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Definition of Goiter, diffuse toxic

Goiter, diffuse toxic: Graves disease, the most common cause of hyperthyroidism (overactivity of the thyroid gland), with generalized diffuse overactivity ("toxicity") of the entire thyroid gland which becomes enlarged into a goiter.

There are three clinical components to Graves disease:

  • Hyperthyroidism (the presence of too much thyroid hormone),
  • Ophthalmopathy specifically involving exophthalmos (protrusion of the eyeballs),
  • Dermopathy with skin lesions.

The ophthalmopathy can cause sensitivity to light and a feeling of "sand in the eyes." With further protrusion of the eyes, double vision and vision loss may occur. The ophthalmopathy tends to worsen with smoking. The dermopathy of Graves' disease is a rare, painless, reddish lumpy skin rash that is an autoimmune process. It is caused by thyroid-stimulating antibodies which bind to and activate the thyrotropin receptor on thyroid cells.

Graves' disease can run in families. The rate of concordance for Graves' disease is about 20% among monozygotic (identical) twins, and the rate is much lower among dizygotic (nonidentical) twins, indicating that genes make only a modest contribution to the susceptibility to Graves' disease. No single gene is known to cause the disease or to be necessary for its development. There are well-established associations with certain HLA types. Linkage analysis has identified gene loci on chromosomes 14q31, 20q11.2, and Xq21 that are associated with susceptibility to Graves' disease.

Factors that can trigger the onset of Graves' disease include stress, smoking, radiation to the neck, medications (such as interleukin-2 and interferon-alpha), and infectious organisms such as viruses.

The diagnosis of Graves' disease is made by a characteristic thyroid scan (showing diffusely increased uptake), the characteristic triad of ophthalmopathy, dermopathy, and hyperthyroidism, or blood testing for TSI (thyroid stimulating immunoglobulin) the level of which is abnormally high.

Current treatments for the hyperthyroidism of Graves' disease consist of antithyroid drugs, radioactive iodine, and surgery. There is regional variation in which of these measures tends to be used -- for example, radioactive iodine is favored in North America and antithyroid drugs nearly everywhere else. The surgery, subtotal thyroidectomy, is designed to remove the majority of the overactive thyroid gland.

The disease is named for Robert Graves, who in 1835 first identified the association of goiter, palpitations, and exophthalmos.

Source: MedTerms™ Medical Dictionary
http://www.medterms.com/script/main/art.asp?articlekey=3616
Last Editorial Review: 10/30/2013

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