What is hyperthyroidism?

Hyperthyroidism, also known as thyrotoxicosis, or overactive thyroid, is a condition which occurs when there is too much thyroid hormone in the body. The condition is more common in women than men.

What is the role of the thyroid gland?

The thyroid gland is found in the neck. It produces hormones which are released into the bloodstream to control the body's growth and metabolism. These hormones are called thyroxine and triiodothyronine, and they affect processes such as heart rate and body temperature, and help to turn food into energy to keep the body going.

Normally, the levels of thyroxine and triiodothyronine in the blood are carefully controlled so that these processes happen at a stable rate. However, in hyperthyroidism, the thyroid gland produces an excess amount of thyroxine, or tri-iodo-thyronine, which speeds up the body's energy consumption functions. As a result, the metabolism is accelerated, which causes symptoms such as:

• hyperactivity,
• an increased appetite, and
• sudden weight loss, or gain.

Overt and subclinical hyperthyroidism

There are several causes of hyperthyroidism, although the most common is Graves' disease, in which the body's immune system targets the thyroid gland and causes it to produce too much thyroid hormone.

Upon being diagnosed, hyperthyroidism can be classed as being either:

• overt - which means that it causes symptoms, or
• subclinical - when the levels of thyroid hormone are still within normal limits.

If it is not successfully controlled, hyperthyroidism can cause several other health problems, such as heart dysrhythmia (irregular heart rhythms), and osteoporosis (weak and brittle bones).

If left untreated, hyperthyroidism can be fatal. However, the condition can be effectively treated using medicines to slow the production of hormones from the thyroid gland, as well as radiotherapy, and in some cases, surgery.