A thyroid cyst is a type of thyroid nodule filled or partially filled with fluid, according to Cleveland Clinic. Cysts form inside the thyroid gland.
Thyroid nodules, including thyroid cysts, form when thyroid tissue begins to inexplicably grow, notes Cleveland Clinic. Cancer may cause the growth of thyroid nodules, although cancer causes less than 5 percent of all thyroid nodules.
Most thyroid nodules, including thyroid cysts, do not cause any symptoms, advises Cleveland Clinic. However, if cysts or other types of nodules become large, they can press on other neck structures, causing symptoms such as difficulty breathing or swallowing, voice changes, hoarseness and pain in the neck. Goiter, which is an enlargement of the thyroid gland, can also develop.
It is also possible for thyroid nodules to cause hyperthyroid symptoms, although this is not always the case, notes Cleveland Clinic. Symptoms of hyperthyroidism include weight loss, irregular menstrual periods, muscle tremors or weakness and nervousness. Other symptoms include difficulty sleeping, heat sensitivity, thinning hair and changes in appetite. Heart palpitations, flushing of the skin, shortness of breath and clammy or itchy skin are also possible.
Treatment for thyroid cysts ranges from watchful waiting and monitoring of the nodules to hormone suppression therapy and radioactive iodine treatments, notes Cleveland Clinic. In some instances, surgery is required for removal of nodules that are cancerous or large enough to cause other problems.