The thyroid gland is a small butterfly-shaped gland in the neck found just in front of the trachea (windpipe).
Thyroid nodules are fluid-containing or solid lumps that arise in the thyroid gland. Most of these nodules are not serious and do not cause any symptoms. They may be incidentally found when scans are performed for other reasons.
Thyroid nodules are four times more common in women than in men.
Thyroid nodules can be caused by an overgrowth of normal thyroid tissue (and adenoma), thyroid cysts (fluid-filled spaces that arise when adenomas degenerate), a multinodular goitre, which can be caused by an iodine deficiency in the diet or by another thyroid disorder. Goitres are more common in parts of the world where they have low levels of iodine in the diet. Since 2009, it has been a requirement in Australia for bread manufacturers to make bread with iodine-enriched salt. Other foods, such as seafood, eggs, milk, and milk products, contain iodine.
A small percentage of thyroid nodules are thyroid cancers. A family history of thyroid or endocrine cancers or childhood radiation exposure increases the risk of developing thyroid cancer.
Other conditions, such as Hashimoto’s thyroiditis, can cause thyroid inflammation and result in enlarged nodules.
Thyroid nodules might cause symptoms if they become large enough. Symptoms may include feeling a lump in the neck or swelling at the base of the neck. If the nodule is big enough it may press on the trachea or the oesophagus, causing shortness of breath or trouble swallowing. If a nodule produces too much thyroid hormone, additional symptoms can include unexplained weight loss, sweating, shakes, restlessness, and an irregular heart rhythm.
Some thyroid nodules can be detected upon physical examination, if they are large enough. Further tests are required to better characterise thyroid nodules, usually consisting of ultrasound scans, blood tests, and sometimes a fine-needle aspiration (FNA) biopsy.