GRAVES' DISEASE (hyperthyroidism, thyrotoxicosis) IN CHILDHOOD

Cause.

Overactivity of the thyroid gland is rare in childhood but increases in frequency into young adult life, affecting girls more than boys. It is nearly always due to Graves' disease, now recognised to be an "autoimmune" condition, in which antibodies (proteins circulating in the blood whose usual function is to protect against infection) react with the body's own organs causing damage or, in this condition, stimulation. The cause is not known but it is clear that some people are genetically more susceptible than others and it is probable that a virus infection may act as the final trigger. Similar antibodies may cause underactivity of the thyroid (sometimes called Hashimoto's disease) and both conditions often occur in the same families.

Symptoms.

The overstimulated thyroid gland produces too much thyroid hormone (thyroxine) which in turn has the effect of accelerating the chemical processes in most of the cells of the body. The affected child becomes progressively more anxious, nervous and restless with disturbed sleep, deteriorating school performance (especially the handwriting), racing pulse even in sleep, increased appetite, weight loss, excessive sweating, tremor and diarrhoea. Because the onset of the symptoms is gradual and the pattern is variable, psychological disturbance is often suspected before the true problem is identified. The thyroid gland in the front of the neck becomes enlarged, but this may not be at all obvious. In only a minority of children do the eyes become prominent (exopthalmos, proptosis) but this can be a major feature of the disease.

Diagnosis.

Once suspected, hyperthyroidism is easily confirmed by checking the thyroxine and thyroid stimulating hormone levels in the blood.

Treatment.

There are three methods of treatment available:

1. Drugs.

Children are started on either carbimazle or prpylthiouracil. These are antithyroid drugs. Both are generally well tolerated but can produce side effects in about 5% of children; these are usually just skin rashes but severe effects on blood cells have very rarely occurred. For this reason if any acute infection occurs in a child on treatment, the blood count should be checked.

2. Surgery.

The thyroid gland can be subtotally removed. This is a major operation which inevitably leaves a visible scar and can rarely cause damage to the nerves controlling the larynx or to the parathyroid glands which lie just behind the thyroid. Since it is not possible to judge exactly how much gland to remove there can be recurrence of thyroxicosis or thyroid underactivity can occur after surgery.

3. Radioiodine.

A radioactive isotope of iodine (131I) can be given by mouth in a watery solution which is then concentrated by the thyroid gland and gradually destroys the secreting cells. This form of treatment is simple and has an excellent safety record (after more than 40 year's use) but it does inevitably destroy the function of the gland so thyroid underactivity (hypothyroidism) develops and lifelong thyroxine replacement is needed.

Outlook.

For children we generally recommend a course of treatment with carbimazole to control the thyroid overactivity. If it is well tolerated drug treatment is usually continued for 18 months to two years because there is a reasonable chance (about 25%) that the disease may recover spontaneously within that time. If hyperthyroidism recurs when the treatment is stopped, drug treatment can be resumed for a further period. After this, either of the other treatments, surgery or radioiodine, will be considered.