Butterfly Thyroid Cancer Trust: Suppressive Thyroxine Treatment

If your career as a patient with thyroid cancer is longer than a few months, the chance is that you will have heard the phrase "suppressive thyroxine treatment" or "TSH suppression", most likely from your doctors.

Or you may have read about it. More to the point, the chance is you are on this treatment. So, who is being "suppressed" and why? The explanation you may have heard goes something like this:

TSH (thyroid stimulating hormone) is a chemical that comes from the pituitary gland. TSH stimulates thyroid tissue to grow.

The pituitary stops making TSH if there is an excess of thyroxine circulating in the blood.

So you are being treated with a dose of thyroxine which is enough to "suppress" the production of TSH and hopefully stop any thyroid cancer cells in your body growing.

Confused?

OK try this one: imagine a peaceful fishing village (the thyroid). The villagers (thyroid cells) send their catch (thyroxine) to the market (the rest of the body).

The fish merchant (pituitary gland) sends messages (TSH) to the villagers telling them to send more or less fish (thyroxine) depending on the demand.

Now, a gang of rogue criminals (cancer) within the village start to misbehave.

The police (doctors) come in to remove the troublemakers but they are a bit heavy-handed and destroy the whole village (thyroidectomy and radioiodine ablation).

If there are any rogue criminals still at large (thyroid cancer cells), they are still loyal to the fish merchant (pituitary) and are taking orders from him.

So the police (doctors) flood the market with fish (thyroxine) so that the merchant stops sending messages (TSH) to the criminals (thyroid cancer) who then calm down and cease to cause trouble.

To suppress the TSH, larger than average doses of thyroxine are required, which is why people with a history of thyroid cancer are often on more thyroxine than other patients.

The evidence that this is helpful comes from studies of thousands of patients with thyroid cancer.

The chance of the thyroid cancer coming back was found to be reduced by about 30% in patients who received suppressive thyroxine treatment compared with those who were on smaller doses of thyroxine.

This, however, appears to apply largely to people with thyroid cancer who are at high risk of having recurrences.

So many centres "relax" TSH suppression after a few years when it becomes clear that a particular patient is very unlikely to experience further problems with their cancer coming back.

It is unusual for suppressive thyroxine therapy to cause any symptoms and it is generally regarded as safe.

It is important that any changes to your thyroxine dose are made only by your Thyroid Cancer specialist and not your GP.

Dr P Perros FRCP
Consultant Endocrinologist
Freeman Hospital
Newcastle upon Tyne

Medical Advisor 'Butterfly Thyroid Cancer Trust'