Most thyroid nodules do not cause problems and are not cancerous. They are often hard to notice because they are so small. Lots of people have thyroid nodules that are never found or treated.

There are three kinds of thyroid nodules: solid nodules, nodules that are filled with fluid (cystic nodules), and nodules that are partially cystic. You can have one thyroid nodule or several thyroid nodules (multinodular goiter). You can also have some nodules that are solid and some that are cystic. Solid nodules may grow slowly over time. In rare cases, cystic nodules bleed, which can cause them to grow suddenly and become painful.

Thyroid nodules usually do not prevent the thyroid gland from doing its job. But sometimes a noncancerous thyroid nodule can cause:

• Hyperthyroidism. Hyperthyroidism happens when one or more nodules makes too much thyroid hormone. Hyperthyroidism is treated with antithyroid medicine, possibly radioactive iodine, and very rarely, surgery. Hyperthyroidism from thyroid nodules is not very common. It occurs in fewer than 1 out of 100 people who have thyroid nodules.² For more information on treating hyperthyroidism, see the topic Hyperthyroidism.
• Difficulty breathing or swallowing. Sometimes, one or more large nodules can press on your windpipe (trachea) or on your esophagus. These kinds of nodules have to be surgically removed.

Only about 5 out of 100 thyroid nodules are cancerous.¹Thyroid cancer is usually diagnosed and treated early, so most people do very well. For more information, see the topic Thyroid Cancer.

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