disease in pregnancy
  • Suspected cancer of the thyroid

Surgical options in thyrotoxicosis

The surgery is very similar to that for simple goitre, with the operation of total thyroidectomy  now the standard option (Fig. 1). It is the only operation that rapidly controls the thyrotoxicosis, and definitely leads to a permanent cure.

Surgery is generally indicated where there is compression of the trachea from a large goitre, the patient has relapsed after drug treatment or is unable or unwilling to have radioactive iodine. Other reasons are listed above.

Total thyroidectomy is also favoured over radioactive iodine when eye disease is present, as 15% of patients can worsen their disease after radioactive iodine. Surgery also has the advantage of reducing anti-TSH receptor antibody levels better than RAI over the long term, potentially reducing their impact on the eye disease of Graves' disease.

Subtotal thyroidectomy (leaving some thyroid tissue behind at operation) as a surgical option has been superseded as it leads to unacceptable results in 30% of patients. Because it is impossible in the individual case to know exactly how much thyroid tissue to leave behind the recurrence rate of thyrotoxicosis is 8-25%, and approximately 30-50% develop hypothyroidism after subtotal thyroidectomy. In experienced hands there is no difference in complication rates when a total thyroidectomy is performed, and patients have certainty about their thyroid status.

While subtotal thyroidectomy is generally satisfactory in most cases, the only operation that eliminates the risk of recurrence is total thyroidectomy. Although this operation virtually eliminates this risk, it comes at the cost of needing life-long thyroid hormone replacement, so patients need to be aware that this is inevitable. Some patients are against taking thyroxine however, despite the risks of recurrence, in which case subtotal thyroidectomy should be performed, leaving approximately 4-8 mls of thyroid tissue behind.

Hypocalcaemia (low calcium) is very common after surgery for thyrotoxicosis, as it is a condition which tends to deplete calcium in the bones over the long term. Hungry bone syndrome is not uncommon, so that calcium should be monitored closely in the postoperative period. Any calcium drop tends to be temporary however, and returns to normal after a few weeks to months of replacement therapy.

Thyroid storm

Thyroid storm or thyrotoxic crisis is a rare, but potentially life-threatening condition due to a massive release of thyroid hormones in patients with thyrotoxicosis. It is triggered by definitive treatment with either surgery or RAI in an inadequately controlled patient, or by an episode of severe illness or physical stress in a toxic patient. It almost never occurs now as patients are properly controlled prior to any definitive treatment of thyrotoxicosis.

The clinical features are dominated by a high fever, but other symptoms can occur such as tachycardia, hypertension, neurological symptoms (agitation, confusion, leading to coma)  and gastrointestinal problems (vomiting & diarrhoea). Hypertension may be followed by congestive heart failure, leading to hypotension and shock. Because thyroid storm is almost invariably fatal if left untreated, rapid diagnosis and aggressive treatment are critical.

Once the diagnosis is suspected patients are best managed in an intensive care unit. Treatment is designed to:

  • reduce thyroid hormone secretion - eg: antithyroid drugs and iodine
  • provide supportive therapy - eg: external cooling, IV fluids, oxygen, steroids and beta-blockers
  • treat the underlying cause eg: antibiotics if infection, diabetic control, etc.

Long-term follow up after surgery for thyrotoxicosis

Patients who have been treated by total thyroidectomy and thyroid replacement need minimal follow up, with only yearly thyroid function tests. Patients treated by subtotal thyroidectomy however need closer review because of the risk of recurrent hyperthyroidism as well as hypothyroidism.

Changes after treatment

Having thyrotoxicosis makes you feel that you have lots of energy and drive, but it comes at the expense of the health of your heart and bones particularly. It is like over-revving the engine of a motor car; it may make you go faster for a while, but it wears out the engine faster too and you are more likely to crash!

When you are treated by any of the measures mentioned on these webpages, and your body's metabolism is brought back under control, you must expect some changes, some of which can be quite distressing for a time. These changes are more noticeable if you are having surgery for your thyrotoxicosis, as the effect is more abrupt, and thyroid function returns to normal much more quickly than with the other treatments. The changes are also more marked if you are still a little toxic at the time of your operation.

It is very common to feel tired and lethargic after the treatment, as you must get used to being "normal" again; a small amount of weight gain is also common, but usually no more than about 3 kg, and of course if you are prepared for it to happen, you can prevent the weight increase by raising your exercise levels and altering your diet to adjust to the new circumstances.

These symptoms can be very distressing at first, but gradually wear off with time as you adjust to the way your body should be functioning. Of course I will also check your thyroid function with a blood test, after surgery or other treatment, to make sure you have enough replacement tablets, or enough residual function in the remaining thyroid.