The thyroid, a small gland located at the front of the throat, produces hormones that influence the function of every cell in the body. Thyroxine, triiodothyronine and calcitonin are three hormones that the thyroid gland produces. These hormones are essential in regulating blood calcium levels and metabolism. An enlarged thyroid gland can change the levels of hormone produced in the gland, causing overproduction, underproduction or no production of these essential hormones. A number of different factors cause an enlarged thyroid gland, or goiter.
Autoimmune Disease
Graves’ disease and Hashimoto’s thyroiditis are two of the most common thyroid disorders in the United States. These diseases are autoimmune diseases, which result when the body’s immune system mounts a defensive attack against its own healthy thyroid tissues.
Graves’ disease causes an increased production of thyroxine, a condition that is also known as hyperthyroidism. The overworked thyroid gland swells and enlarges in this condition.
Hashimoto’s thyroiditis occurs when inflammation damages the thyroid, lessening its ability to produce hormone. When thyroid hormone levels drop, the pituitary gland sends thyroid-stimulating hormone, or TSH, to prompt increased production. The thyroid gland, unable to respond, becomes swollen, according to the Mayo Clinic.
Iodine Insufficiency
Iodine is a vital component in the body's synthesis of thyroid hormone. People must obtain iodine from dietary sources. When too little iodine is available, the thyroid gland responds to the body’s unmet need for thyroid hormones by growing larger, a condition that Medline Plus calls colloid goiter.
The iodine-rich soils near the sea usually preclude the possibility of iodine deficiency in coastal areas, but communities further inland require supplementation to maintain sufficient iodine levels.The addition of iodine to salt has eliminated iodine deficiency in much of the developed world.
Thyroid Nodules
Sometimes abnormal cell growth causes lumps, called nodules, to form in the thyroid gland and enlarge it. Most thyroid nodules are benign; only approximately 10 percent are cancerous. Adenoma is the most common benign nodule found in the thyroid gland. Benign nodules can be the result of inflammation, genetics or iodine deficiency.
Malignant thyroid nodules are rare and in most cases curable, according to the American Thyroid Association, but patients should have them surgically removed. Biopsies are used to determine whether a nodule is malignant. Malignancy is detected in about 5 percent of thyroid nodules. Papillary cancer is one of the most commonly diagnosed types of thyroid nodule malignancy.
