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diffuse thyrotoxic goitre
Graves’ disease is the most common cause of overactive thyroid gland (hyperthyroidism). It is caused by an that acts like thyroid-stimulating (TSH) and causes the thyroid gland to produce excess thyroid hormones.
This antibody has been given a variety of names and abbreviations including: TSH-receptor antibodies (TRAbs or TSH-Rabs), thyroid stimulating (TSI), thyroid binding inhibiting immunoglobulins (TBII) and long acting thyroid stimulator (LATS).
Those most likely to have Graves' disease are women over 20 years of age. Affected people may have protruding eyes, weight loss, increased appetite and nervousness. Patients with the disease often have an increased heart rate and an enlarged thyroid gland (goitre).
In addition to thyroid function tests, thyroxine stimulating hormone (TSH), free thyroxine (FT4), free triiodothyroinine (FT3), additional tests that can help in the diagnosis include:
- Radioactive iodine uptake (increased).
A capsule or ‘cocktail’ containing a measured amount of radioactive iodine is swallowed; iodine is a critical component of thyroid hormones. The iodine accumulates in the thyroid; more accumulates when the gland is overactive, as occurs in Graves’ disease. After a specified amount of time, a probe similar to a Geiger counter is placed over the thyroid and the amount of radioactivity is compared to the amount that was given.
Often a radioactive substance called Technetium-99 pertechnetate is used as an alternative to radioactive iodine; it behaves like radioactive iodine but it is more convenient to use and delivers a lower radiation dose to the patient.
- TSH receptor antibodies (TRAbs).
In most patients with Graves’ disease the diagnosis can be made by the doctor following clinical examination together with the results of thyroid function tests and a thyroid scan. Because of this, the measurement of these antibodies is not always required.
The measurement of TRAbs is useful when the cause of an overactive thyroid gland is unclear or in pregnancy when hyperthyroidism is suspected. Early in a normal pregnancy some women have a brief period of mild hyperthyroidism due to the TSH-like activity of human chorionic gonoadotrophin (HCG) but this is often not recognised by the mother. This brief period of mild hyperthyroidism is not harmful to the mother or her unborn baby.
However, in pregnant patients with Graves’ disease the TRAbs antibodies may cross the placenta, over-stimulate the fetal thyroid gland, which may lead to miscarriage or poor growth of the baby. Since anti-thyroid drugs also cross the placenta, they treat both the maternal and fetal hyperthyroidism and it is essential to identify those pregnant women who have hyperthyroidism due to Graves’ disease.
A high concentration of TRAbs towards the end of pregnancy predicts neonatal thyrotoxicosis. TRAbs may remain present in patients who are euthyroid (normal thyroid) or even hypothyroid following treatment of Graves’ disease.
The measurement of TRAbs is therefore helpful: a) to identify Graves’ disease in pregnant women with hyperthyroidism, b) in pregnant women who have a past history of Graves’ disease and c) in patients following a course of drug treatment of Graves' disease to assess the risk of the disease returning.
- Anti-thyroid peroxidase antibody (present).
This autoantibody is found in most people with Graves’ disease, as well as in Hashimoto’s thyroiditis
Talking Results: what your Thyroid Function Test results can show
Treatment is designed to reduce the hormones produced by the thyroid gland and to reduce symptoms. Beta-blockers, such as propranolol, may relieve rapid heart rate, sweating, and anxiety caused by increased activity. Drugs that reduce thyroid hormone production are often given initially.
Often surgery to remove most or all of the thyroid gland is then used. Alternatively a large dose of radioactive iodine may be given to try to destroy most of the thyroid gland, eliminating the symptoms of hyperthyroidism. If the thyroid gland is totally destroyed, either by surgery or radioactive iodine, the patient will become hypothyroid and it will then be necessary for them to take thyroid hormone tablets from then on. Usually the protrusion of the eyes decrease as the hormone levels are lowered.
Last Review Date: March 16, 2017
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