Goiter refers to an enlarged thyroid gland. It can occur in both hypothyroidism, as thyroid cells enlarge in their efforts to trap more iodine, and in hyperthyroid as thyroid cells elongate and swell due to to their vigourous assembly line production of thyroid hormone.
There are approximately 25 different types of goiter, depending on the type of pattern created when cells take up iodine and by characteristic changes in thyroid tissue. Goiters may also be nodular, having hot or cold nodules, or they may be vascular, with changes present in the veins and arteries that supply the thyroid gland. In Graves' disease, iodine distribution is even although the uptake of iodine is increased. For these reasons, goiter in Graves' disease is called "diffuse toxic goiter."
Why do some goiters continue to grow? In hypothyroidism due to iodine deficiency, goiters continue to enlarge as the cells try to pull in more iodine. In autoimmune thyroid disorders, including Graves' disease and Hashimoto's thyroiditis, thyroid growth immunoglobulins (TGI) are the primary cause of goiter enlargement. TGI stimulate thyroid cell growth, whereas thyroid stimulating immunoglobulins (TSI) cause excess thyroid hormone production. ♦
© 11 Mar 2006 Copyright by Elaine Moore