INTRODUCTION
Graves’ disease is an autoimmune disorder affecting the thyroid gland. It is the most common cause of hyperthyroidism. Thyroid’s secretion of thyroid hormones [Triiodothyronine(T3) and Thyroxine(T4)] is regulated by thyroid stimulating hormone (TSH), which is released by the pituitary gland. These hormones regulate the body’s metabolic rate, heart function, brain development, bone maintenance and etc. In Graves’ disease, the immune system creates autoantibodies that mimic the function of TSH and stimulate production of more thyroid hormones. Consequently, this leads to hypersecretion of thyroid hormones. Excess thyroid hormones increase the body’s metabolic rate and speed up various body functions.
• Graves’ disease is characterized
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This may be due to a defect in suppressor T-lymphocyte function.
Three types of autoantibodies:
a) Thyroid-stimulating immunoglobulins
TSI are IgG antibodies that resemble the TSH and act as receptor agonist. They bind to and activate the thyrotropin (TSH) receptor. This results in hypertrophy (increase in size) and hyperplasia (increase in number) of the thyroid follicular cells and causing thyroid enlargement, visible as goitre. Stimulation of the TSH receptor also signals the thyroid gland to produce more thyroid hormones. However, the production of TSI is not regulated by the normal feedback mechanism. The continuous stimulation of thyroid gland by TSI causes hyperthyroidism.
b) TSH-binding inhibitory immunoglobulin
These autoantibodies prevent TSH from binding to its receptor. Some forms of TBII mimic the action of TSH and stimulate the secretion of thyroid hormones, whereas other forms inhibit thyroid cell function.
c) Thyroid growth-stimulating immunoglobulins
They are directed against TSH receptors and stimulate the growth of thyroid follicular epithelium.
2) The role of thyroid
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Various laboratory tests can then be carried out to confirm the diagnosis.
Thyroid-stimulating hormone (TSH) test is the most sensitive test to evaluate thyroid function and is usually the first test performed. TSH is a pituitary hormone that regulates the production of two hormones: thyroxine (T4) and triiodothyronine (T3).
T4 and T3 test is another blood test used to diagnose Grave’s disease. Generally, low levels of TSH and elevated levels of T4 and T3 indicate Graves’s disease. However, this may also occur in other cases of hyperthyroidism. Therefore, other tests can be performed to finalize the diagnosis.
Radioactive iodine uptake (RAIU) test and scan measure the amount of radioactive iodine taken up by the thyroid gland in a certain time period and also determine the distribution pattern of iodine in the thyroid gland. High uptake of iodine and distribution of iodine over the entire thyroid gland suggest Graves’ disease.
TREATMENT OF GRAVES’ DISEASE
1) Non-Pharmacological