Most thyroid nodules don't cause symptoms. But some nodules get so large that they can:

• Be felt.
• Be seen, often as a swelling at the base of the neck.
• Press on the windpipe. That can cause shortness of breath.
• Press on the tube that connects the throat to the stomach, called the esophagus. This can make it hard to swallow.

Some thyroid nodules can make too much of a hormone called thyroxine. The extra thyroxine can cause a condition called hyperthyroidism. It has symptoms such as:

• Unexplained weight loss.
• Increased sweating.
• Tremor.
• Feeling nervous.
• Rapid or irregular heartbeat.

Most thyroid nodules are not cancer and don't cause problems. But if you see swelling in your neck, especially if it affects breathing or swallowing, see a healthcare professional right away. This is to make sure the swelling isn't related to cancer.

Also see a healthcare professional if you have any symptoms of hyperthyroidism.

Several conditions can cause nodules in the thyroid gland, including:

• Overgrowth of thyroid tissue. This is sometimes called a thyroid adenoma. It's unclear why this happens, but it isn't cancer. And it's not thought to be serious unless its size causes symptoms that bother you. Some thyroid adenomas can lead to hyperthyroidism.
• Thyroid cyst. Fluid-filled spaces in the thyroid called cysts most often come from thyroid adenomas that break down. Often, solid parts are mixed with fluid in thyroid cysts. Cysts usually are not cancer. But they sometimes have solid parts that are cancer.
• Multinodular goiter. A goiter is an enlarged thyroid gland. Lack of iodine in the diet or a thyroid problem can cause a goiter. A multinodular goiter has more than one nodule within the goiter. Its cause isn't clear.

• Thyroid cancer. The chances that a nodule is a cancer are small. But see a healthcare professional for a nodule that is large and hard or causes pain or discomfort.

  Factors that increase your risk of thyroid cancer include having a family history of thyroid or other endocrine cancers. A history of radiation from medical therapy or from nuclear fallout also raises the risk.

• Iodine deficiency. Lack of iodine in your diet sometimes can cause thyroid nodules. But iodine deficiency isn't common in the United States. That's because iodine is added to table salt and other foods in the United States.

Factors that raise the risk of getting thyroid nodules include:

• Being female. Females are more likely to get thyroid nodules than males are. But males are more likely to have cancer in the nodules.
• Older age. Thyroid nodules get more common with age.
• Not enough iodine in the diet. This isn't common in the United States and other countries where iodine is added to table salt.
• Childhood contact with radiation. This can be from radiation treatments to the head and neck or from nuclear fallout.

Complications of some thyroid nodules include:

• Problems swallowing or breathing. Large nodules or a multinodular goiter can cause neck discomfort and get in the way of swallowing or breathing.

• Hyperthyroidism. Problems can happen when a nodule or goiter makes thyroid hormone. This leads to too much of the hormone in the body. Hyperthyroidism can cause weight loss, muscle weakness, not being able to handle heat, and being anxious or cranky. Complications of hyperthyroidism include an irregular heartbeat and thinning bones.

• Problems related to thyroid nodule surgery. If you have surgery to remove a nodule, you may need to take thyroid hormone replacement therapy for the rest of your life.

Your healthcare professional checks the lump or nodule in your neck to rule out cancer and to make sure your thyroid is working as it should. Tests might include:

• Thyroid function tests. These tests measure blood levels of thyroid-stimulating hormone (TSH) and hormones your thyroid gland makes. These tests can show if you have too much or too little thyroid hormone.

• Ultrasound. This test uses sound waves to make images of your thyroid gland. A thyroid ultrasound shows the shape and structure of nodules.

• Fine-needle aspiration biopsy. A biopsy of nodules can make sure there's no cancer. During the procedure, a healthcare professional puts a very thin needle in the nodule and removes a sample of cells. Ultrasound imaging might guide the needle.

  The biopsy most often is done in a healthcare professional's office. It takes about 20 minutes. There are few risks. The samples go to a lab for study under a microscope.

• Thyroid scan. A thyroid scan tells more about the thyroid nodules. During this test, radioactive iodine is put into a vein in your arm. You then lie on a table while a special camera makes an image of your thyroid on a computer screen.

  Nodules that make too much thyroid hormone, called hot nodules, show up on the scan. They take up more of the iodine than typical thyroid tissue does. Hot nodules are rarely cancer.

  Some nodules take up less of the iodine. They're called cold nodules. They can be cancer. But a thyroid scan can't tell which cold nodules are cancer and which are not.

Treatment depends on the type of thyroid nodule you have.

Treating thyroid nodules that aren't cancer

Treatment options include:

• Watchful waiting. This means simply watching your condition. It often means having a physical exam and thyroid function tests regularly. It also may include an ultrasound. You'll likely have another biopsy if the nodule grows. If your thyroid nodule doesn't change, you might not need treatment.

• Surgery. A nodule that isn't cancer might need surgery if it's large enough to make it hard to breathe or swallow. People with large multinodular goiters might need surgery. That's especially true if the goiters block airways, the esophagus or blood vessels.

  If it's not clear from biopsy results whether a nodule is cancer, the nodule might need to be removed. Then it can be studied further for signs of cancer.

Treating nodules that cause hyperthyroidism

If a thyroid nodule is making too much thyroid hormone, you might need treatment for hyperthyroidism. This may include:

• Radioactive iodine. You take radioactive iodine in capsule or liquid form. Your thyroid gland takes in radioactive iodine, which causes the nodules to shrink. Symptoms of hyperthyroidism go away, usually within two to three months.
• Anti-thyroid medications. Sometimes, an anti-thyroid medicine such as methimazole can ease symptoms of hyperthyroidism. Treatment is most often long term. Rarely, it can have serious side effects on your liver. Talk to your healthcare professional about the risks and benefits.
• Surgery. If you can't take radioactive iodine or anti-thyroid medicines, surgery to remove the thyroid nodule might be an option. Talk to your healthcare professional about the risks and benefits.

Treating nodules that are cancer

Treatment for a nodule that is cancer usually involves surgery.

• Keeping watch. Very small cancers have a low risk of growing, so your healthcare professional might watch the nodules for a time. A thyroid specialist may help you make this choice. Keeping watch includes having ultrasounds and blood tests.

• Surgery. Surgical removal of nodules that are cancer is the common treatment. In the past, it was standard to remove most of the thyroid tissue. This is called near-total thyroidectomy.

  Today, taking out only half the thyroid might be an option. This is called a partial thyroidectomy or lobectomy. Its use depends on the extent of the cancer.

  Risks of thyroid surgery include damage to the nerve that controls the vocal cords and damage to four tiny glands on the back of the thyroid. They are called the parathyroid glands. These glands help control the body's levels of minerals, such as calcium.

  After a thyroid surgery, you'll need lifelong treatment with a medicine called levothyroxine. It gives your body thyroid hormone. Your thyroid specialist works with you to find the right amount to take.

• Alcohol ablation. This is another option for treating certain small nodules that are cancer. Alcohol ablation involves injecting a small amount of alcohol in the thyroid nodule to destroy it. This often takes several sessions. Other types of ablations also might be used.

Often, thyroid nodules are found during routine medical exams. But if you see or feel a thyroid nodule in the middle of your lower neck, just above your breastbone, have your primary care professional look at the lump.

If you have a thyroid nodule, you'll likely be sent to a specialist in disorders of glands that secrete hormones. That specialist is called an endocrinologist. Here are ways to get the most from your appointment:

• Be aware of pre-appointment restrictions. When you make your appointment, ask if there's anything you need to do before the appointment to prepare for tests.
• Write down all symptoms you have, and when they began.
• Make a list of important medical information. This includes recent surgeries and other conditions you've had. List all medicines and supplements you take, including doses.
• Make note of your personal and family medical history. Include whether you've had thyroid disorders or thyroid cancer. Note any contact with radiation you've had at any time in your life.
• Write down questions to ask your healthcare professional. For instance, if your nodules don't cause problems, do you need treatment? What are the treatment options?