Tuesday, July 11, 2006

symptom thyroid : Other Less Common Causes of Hyperthyroidism

Hyperthyroidism can also be caused by a single nodule within the thyroid instead of the entire thyroid. As outlined in detail on our nodules page, thyroid nodules usually represent benign (non-cancerous) lumps or tumors in the gland. These nodules sometimes produce excessive amounts of thyroid hormones. This condition is called "toxic nodular goiter". The picture on the right is an iodine scan (also simply called a thyroid scan) which shows a normal sized thyroid gland (shaped like a butterfly). This scan is abnormal because a solitary "hot" nodule is located in the right lower lobe. This single nodule is comprised of thyroid cells which have lost their regulatory mechanism which dictates how much hormone to produce. Without this regulatory control, the cells in this nodule produce thyroid hormone at a dramatically increased rate causing the symptoms of hyperthyroidism. [As a point of reference, some nodules are "cold" since they don't produce any hormone at all. There is a picture of a cold nodule on the nodule page.]

Inflammation of the thyroid gland, called thyroiditis, can lead to the release of excess amounts of thyroid hormones that are normally stored in the gland. In subacute thyroiditis, the painful inflammation of the gland is believed to be caused by a virus, and the hyperthyroidism lasts a few weeks. A more common painless form of thyroiditis occurs in one out of 20 women, a few months after delivering a baby and is, therefore, known as postpartum thyroiditis. Although hyperthyroidism caused by thyroiditis causes the typical symptoms listed on our introduction to hyperthyroidism page, they generally last only a few weeks until the thyroid hormone stored in the gland has been exhausted. For more about thyroiditis see our page on this topic.

Hyperthyroidism can also occur in patients who take excessive doses of any of the available forms of thyroid hormone. This is a particular problem in patients who take forms of thyroid medication that contains T3, which is normally produced in relatively small amounts by the human thyroid gland. Other forms of hyperthyroidism are even rarer. It is important for your doctor to determine which form of hyperthyroidism you may have since the best treatment options will change depending on the underlying cause.

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