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Too much thyroid hormone in blood leads to other problems

Hyperthryroidism is the term used when there is too much thyroid hormone in the blood. This condition makes many of the body’s functions speed up. Hyperthyroidism can be caused by thyroid nodules, thyroiditis or consuming too much iodine. Symptoms include nervousness, fatigue and rapid, irregular heartbeat. Women develop hyperthyroidism more often than men, and it is more common in people who are older than 60 years. Interestingly, older adults with hyperthyroidism may lose their appetites, but younger people with the condition may have increased appetites. Hyperthyroidism is treated with medications, radioiodine therapy or thyroid surgery.

Graves’ disease is the most common cause of hyperthyroidism in the United States. It was named after a British physician, Robert James Graves. Graves’ disease is an autoimmune disorder. According to the American Thyroid Association (ATA) (www.thyorid.org), the immune system makes an antibody called thyroid-stimulating immunoglobulin (TSI) that attaches to thyroid cells. TSI stimulates the thyroid to make too much thyroid hormone, but it sometimes blocks thyroid hormone production, leading to conflicting symptoms that may make correct diagnosis of hyperthyroidism more difficult. Symptoms of Graves’ disease include nervousness, fatigue, muscle weakness, heat intolerance and goiter or enlarged thyroid. Graves’ disease is characterized by a slight protrusion of the eyeballs, a condition called exopthalmus.

The condition usually occurs in people who are 40 years of age and younger. It is more common in women than in men. A person’s odds of developing Graves’ disease increases if he or she has other family members with the condition. It is also associated with type 1 diabetes and rheumatoid arthritis.

Physicians rely on physical examination and the patient’s medical history to diagnose Graves’ disease. Blood tests are also utilized. The thyroid-stimulating (TSH) test detects small amounts of TSH in the blood and measures thyroid activity. Another blood test used to diagnose Graves’ disease measures T3 uptake and free T4 (thyroxine) levels. The physician looks for below-normal levels of TSH, normal to elevated levels of T4 and elevated levels of T3. The physician may order a radioactive iodine uptake test to make an accurate diagnosis of Graves’ disease. This test measures the amount of iodine the thyroid collects from the blood. High levels of iodine uptake can indicate Graves’ disease. A thyroid scan can show where and how iodine is distribute in the thyroid.

There are three options for treating Graves’ disease. Radioiodine therapy is used most often. Patients take an oral dose of radioactive iodine-131, which destroys the cells of the thyroid gland but leads to hypothyroidism. Synthetic thyroid hormone replaces the natural thyroid hormone. Antithyroid medications such as Propylthiouracil (PTU) and methimazole are also prescribed, often as a supplement after radioiodine therapy or before surgery. Pregnant and nursing women with Graves’ disease are treated with antithyroid medication since they cannot take radioiodine therapy. Using anthithyroid medication can prevent thyroid storm or thyrotoxic crisis, an acute, life-threatening, hypermetabolic state induced by excessive release of thyroid hormone in individuals with hyperthyroidism (thyrotoxicosis).

Surgery is the final option for treating Graves’ disease. This may involve the removal of the entire thyroid (thyroidectomy). In this instance, patients must take thyroid hormone medication for the remainder of their lives. Potential complications of surgery include damage to the laryngeal nerve, which lies near the thyroid, and possible effects on the adjacent parathyroid glands.

Source: The American Thyroid Association (www.thyroid.org)

By Tanya J. Tyler, Associate Editor



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