Thyroid nodules are solid or fluid-filled lumps that form within your thyroid, a small gland located at the base of your neck, just above your breastbone.
The great majority of thyroid nodules aren’t serious and don’t cause symptoms. Thyroid cancer accounts for only a small percentage of thyroid nodules.
You often won’t know you have a thyroid nodule until your doctor discovers it during a routine medical exam. Some thyroid nodules, however, may become large enough to be visible or make it difficult to swallow or breathe.
Treatment options depend on the type of thyroid nodule you have.
Several conditions can cause nodules to develop in your thyroid gland:
- Iodine deficiency. Lack of iodine in your diet can sometimes cause your thyroid gland to develop thyroid nodules. But iodine deficiency is uncommon in the United States, where iodine is routinely added to table salt and other foods.
- Overgrowth of normal thyroid tissue. Why this occurs isn’t clear, but such a growth — which is sometimes referred to as a thyroid adenoma — is noncancerous and isn’t considered serious unless it causes bothersome symptoms from its size. Some thyroid adenomas (autonomous or hyperfunctioning thyroid nodules) produce thyroid hormones outside of your pituitary gland’s normal regulatory influence, leading to an overproduction of thyroid hormones (hyperthyroidism).
- Thyroid cyst. Fluid-filled cavities (cysts) in the thyroid most commonly result from degenerating thyroid adenomas. Often, solid components are mixed with fluid in thyroid cysts. Cysts are usually benign, but they occasionally contain malignant solid components.
- Chronic inflammation of the thyroid (thyroiditis).Hashimoto’s disease, a thyroid disorder, can cause thyroid inflammation resulting in nodular enlargement. This often is associated with reduced thyroid gland activity (hypothyroidism).
- Multinodular goiter. “Goiter” is a term used to describe any enlargement of the thyroid gland, which can be caused by iodine deficiency or a thyroid disorder. A multinodular goiter contains multiple distinct nodules within the goiter, but its cause is less clear.
- Thyroid cancer. Although the chances that a nodule is malignant are small, you’re at higher risk if you have a family history of thyroid or other endocrine cancers, are younger than 30 or older than 60, are a man, or have a history of radiation exposure, particularly to the head and neck. A nodule that is large and hard or causes pain or discomfort is more worrisome in terms of malignancy.
Most thyroid nodules don’t cause signs or symptoms. Occasionally, however, some nodules become so large that they can:
- Be felt
- Be seen, often as a swelling at the base of your neck
- Press on your windpipe or esophagus, causing shortness of breath or difficulty swallowing
In some cases, thyroid nodules produce additional thyroxine, a hormone secreted by your thyroid gland. The extra thyroxine can cause symptoms of hyperthyroidism such as:
- Unexplained weight loss
- Intolerance to heat
- Rapid or irregular heartbeat
A few thyroid nodules are cancerous (malignant), but determining which nodules are malignant can’t be done by symptoms alone. Most cancerous thyroid nodules are slow growing and may be small when they’re discovered. Aggressive thyroid cancers are rare, but these nodules may be large, firm, fixed, and rapid growing.
When to see a doctor
Although most thyroid nodules are noncancerous (benign) and don’t cause problems, ask your doctor to evaluate any unusual swelling in your neck, especially if you have trouble breathing or swallowing. It’s important to evaluate the possibility of cancer.
Also seek medical care if you develop signs and symptoms of hyperthyroidism, such as:
- Sudden weight loss even though your appetite is normal or has increased
- A pounding heart
- Trouble sleeping
- Muscle weakness
- Nervousness or irritability