Glossary

This glossary explains the meaning of the most frequently used clinical and related terms connected with the diagnosis and treatment of thyroid disorders.

agranulocytosis: a rare blood disorder characterised by a severe reduction in the number of white blood cells in the circulating blood. This will leave the sufferer susceptible to a variety of bacterial infections causing symptoms such as sore throat, mouth ulcers and high fever.

antibodies: these are produced by the body’s immune system as a defence mechanism against ‘foreign’ protein contained, for example, in bacteria. Antibodies are not normally formed against proteins that are part of the body.

autoimmune disease: antibodies are inappropriately produced which are directed against parts of the body. For example, in most patients with hypothyroidism, antibodies are formed that participate in the destruction of the thyroid gland, whereas in Graves’ disease antibodies directed against the surface of the thyroid cell stimulate it to overproduce thyroid hormones.

carbimazole: the drug most commonly used in the UK in the treatment of hyperthyroidism. It acts by interfering with the excessive production of thyroid hormones.

de Quervain’s thyroiditis: a form of viral thyroiditis that can occur following a viral infection of the thyroid.

euthyroid: a term for normal thyroid function.

exophthalmos: prominence of the eyes most commonly found in patients with hyperthyroidism caused by Graves’ disease. The exophthalmos may affect one or both eyes, may be apparent before the overactive thyroid gland develops and may appear for the first time after successful treatment of the hyperthyroidism.

fine needle aspiration (FNA): a test that involves passing a small needle into the thyroid gland and sucking out (aspirating) a small sample of tissue for examination under the microscope. This technique often avoids the need for surgery in patients with certain types of goitre.

genes: part of a body cell that contains the biological information of characteristics that parents pass to their children during reproduction. They control the growth and development of cells.

goitre: an enlarged thyroid gland.

Graves’ disease: the name given to the most common form of hyperthyroidism. Patients often have exophthalmos, a goitre and sometimes raised red patches on the legs known as pretibial myxoedema.

Hashimoto’s thyroiditis: the name given to a particular kind of goitre caused by autoimmune disease. Although the thyroid gland is enlarged, there is often evidence of hypothyroidism.

hormones: chemical messengers that alter the activity of specific target cells. They are produced in specific glands or organs and transported to their site of action in the bloodstream.

hyperthyroidism: condition resulting from an overactive thyroid gland.

hypothyroidism: condition resulting from an underactive thyroid gland.

myxoedema: this means the same as hypothyroidism, but is often used to describe patients in whom the thyroid underactivity is severe and of long standing.

postpartum thyroiditis: a transient disturbance in the balance of the thyroid gland which can occur in the first year after childbirth. There are usually no symptoms, but there may be symptoms of hyperthyroidism or hypothyroidism. Treatment is not usually necessary.

propranolol (Inderal): a drug belonging to the group known as beta blockers which alleviate some of the symptoms, for example tremor in patients with an overactive thyroid gland. Other members of the group include nadolol (Corgard) and sotalol (Sotacor).

proptosis: another word for exophthalmos.

propylthiouracil: this drug has a similar action to carbimazole. It is used if patients develop side effects to carbimazole and is prescribed to patients who are breast-feeding when hyperthyroid.

radioactive iodine (iodine-131): an isotope of iodine which is used in the investigation and treatment of hyperthyroidism.

tetany: this results from a low level of calcium in the blood with tingling in the hands, feet and around the mouth, and painful spasm of the muscles of the hands and feet.

thyroglobulin: a protein secreted by the thyroid gland. Its measurement is an important part of the follow-up of patients who have been treated for thyroid cancer. It is known as a ‘tumour marker’ because its presence in certain situations may indicate that the cancer has returned to other parts of the body.

thyrotoxicosis: another term for hyperthyroidism.

thyrotrophin (thyroid-stimulating hormone, TSH): a hormone secreted by the pituitary gland and responsible for controlling the output of thyroid hormones by the thyroid gland. In hypothyroidism caused by disease of the thyroid gland, TSH concentrations are elevated in the blood and in hyperthyroidism TSH concentrations are low.

thyroxine (T₄): a hormone secreted, along with triiodothyronine, by the thyroid gland. It has to be converted in the body to triiodothyronine before it is active. Thyroxine is available in tablet form for the treatment of hypothyroidism.

triiodothyronine (T₃): a hormone which, along with thyroxine, is secreted by the thyroid gland. It is responsible for controlling the metabolism of the body. Although available in tablet form, it is not usually prescribed for patients with hypothyroidism because it does not provide such good control as thyroxine.