The thyroid gland lies in the neck. It is part of the endocrine system and produces a substance (thyroid hormone) that helps control metabolism. A thyroid nodule is a lump of tissue on this gland. Nodules may be caused by an infection, cyst, benign tumor, or malignant tumor of the thyroid. Most nodules are benign tumors or cysts filled with fluid. Because some thyroid nodules are cancerous, all nodules should be examined.
Most people don’t know that they have a nodule. Some people may have no symptoms. Others may feel or see a soft, painless swelling near the thyroid in the neck. Most nodules are benign, cold (inactive) nodules, with no effect on health. Hot (overactive) nodules cause anxiety, sweating, weight loss, hunger, and tremor by producing excess thyroid hormone (hyperthyroidism).
A rock-hard nodule that grows rapidly and causes a voice change (hoarseness) or swallowing difficulty suggests cancer and should be removed quickly.
A sonogram (a test that uses sound waves to make pictures of body parts) can tell whether nodules are present and whether a nodule is solid. Solid nodules may be cancerous.
Sometimes thyroid nodules can be seen on CT scans of the chest or neck done for other reasons. After nodules are found, two important questions need answers:
Thyroid function blood tests answer the first question. Most people have normal thyroid function.
A special test (radioactive iodine scan) can tell whether an overactive nodule is producing too much hormone and must be treated. This test is done only if the blood tests show an excess of thyroid hormone.
A health care provider will check a tissue sample (biopsy) of the nodule to see whether the nodule is benign or malignant if the thyroid function is normal. A fine-needle aspiration biopsy (FNAB) is used to get this sample. Using a needle passed into the nodule, the health care provider will collect cells from the thyroid gland and examine them under a microscope. Some thyroid nodules may be too small to biopsy and your health care provider may choose to repeat the thyroid sonogram a few months later.
Most nodules are benign and do not need any treatment. Benign solid nodules are sometimes treated with thyroid supplements (levothyroxine) that help prevent nodule growth. Nodules that contain only fluid are drained during the FNAB.
Surgery may be needed to remove very large nodules if they press on blood vessels or other tissues in the neck. Malignant nodules are removed with surgery. In some cases, if the whole tumor cannot be removed, radioactive iodine can destroy remaining cancer cells. This treatment also destroys normal thyroid cells, so after treatment most people develop an underactive thyroid (hypothyroidism) and need medicine to replace thyroid hormone.
Complications after surgery include bleeding, infection, low calcium levels from damage to the parathyroid glands near the thyroid during surgery, or damage to vocal cords.
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