Anatomy and Function
The thyroid gland is a 2 inch long butterfly-shaped endocrinologic organ located at the front of the neck, below the Adam's apple. It synthesizes and secretes thyroid hormones that affect basal metabolic rate, sympathetic nerve tone, and development. Therefore, thyroid hormone is associated with various body functions including heart rate, breathing, body weight, body temperature, body composition, appetite, emotion, sleep, sexual function, menstrual cycle, and more.
Thyrotoxicosis is a state of excessive production or release of thyroid hormones. The clinical symptoms and signs of thyrotoxicosis include weight loss, palpitations, fatigue, anxiety, sweating, heat intolerance, disturbed sleep, and tremor of the extremities. The prevalence of thyrotoxicosis is about 2%, and 70–90% of cases are caused by Graves’ disease, although the rates and causes vary between geographical regions.
Graves’ disease is an autoimmune disease. A human body acquires immunity by producing antibodies. Generally, antibodies act against foreign materials (like bacteria or viruses). But some antibodies act against the human body itself. We call this kind of antibodies 'autoantibodies'. Abnormally increased auto-antibodies which act against the thyroid gland stimulate the production and release of thyroid hormones and result in the symptoms and signs of thyrotoxicosis. These antibodies also result in gradual protrusion of the eyes, called Graves' ophthalmopathy.
There are 3 options for treating patients with this disease: antithyroid drugs (ATDs), radioactive iodine ablation, and surgery. The choice of treatment for Graves’s disease differs between geographical regions. Radioactive iodine therapy is frequently used as the first-line therapy in North America. In Europe and Asia, ATDs such as methimazole, propylthiouracil are preferred as the primary treatment. Recently, concerns over complications from radioactive iodine therapy or surgery resulted in higher rates of drug treatment for this disease in North America.
A drawback of ATD therapy is the high rate of relapse of hyperthyroidism after the drug has been discontinued. Relapse is more frequent in the first year than in subsequent years, particularly in the first 6 months after stopping the medication. The risk of recurrence varies greatly between patients but is estimated to be 50–55%.
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