Thyroxine is a natural hormone that is made by the thyroid gland that lies in the neck in front of the voice box. This hormone is released into the blood and controls our metabolic rate. When we produce too little we can become tired, sluggish, gain weight, feel cold and puffy. When we produce too much we can become hyperactive, restless, lose weight, feel hot, have palpitations and develop a tremor. Normally the body very carefully controls how much thyroxine our thyroid gland produces to make sure everything stays nicely balanced.

Unfortunately if the thyroid gland is treated with radiotherapy, as happens in some radiotherapy for Hodgkin lymphoma or total body irradiation [TBI] in a bone marrow transplant, the gland can begin to fail. This doesn't happen suddenly but usually happens over several months to years. The symptoms of this can be very vague as it happens so gradually. Sometimes it just shows as a bit of weight gain and tiredness. Sometimes it is only detected by blood tests that your doctor will request every so often at your clinic visits.

The treatment for this problem is simple. You will need to start to take thyroxine tablets each day to replace the hormone that your thyroid gland can no longer make. Some times it can take a little while to find the right dose for you, as each person is different. Once you are settled on that dose, you will only need the occasional blood test to check everything is still all right.

The slowing of the thyroid gland doesn't do any long term harm but it does mean that you will need to go on taking thyroxine tablets for the rest of your life.