Thyroid cysts, also known as thyroid nodules, are small sacs filled with fluid or blood that grow on the thyroid. These sacs can also be filled with solid matter, which is sometimes an indicator of thyroid cancer. The thyroid is an endocrine gland located at the bottom of a person’s throat, at the trachea. As one of the most important glands in the human body, the thyroid is involved in many processes, including the body’s metabolism, protein production and the regulation of hormone production.
Thyroid cysts can be large enough for a person to view at the base of his or her neck. A person with larger cysts is more likely to have symptoms that involve difficulty swallowing, becoming hoarse or experiencing trouble breathing due to the cyst pressing on the larynx, esophagus or trachea. Some people may experience tenderness or pain in the area of the lump as well. Thyroid cysts can also cause the gland to over produce the thyroid hormone, a condition called hyperthyroidism, or under produce the hormone, a condition called hypothyroidism. Small cysts can be smaller than about 0.1 inches (3 millimeters), and these small nodules will usually go unnoticed because they rarely produce any symptoms.
A physician carefully evaluates the thyroid and the cysts to determine how many there are and if the surrounding lymph nodes are abnormal, which could indicate cancer. The physician usually orders blood tests to determine the hormone levels the thyroid is producing, and he or she might also complete an ultrasound at the base of the neck to examine the cysts and look for masses. A fine-needle aspiration biopsy may also be performed to determine if the cysts are benign or if they could be cancerous. If the results are suspicious or the cysts are affecting other organs in the throat, the person will most likely need to have surgery to remove the cysts.
If the thyroid cysts are determined to be benign, a physician typically continues monitoring the thyroid for growth or abnormalities. A doctor may feel that shrinking the cysts is necessary, and he or she may prescribe a thyroid hormone suppression therapy or a regime of radioactive iodine. Only about 5 percent of benign cysts develop into cancerous tissue.
There is not a definitive cause for thyroid cysts, but many physicians believe they develop more frequently in people who have an iodine deficiency or a genetic defect that affects the thyroid. Thyroid cysts are also more likely in someone with Hashimoto's disease, a condition that destroys the thyroid; with a hyperfunctioning thyroid; or a person who has had a multinodular goiter. Women and those who have a family history of thyroid problems are much more likely to develop cysts as well.