Citation, DOI & article data
An ectopic thyroid gland is one which is located in a location other than the normal position anterior to the laryngeal cartilages.
Ectopic tissue refers to the gland located outside its normal anatomical position whereas accessory tissue refers to extra tissue located remotely from a normally positioned gland 6,7.
During embryological development, the thyroid gland migrates down from the foramen cecum at the posterior aspect of the tongue to its permanent location in the infrahyoid neck. This normal migration can be halted at any point, or indeed can go 'off-target' with thyroid tissue coming to rest in unusual locations within the neck or elsewhere 4:
- lingual: base of tongue (90%)
- sublingual: below the tongue
- other sites, e.g. mediastinum (<1%), intratracheal
Thyroid tissue may also be present in the normal thyroid bed, so-called "dual ectopic thyroid" 4.
Congenital hypothyroidism is common in patients with ectopic thyroid, requiring life-long hormone replacement. While the mechanism is incompletely understood, it has been suggested that maternal antithyroid antibodies may disturb the gland's descent and predispose the child to the development of dysthyroidism 8.
As imaging findings (other than location) are identical irrespective of location, the discussion on ectopic thyroids is continued as part of the lingual thyroid article.
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