Ectopic Thyroid Tissue
Ectopic thyroid tissue is functioning or nonfunctioning thyroid tissue located outside the normal position of the thyroid gland in the front of the neck. The most common site is at the back of the tongue (lingual thyroid), but ectopic thyroid tissue can occur anywhere along the path the thyroid follows during fetal development—from the base of the tongue to the upper chest—and, less commonly, in other locations. In some patients, the ectopic tissue is the only functioning thyroid they have, while others also have a normally located thyroid. Ultrasound, thyroid function tests, and, in selected cases, radioactive iodine imaging and cross-sectional imaging are central to diagnosis and management.
What is it?
The thyroid is a butterfly-shaped gland in the front of the neck that produces thyroid hormones, which regulate metabolism, heart rate, body temperature, and many other processes. During fetal development, the thyroid begins as a small group of cells at the base of the tongue and gradually descends through the neck to its normal position in front of the trachea below the larynx. Ectopic thyroid tissue is functioning or nonfunctioning thyroid tissue located outside this normal position because of abnormal migration during development.
Ectopic thyroid tissue can occur anywhere along the path of thyroid descent (the “thyroglossal duct”) and, less commonly, in other locations. The most common form is lingual thyroid, in which the tissue remains at the back of the tongue near the foramen cecum. Other described locations include sublingual and suprahyoid positions in the upper neck, thyroid tissue along the thyroglossal duct (sometimes producing a thyroglossal duct cyst), and lower cervical or substernal locations. Rarer locations include the mediastinum, lateral neck (which can raise questions about the possibility of metastatic thyroid cancer and requires careful evaluation), and even more distant sites such as the ovaries (struma ovarii, a specialized entity beyond the scope of this page). The presence of ectopic thyroid tissue does not always mean that a normally located thyroid is absent; the two can coexist, and evaluation is essential in either case.
Ectopic thyroid tissue may function normally, be underactive, or, less commonly, be overactive. In many patients with lingual or other high cervical ectopic thyroid tissue, the ectopic tissue is the only functioning thyroid the person has, and its removal without adequate management can cause severe hypothyroidism. This is one reason why careful evaluation before any intervention is essential.
Symptoms and clinical presentation vary widely. Many patients with small ectopic thyroid tissue have no symptoms and are identified incidentally during evaluation for another reason. Symptoms most commonly develop when the tissue enlarges due to increased thyroid demand (such as during puberty, pregnancy, or illness) or long-standing hypothyroidism that increases TSH stimulation. Possible features include fullness at the back of the tongue or in the neck, difficulty swallowing, muffled voice, sensation of a lump, snoring or upper airway obstruction, and, less commonly, bleeding from the surface of the tissue. Symptoms of hypothyroidism—such as fatigue, weight gain, cold intolerance, constipation, dry skin, and, in children, growth or developmental issues—may also be present. Hyperthyroidism from ectopic thyroid tissue is rare. In children, ectopic thyroid tissue is one of the causes of congenital hypothyroidism identified through newborn screening programs.
Diagnosis combines clinical assessment, laboratory testing, and imaging. Physical examination and, when the tongue base is involved, laryngoscopy can identify a characteristic mass. Blood tests typically include TSH and free T4 (and, when needed, free T3), which help assess thyroid function; thyroglobulin and thyroid antibodies may be measured in selected patients. Ultrasound of the neck is a central initial test to determine whether a normally located thyroid gland is present. Radioactive iodine imaging or Tc-99m pertechnetate scanning is highly useful for confirming that the tissue in question is functioning thyroid tissue by demonstrating uptake in the unusual location; scanning also shows whether a normal thyroid is present. CT or MRI is used in selected cases, particularly when detailed anatomy is needed for treatment planning, when substernal extension or airway involvement is a concern, or when the diagnosis is unclear. Biopsy is generally used cautiously and only after thyroid function and normal thyroid presence have been assessed, since the possibility of only one functioning thyroid source (in the ectopic location) has important implications for any intervention.
Thyroid cancer can rarely arise in ectopic thyroid tissue and is treated using standard thyroid cancer principles when identified. Isolated lateral neck thyroid tissue should not be assumed to represent benign ectopy without careful evaluation because the possibility of metastatic thyroid cancer from an occult primary tumor must be considered.
Important to Know
Management of ectopic thyroid tissue depends on its location, size, function, symptoms, and whether a normally located thyroid is present. Care is best coordinated by primary care clinicians, endocrinologists, otolaryngologists (ENT), radiologists, nuclear medicine specialists, and, in selected patients, general or head and neck surgeons and pediatric specialists.
For asymptomatic patients with ectopic thyroid tissue and normal thyroid function, observation is often appropriate. Periodic clinical assessment, thyroid function tests, and, when relevant, imaging are used to monitor for changes over time. The frequency of follow-up is individualized.
Levothyroxine (thyroid hormone replacement) is the mainstay of treatment for hypothyroidism, which is common in patients with ectopic thyroid tissue—particularly lingual thyroid—because the ectopic tissue is often insufficient to meet the body’s needs. In addition to treating hypothyroidism, levothyroxine can also suppress TSH and, in many cases, reduce the size of the ectopic tissue over time, which may relieve symptoms. Dose is adjusted based on TSH and clinical response and typically requires periodic monitoring.
Radioactive iodine ablation is used in selected patients with symptomatic ectopic thyroid tissue that concentrates iodine, particularly for lingual thyroid causing significant symptoms. It can gradually reduce the size of the ectopic tissue and improve symptoms. Because ablation eliminates the ectopic tissue’s ability to produce thyroid hormone, lifelong thyroid hormone replacement is typically needed afterward, especially if the ectopic tissue was the only functioning thyroid.
Surgical treatment is considered in specific situations. Indications may include significant symptoms not responding to medical or radioactive iodine therapy; severe or progressive airway obstruction, swallowing difficulty, or bleeding; suspicion of malignancy; or diagnostic uncertainty when other approaches have not established the diagnosis. Surgery is highly individualized and depends on the location of the tissue. Approaches for lingual thyroid may include transoral removal, midline transcervical approaches, or robotic-assisted techniques, depending on the surgeon’s experience. Surgery for other ectopic locations is planned based on anatomy and can range from focused excision to more extensive procedures. In selected cases, autotransplantation of removed ectopic thyroid tissue has been described, although this is not a standard practice at most centers.
Before any surgical intervention, it is essential to determine whether a normally located thyroid exists and whether the ectopic tissue is functioning. Removing the only functioning thyroid tissue can cause severe hypothyroidism, and patients must be prepared with a clear plan for thyroid hormone replacement.
For patients with ectopic thyroid tissue identified through newborn screening for congenital hypothyroidism, prompt initiation of thyroid hormone replacement is important to support normal growth and neurological development. Coordinated care with pediatric endocrinology is essential.
Care during pregnancy requires special attention. Pregnancy increases thyroid hormone demand, and women with ectopic thyroid tissue may need adjustments in thyroid hormone replacement doses under specialist guidance. Symptoms related to enlargement of ectopic tissue may develop or worsen during pregnancy.
For patients with suspected or confirmed thyroid cancer arising in ectopic thyroid tissue, treatment follows standard thyroid cancer principles and is best coordinated by multidisciplinary teams that include endocrinology, endocrine or head and neck surgery, radiology, pathology, nuclear medicine, and oncology. Isolated lateral neck thyroid tissue is generally approached with particular care, since metastatic thyroid cancer from an occult primary must be considered until proven otherwise.
Care is typically coordinated by primary care clinicians, endocrinologists, ENT specialists, radiologists, nuclear medicine specialists, and, when relevant, surgeons and pediatric specialists. Imaging and laboratory findings are interpreted alongside the patient’s symptoms, examination, and broader clinical context rather than in isolation.
Patient education plays an important role. Understanding the diagnosis, the rationale for recommended monitoring or treatment, the importance of medication adherence when thyroid hormone replacement is needed, warning signs of complications, and the potential impact of pregnancy or other life events on thyroid function all contribute to better outcomes.
Red flag symptoms include rapid enlargement of a mass at the back of the tongue or in the neck; new or progressive difficulty breathing or stridor; difficulty swallowing solids or liquids; significant bleeding from the mouth or throat; severe pain in the neck or tongue; high fever with signs of severe infection; symptoms of severe hypothyroidism (such as extreme fatigue, confusion, hypothermia, or slowed breathing, which may indicate myxedema) or severe hyperthyroidism (such as severe palpitations, chest pain, marked weight loss, severe tremor, agitation, or high fever with confusion, which may indicate thyroid storm); or sudden severe symptoms of unknown cause. These warrant prompt or urgent medical evaluation, as they may indicate airway compromise, hemorrhage, thyroid emergencies, or other serious complications.