When the thyroid gland produces an excess of hormones, many of the body’s functions are stimulated and metabolism speeds up.
An excess of thyroid hormones, known as hyperthyroidism, is one of the most common hormonal disorders. It’s most common in women between ages 20 and 50 and can run in families. About 3 out of 4 cases of the condition are due to Graves’ disease, an autoimmune disorder in which the immune system produces antibodies that attack the thyroid gland, resulting in overproduction of thyroid hormones.
Graves’ disease tends to run in families and is thought to have a genetic basis. In rare cases, hyperthyroidism may be associated with other autoimmune disorders, in particular the skin disorder vitiligo, and pernicious anaemia, a disorder of blood formation. In some cases thyroid nodules, often called “hot” nodules, secrete hormones, leading to hyperthyroidism. Inflammation of the thyroid gland may also temporarily produce the symptoms of hyperthyroidism.
What Are The Symptoms?
In most cases, symptoms of hyperthyroidism develop gradually over several weeks and may include:
- Weight loss despite increased appetite and food consumption
- Rapid heartbeat, which is sometimes also irregular, felt as palpitations
- Tremor (persistent trembling) affecting the hands
- Warm, moist skin as a result of excessive sweating
- Intolerance to heat
- Anxiety and insomnia
- Frequent bowel movements
- Swelling in the neck caused by an enlarged thyroid gland (goitre)
- Muscle weakness
- In women, irregular menstruation.
People with hyperthyroidism caused by Graves’ disease may also have bulging eyes, a condition called exophthalmos.
How Is It Diagnosed?
If your doctor suspects you have hyperthyroidism, a blood test to check for
abnormally high levels of thyroid hormones and for antibodies that can attack the thyroid gland will be arranged. Your doctor will also feel around your neck for lumps caused by general enlargement of the gland. If swelling is detected in the area of the thyroid gland, you may have radionuclide scanning to check for a hot nodule.
What Is The Treatment?
- Symptoms of hyperthyroidism can initially be relieved by beta-blocker drugs, which reduce tremor and anxiety but do not affect thyroid hormone levels.
- There are three main treatments aimed at reducing the production of thyroid hormones.
- The most common is anti-thyroid drugs, such as carbimazole and propranolol, which are used when hyperthyroidism is due to Graves’ disease and work by suppressing production of thyroid hormones. These drugs need to be taken daily for 12-18 months, after which the thyroid gland often functions normally.
- Radioactive iodine may be the most effective treatment for thyroid nodules that secrete hormone, and is also commonly used to treat Graves’ disease. Treatment involves drinking a dose of radioactive iodine in solution or swallowing a radioactive iodine capsule. The iodine is absorbed and accumulates in the thyroid gland, destroying part of it.
- Rarely, if drug treatments are ineffective, surgical removal of part of the thyroid gland may become necessary.
What Is The Outlook?
Many people recover fully following treatment. However, hyperthyroidism may recur, particularly in people who have Graves’ disease. If the treatment involves surgery or radioaedve iodine, the remaining part of the thyroid may not be able to produce sufficient hormones, leading to hypothyroidism. It is therefore important for thyroid hormone levels to be monitored regularly after treatment so that hormone supplements can be given if needed. The autoimmune form of hyperthyroidism may “burn out”, leaving behind a hypothyroid state.