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Graves disease is a thyroid disorder characterized by goiter, exophthalmos, "orange-peel" skin, and hyperthyroidism. It is caused by an antibody-mediated auto-immune reaction, but the trigger for this reaction is still unknown. It is the most common cause of hyperthyroidism in the world, and the most common cause of general thyroid enlargement in developed countries.
In some parts of Europe the term Basedow’s disease or Graves-Basedow disease is preferred to Graves' disease.
Graves disease owes its name to the Irish doctor Robert James Graves, who described a case of goiter with exophthalmos in 1835. However, the German Karl Adolph von Basedow independently reported the same constellation of symptoms in 1840. As a result, on the European Continent the term Basedow's disease is more common than Graves' disease.
Several earlier reports exist but were not widely circulated. For example, cases of goiter with exophthalmos were published by the Italians Giuseppe Flajani and Antonio Giuseppe Testa, in 1802 and 1810 respectively. Prior to these, Caleb Hillier Parry, a notable provincial physician in England of the late 18th-century (and a friend of Edward Jenner), described a case in 1786. This case was not published until 1825, but still ten years ahead of Graves
However, fair credit for the first description of Graves disease goes to the 12th-century Persian physician Sayyid Ismail Al-Jurjani, who noted the association of goiter and exophthalmos in his Thesaurus of the Shah of Khwarazm, the major medical dictionary of its time.
Graves' disease may present clinically with one of the following characteristic signs:
The two signs that are truly diagnostic of Graves' disease (i.e. not seen in other hyperthyroid conditions) are exophthalmos and nonpitting edema. Goiter, which is caused by an enlarged thyroid gland and is diffusion goiter by nature, can be present with other forms of hyperthyroidism, although Graves' disease is the most common cause. A large goiter is visible to the naked eye, but a smaller goiter may not be clinically detectable, though X-rays or ultrasound can assist in detecting it.
Another sign of Graves' disease is hyperthyroidism, i.e. over-production of the thyroid hormones T3 and T4. Although, hypothyroidism has also been associated and may be the causating factor in some patients. Hyperthyroidism can be confirmed by measuring elevated blood levels of free (unbound) T3 and T4. Other useful laboratory measurements include thyroid-stimulating hormone (TSH, low in Graves' disease due to negative feedback from the elevated T3 and T4), and protein-bound iodine (elevated). Thyroid-stimulating antibodies may also be detected serologically.
Biopsy to obtain histiological testing is not normally required, but may be obtained if thyroidectomy is performed.
Thyroid-associated ophthalmopathy is one of the most typical symptom of Graves disease. It is known by a variety of terms, the commonest being Graves ophthalmopathy. Thyroid eye disease is an inflammatory condition which affects the orbital contents including the extraocular muscles and orbital fat. It is almost always associated with Graves disease but may rarely be seen in Hashimoto's thyroiditis, primary hypothyroidism, or thyroid cancer.
The ocular manifestations include soft tissue inflammation, eyelid retraction, proptosis, corneal exposure, and optic nerve compression. The signs and symptoms of the disease are characteristic. These include lid retraction, lid lag, and a delay in the downward excursion of the upper eyelid in down gaze that is specific to thyroid-associated ophthalmopathy.
Other Graves' disease symptoms
Some of the most typical symptoms of Graves' Disease are the following:
Incidence and epidemiology
The disease occurs most frequently in women (7:1 compared to men). It occurs most often in middle age (most commonly in the third to fifth decades of life), but is not uncommon in adolescents, during pregnancy, at the time of menopause and in people over age 50. There is a marked family preponderance, which has led to speculation that there may be a genetic component. To date, no clear genetic defect has been found that would point at a monogenic cause.
Graves' disease is an autoimmune disorder, in which the body produces antibodies to the receptor for thyroid-stimulating hormone (TSH). (Antibodies to thyroglobulin and to the thyroid hormones T3 and T4 may also be produced.)
These antibodies cause hyperthyroidism because they bind to the TSH receptor and chronically stimulate it. The TSH receptor is expressed on the follicular cells of the thyroid gland (the cells that produce thyroid hormone), and the result of chronic stimulation is an abnormally high production of T3 and T4. This in turn causes the clinical symptoms of hyperthyroidism, and the enlargement of the thyroid gland visible as goiter.
The infiltrative exophthalmos that is frequently encountered has been explained by postulating that the thyroid gland and the extraocular muscles share a common antigen which is recognized by the antibodies. Antibodies binding to the extraocular muscles would cause swelling behind the eyeball.
The "orange peel" skin has been explained by the infiltration of antibodies under the skin, causing an inflammatory reaction and subsequent fibrous plaques.
There are 3 types of autoantibodies to the TSH receptor currently recognized:
The trigger for auto-antibody production is not known. There appears to be a genetic predisposition for Graves' disease, suggesting that some people are more prone than others to develop TSH receptor activating antibodies due to a genetic cause. HLA DR (especially DR3) appears to play a significant role.
Since Graves' disease is an autoimmune disease which appears suddenly, often quite late in life, it is thought that a viral or bacterial infection may trigger antibodies which cross-react with the human TSH receptor (a phenomenon known as antigenic mimicry, also seen in some cases of type I diabetes).
One possible culprit is the bacterium Yersinia enterocolitica (a cousin of Yersinia pestis, the agent of bubonic plague). However, although there is indirect evidence for the structural similarity between the bacteria and the human thyrotropin receptor, direct causative evidence is limited. Yersinia seems not to be a major cause of this disease, although it may contribute to the development of thyroid autoimmunity arising for other reasons in genetically susceptible individuals. It has also been suggested that Y. enterocolitica infection is not the cause of auto-immune thyroid disease, but rather is only an associated condition; with both having a shared inherited susceptibility. More recently the role for Y. enterocolitica has been disputed.
The ocular manifestations of Graves disease are more common in smokers and tend to worsen (or develop for the first time) following radioiodine treatment of the thyroid condition. Thus, they are not caused by hyperthyroidism per se; this common misperception may result from the fact that hyperthyroidism from other causes may cause eyelid retraction or eyelid lag (so-called hyperthyroid stare) which can be confused with the general appearance of proptosis/exophthalmos, despite the fact that the globes do not actually protrude in other causes of hyperthyroidism. Also, both conditions (globe protrusion and hyperthyroid lid retraction) may exist at the same time in the hyperthyroid patient with Graves disease.
Treatment of Graves' disease includes antithyroid drugs which reduce the production of thyroid hormone, radioiodine (radioactive iodine I131), and thyroidectomy (surgical excision of the gland). As operating on a frankly hyperthyroid patient is dangerous, prior to thyroidectomy preoperative treatment with antithyroid drugs is given to render the patient "euthyroid" (i.e. normothyroid).
Treatment with antithyroid medications must be given for six months to two years, in order to be effective. Even then, upon cessation of the drugs, the hyperthyroid state may recur. Side effects of the antithyroid medications include a potentially fatal reduction in the level of white blood cells. The development and widespread adoption of radioiodine treatment has led to a progressive reduction in the use of surgical thyroidectomy for this problem. In general, RAI therapy is effective, less expensive, and avoids the small but definite risks of surgery.
Therapy with radioiodine is the most common treatment in the United States, whilst antithyroid drugs and/or thyroidectomy is used more often in Europe, Japan, and most of the rest of the world.
The main antithyroid drugs are carbimazole (UK), methimazole (US), and propylthiouracil (PTU). These drugs block the binding of iodine and coupling of iodotyrosines. The most dangerous side-effect is agranulocytosis (1/250, more in PTU); this is an idiosyncratic reaction which does not stop on cessation of drug. Others include granulocytopenia (dose dependent, which improves on cessation of the drug) and aplastic anemia. Patients on these medications should see a doctor if they develop sore throat or fever. The most common side effects are rash and peripheral neuritis. These drugs also cross the placenta and are secreted in breast milk. Lygole is used to block hormone synthesis before surgery
Radioiodine (radioactive iodine I-131) was developed in the early 1940s at the Mallinckrodt General Clinical Research Center. This modality is suitable for most patients, although some prefer to use it mainly for older patients. Indications for radioiodine are: failed medical therapy or surgery and where medical or surgical therapy are contraindicated.
Contraindications to RAI are pregnancy (absolute), ophthalmopathy (relative- it can aggravate thyroid eye disease), solitary nodules. Disadvantages of this treatment are a high incidence of hypothyroidism (up to 80%) requiring hormone supplementation. It acts slowly and has a relapse rate that depends on the dose administered.
This modality is suitable for young patients and pregnant patients. Indications are: a large goiter (especially when compressing the trachea), suspicious nodules or suspected cancer (to pathologically examine the thyroid) and patients with ophthalmopathy.
Both bilateral subtotal thyroidectomy and the Hartley-Dunhill procedure (hemithyroidectomy on 1 side and partial lobectomy on other side) are possible.
Advantages are: immediate cure and potential removal of carcinoma. Its risks are injury of the recurrent laryngeal nerve, hypoparathyroidism (due to removal of the parathyroid glands), hematoma (which can be life-threatening if it compresses the trachea) and scarring.
If left untreated, more serious complications could result, including birth defects in pregnancy, increased risk of a miscarriage, and in extreme cases, death. Graves-Basedow disease is often accompanied by an increase in heart rate, which may lead to further heart complications. If the eyes are proptotic (bulging) severely enough that the lids do not close completely at night, severe dryness will occur with a very high risk of a secondary corneal infection which could lead to blindness. Pressure on the optic nerve behind the globe can lead to visual field defects and vision loss as well.
B-blockers (such as propranolol) and translicvors are used to affect on sympathetic nervous system
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Graves_disease". A list of authors is available in Wikipedia.|