Definition Hyperthyroidism is a disorder that is caused by elevated levels of thyroid hormone.
What is going on in the body? The thyroid gland is a small endocrine gland located at the base of the neck. It produces thyroid hormone, which controls the processes which allow the body to transform food into energy and to rebuild cells. In a person with hyperthyroidism, the body produces too much thyroid hormone.
What are the signs and symptoms of the condition? The symptoms of hyperthyroidism are caused by high levels of thyroid hormone. Symptoms can include:
nervousness
palpitations
tremors
sweating
increased activity in the intestinal tract
changes in menstruation
weight loss
Some people find it more difficult to tolerate heat. Some feel anxious or restless. Changes in fingernails and hair may be noticed. The heart may beat irregularly, or even become enlarged.
What are the causes and risks of the condition? There are several causes of hyperthyroidism. In some people, the immune system produces antibodies that activate and stimulate the thyroid gland. This causes the gland to produce excessive amounts of hormones. A common example of this is Graves' disease. Other forms of hyperthyroidism may be caused by thyroiditis, or inflammation of the thyroid gland. Certain benign or malignant tumours can also produce too much thyroid hormone. Some forms of goitres can enlarge and produce excess thyroid hormone.
What can be done to prevent the condition? There is no known way to prevent hyperthyroidism.
How is the condition diagnosed? The diagnosis of hyperthyroidism is based on both a physical examination and laboratory work. The physical examination will look for the signs and symptoms of hyperthyroidism. Laboratory tests of the blood show higher levels of thyroid hormone and lower levels of thyroid-stimulating hormone (TSH). In some cases, the tests can detect antithyroid antibodies. A nuclear medication test called a thyroid uptake scan, measures how well the thyroid is functioning. This can help diagnose the specific cause of hyperthyroidism.
What are the long-term effects of the condition? Long-term effects can include metabolic problems and changes in skin, hair, and nails. Hyperthyroidism can also lead to osteoporosis, or thinning of the bones. People with Graves' disease may have changes in the eyes that persist despite treatment.
What are the risks to others? Hyperthyroidism does not involve any risk to others.
What are the treatments for the condition? The main treatment of hyperthyroidism is to reduce the production of thyroid hormone. This can be done with drugs, such as:
propylthiouracil
carbimazole (neo-mercazole)
potassium iodide
Medications called beta-blockers, such as atenolol, propanolol, or metoprolol, can also used to block the effects of thyroid on tissues.
Some people are treated by altering or destroying the thyroid gland using radioactive iodine. Radioactive iodine is taken up by the thyroid gland and destroys the excessive thyroid tissue. This treatment is commonly used in Graves' disease. It is not helpful in people with thyroiditis. Surgery is not usually done, except in the case of a tumour that secretes thyroid hormone.
What are the side effects of the treatments? The side effects of treatment depend on the medications used. When radioactive iodine is used to destroy the thyroid gland, people will usually need thyroid hormone replacement therapy for the rest of their lives. Pregnant women should not receive radioactive iodine.
What happens after treatment for the condition? After a person is treated for hyperthyroidism, the levels of thyroid hormone will continue to be checked. Medications are adjusted to maintain normal levels. Blood tests are used to confirm the level of thyroid hormone production.
How is the condition monitored? The condition is monitored by regular physical examinations and blood tests.
Author: Bill Harrison, MD Reviewer: HealthAnswers Australia Medical Review Panel Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia Last Updated: 1/10/2001 Contributors Potential conflict of interest information for reviewers available on request
