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Grave’s Disease

Dr Healthism
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  • 22 Feb, 2019 10:58 am
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Graves’ disease, also known as toxic diffuse goiter, is an autoimmune disease that affects the thyroid. It frequently results in and is the most common cause of hyperthyroidism. It also often results in an enlarged thyroid. Signs and symptoms of hyperthyroidism may include irritability, muscle weakness, sleeping problems, a fast heartbeat, poor tolerance of heat, diarrhea, and unintentional weight loss. Other symptoms may include thickening of the skin on the shins, known as pretibial myxedema, and eye bulging, a condition caused by Graves’ ophthalmopathy. About 25 to 80% of people with the condition develop eye problems.

The exact cause is unclear; however, it is believed to involve a combination of genetic and environmental factors. A person is more likely to be affected if they have a family member with the disease. If one twin is affected, a 30% chance exists that the other twin will also have the disease. The onset of disease may be triggered by stress, infection, or giving birth. Those with other autoimmune diseases such as type 1 diabetes and rheumatoid arthritis are more likely to be affected. Smoking increases the risk of disease and may worsen eye problems. The disorder results from an antibody, called thyroid-stimulating immunoglobulin (TSI), that has a similar effect to thyroid stimulating hormone (TSH). These TSI antibodies cause the thyroid gland to produce excess thyroid hormone. The diagnosis may be suspected based on symptoms and confirmed with blood tests and radioiodine uptake. Typically, blood tests show a raised T3 and T4, low TSH, increased radioiodine uptake in all areas of the thyroid, and TSI antibodies.

Signs and Symptoms
The signs and symptoms of Graves’ disease virtually all result from the direct and indirect effects of hyperthyroidism, with main exceptions being Graves’ ophthalmopathy, goiter, and pretibial myxedema (which are caused by the autoimmune processes of the disease). Symptoms of the resultant hyperthyroidism are mainly insomnia, hand tremor, hyperactivity, hair loss, excessive sweating, itching, heat intolerance, weight loss despite increased appetite, diarrhea, frequent defecation, palpitations, periodic partial muscle weakness or paralysis in those especially of Asian descent, and skin warmth and moistness. Further signs that may be seen on physical examination are most commonly a diffusely enlarged (usually symmetric), nontender thyroid, lid lag, excessive lacrimation due to Graves’ ophthalmopathy, arrhythmias of the heart, such as sinus tachycardia, atrial fibrillation, and premature ventricular contractions, and hypertension. People with hyperthyroidism may experience behavioral and personality changes, including: psychosis, mania, anxiety, agitation, and depression.

Cause
The exact cause is unclear; however, it is believed to involve a combination of genetic and environmental factors. While a theoretical mechanism occurs by which stress could cause an aggravation of the autoimmune response that leads to Graves’ disease, more robust clinical data are needed for a firm conclusion.

Genetics
A genetic predisposition for Graves’ disease is seen, with some people more prone to develop TSH receptor activating antibodies due to a genetic cause. Human leukocyte antigen DR (especially DR3) appears to play a role. To date, no clear genetic defect has been found to point to a single-gene cause.

Genes believed to be involved include those for thyroglobulin, thyrotropin receptor, protein tyrosine phosphatase nonreceptor type 22, and cytotoxic T-lymphocyte–associated antigen 4, among others.

Infectious trigger
Since Graves’ disease is an autoimmune disease which appears suddenly, often later in life, a viral or bacterial infection may trigger antibodies which cross-react with the human TSH receptor, a phenomenon known as antigenic mimicry.

The bacterium Yersinia enterocolitica bears structural similarity with the human thyrotropin receptor and was hypothesized to contribute to the development of thyroid autoimmunity arising for other reasons in genetically susceptible individuals. In the 1990s, it was suggested that Y. enterocolitica may be an associated condition with both diseases having a shared inherited susceptibility. More recently, the role for Y. enterocolitica has been disputed.

Epstein-Barr virus (EBV) is another potential trigger.

Diagnosis
Graves’ disease may present clinically with one or more of these characteristic signs:

Rapid heartbeat (80%)
Diffuse palpable goiter with audible bruit (70%)
Tremor (40%)
Exophthalmos (protuberance of one or both eyes), periorbital edema (25%)
Fatigue (70%), weight loss (60%) with increased appetite in young people and poor appetite in the elderly, and other symptoms of hyperthyroidism/thyrotoxicosis
Heat intolerance (55%)
Tremulousness (55%)
Palpitations (50%)
Two signs are truly ‘diagnostic’ of Graves’ disease (i.e., not seen in other hyperthyroid conditions): exophthalmos and nonpitting edema (pretibial myxedema). Goiter is an enlarged thyroid gland and is of the diffuse type (i.e., spread throughout the gland). Diffuse goiter may be seen with other causes of hyperthyroidism, although Graves’ disease is the most common cause of diffuse goiter. A large goiter will be visible to the naked eye, but a small one (mild enlargement of the gland) may be detectable only by physical examination. Occasionally, goiter is not clinically detectable, but may be seen only with computed tomography or ultrasound examination of the thyroid.

Another sign of Graves’ disease is hyperthyroidism, i.e., overproduction of the thyroid hormones T3 and T4. Normal thyroid levels are also seen, and occasionally also hypothyroidism, which may assist in causing goiter (though it is not the cause of the Graves’ disease). Hyperthyroidism in Graves’ disease is confirmed, as with any other cause of hyperthyroidism, by measuring elevated blood levels of free (unbound) T3 and T4.

Other useful laboratory measurements in Graves’ disease include thyroid-stimulating hormone (TSH, usually undetectable in Graves’ disease due to negative feedback from the elevated T3 and T4), and protein-bound iodine (elevated). Serologically detected thyroid-stimulating antibodies, radioactive iodine (RAI) uptake, or thyroid ultrasound with Doppler all can independently confirm a diagnosis of Grave’s disease.

Biopsy to obtain histiological testing is not normally required, but may be obtained if thyroidectomy is performed.

The goiter in Graves’ disease is often not nodular, but thyroid nodules are also common. Differentiating common forms of hyperthyroidism such as Graves’ disease, single thyroid adenoma, and toxic multinodular goiter is important to determine proper treatment. The differentiation among these entities has advanced, as imaging and biochemical tests have improved. Measuring TSH-receptor antibodies with the h-TBII assay has been proven efficient and was the most practical approach found in one study.

Management
Treatment of Graves’ disease includes antithyroid drugs which reduce the production of thyroid hormone; radioiodine (radioactive iodine I-131); 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). Each of these treatments has advantages and disadvantages. No one treatment approach is considered the best for everyone.

Treatment with antithyroid medications must be given for six months to two years to be effective. Even then, upon cessation of the drugs, the hyperthyroid state may recur. The risk of recurrence is about 40–50%, and lifelong treatment with antithyroid drugs carries some side effects such as agranulocytosis and liver disease. Side effects of the antithyroid medications include a potentially fatal reduction in the level of white blood cells. Therapy with radioiodine is the most common treatment in the United States, while antithyroid drugs and/or thyroidectomy are used more often in Europe, Japan, and most of the rest of the world.

β-Blockers (such as propranolol) may be used to inhibit the sympathetic nervous system symptoms of tachycardia and nausea until such time as antithyroid treatments start to take effect. Pure β-blockers do not inhibit lid-retraction in the eyes, which is mediated by alpha adrenergic receptors.

Prognosis
If left untreated, more serious complications could result, including birth defects in pregnancy, increased risk of a miscarriage, bone mineral loss and, in extreme cases, death. Graves’ disease is often accompanied by an increase in heart rate, which may lead to further heart complications, including loss of the normal heart rhythm (atrial fibrillation), which may lead to stroke. If the eyes are proptotic (bulging) enough that the lids do not close completely at night, dryness will occur – with the 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. Prolonged untreated hyperthyroidism can lead to bone loss, which may resolve when treated.

Epidemiology
Graves’ disease occurs in about 0.5% of people. It occurs about 7.5 times more often in women than in men. Often it starts between the ages of 40 and 60. It is the most common cause of hyperthyroidism in the United States (about 50 to 80% of cases).

History
Graves’ disease owes its name to the Irish doctor Robert James Graves, who described a case of goiter with exophthalmos in 1835. Medical eponyms are often styled nonpossessively; thus Graves’ disease and Graves disease are variant stylings of the same term.

The German Karl Adolph von Basedow independently reported the same constellation of symptoms in 1840. As a result, on the European Continent, the terms Basedow’s syndrome, Basedow’s disease, or Morbus Basedow are more common than Graves’ disease.

Graves’ disease has also been called exophthalmic goiter.

Less commonly, it has been known as Parry’s disease, Begbie’s disease, Flajani’s disease, Flajani–Basedow syndrome, and Marsh’s disease. These names for the disease were derived from Caleb Hillier Parry, James Begbie, Giuseppe Flajani, and Henry Marsh. Early reports, not widely circulated, of 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 Miller-Gallus), described a case in 1786. This case was not published until 1825, which was 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.

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