Unfortunately about 40 per cent of cases relapse when the drugs are stopped, and then operation is usually considered.
Operation with removal of most of the thyroid gland is used when medical treatment fails or where the gland is nodular or grossly enlarged.
In people over 40 radioactive iodine is the treatment chosen. Iodine is a major constituent of thyroxin and when the radioactive isotope is given it is taken up by the thyroid gland and the radiation destroys the over-active tissue.
The aim of operation is to remove about three-quarters of the gland and the remaining tissue is usually sufficient to maintain normality.
This is easily treated by giving patients thyroxin tablets which they have to take for the rest of their lives.
Occasionally the over-activity of the body and too rapid beating of the heart may lead to abnormalities of rhythm of the heart or even to heart failure.
The heart condition usually needs to be controlled before the thyroid gland can be adequately treated. In some people the onset of thyrotoxicosis seems to be precipitated by severe emotional shock.