What Causes Thyroid Glands to Function Low?
- Thyroid Autoimmunity - Most cases of hypothyroidism in the more industrialized countries of the world is autoimmune thyroid disease. This means that the immune system attacks the thyroid gland using antibodies to attack proteins and other cells found in the gland that convert iodine into thyroid hormones. This disruption of thyroid hormone production results in the levels falling too low to regulate the metabolism of the body, which results in hypothyroidism or an "under-active thyroid." The most common type of thyroid autoimmunity resulting in low thyroid function is "Hashimoto's thyroiditis," an inflammatory condition of the gland resulting from destruction of the cells attacked by antibodies. Two other variants of autoimmune thyroiditis include Riedel's thyroiditis and Ord's thyroiditis but are less common than Hashimoto's thyroiditis. People with this type hypothyroidism are replaced with the low hormone by a daily dose of a drug containing the needed hormone called T4, which contains four iodine molecules and/or T3, which contains three iodine molecules.
- Iodine Deficiency - When the diet of an individual does not contain enough iodine, over time they can develop iodine deficiency hypothyroidism. Some countries, especially the less industrialized ones, have inadequate supplies of foods that are rich in iodine. The thyroid gland itself is mostly comprised of iodine and converts this element into the needed thyroid hormones that regulate bodily metabolism as described earlier. In industrialized countries, where iodized salt is widely available, this alone can supply the needed iodine for proper thyroid function. When low iodine intake is the cause of an under-functioning thyroid, it needs to be treated with a supplement that has the proper amount of iodine so that thyroid hormone production is restored to correct levels.
- Injury or Destruction of the Thyroid Gland - When a person's thyroid sustains an injury, enough active tissue in the gland may be diminished so that it cannot supply enough hormones that the body needs to sustain proper metabolism. In addition to traumatic accidents that can cause thyroid injuries, a person can also experience death of thyroid tissue from exposure to radiation. People who work at nuclear power plants or who work at x-ray laboratories can experience over-exposure to radiation if they do not take the proper safety measures or do not wear protective gear. When enough thyroid cells die, the gland may not be able to regenerate enough replacement cells for producing thyroid hormone at proper levels and hypothyroidism will result. The treatment for this type of destruction to thyroid tissue is the same as for autoimmune destruction of the gland and that is to administer a daily thyroid hormone replacement dose.
- Thyroid Nodules - Some people develop tumors on their thyroid glands and while the vast majority of these are non-malignant (containing no cancer) some grow to a significant size. When a nodule is larger in size it is more suspicious of malignancy and single nodules, rather than multiple ones, are also more suspicious. If cancer does develop, it can replace significant areas of hormone producing thyroid tissue, resulting in hypothyroidism. Some cancer treatments involving radiation therapy may require a delay in administering thyroid hormone replacement. Benign nodules that contain no cancer cells, which are referred to as "cold nodules," can also develop. These type can also replace areas of thyroid tissue so that less hormone is produced, resulting in under-functioning of the gland. Treatment for thyroid nodules may include removal of them and in some cases removal of one side of the gland (lobectomy) or the entire gland (thyroidectomy). If nodules are not large enough to cause problems with swallowing or breathing, they may need no treatment other than thyroid hormone replacement which can help shrink them and that also replaces low thyroid hormone (hypothyroidism).
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