The thyroid gland begins at around the 3rd and 4th weeks of embryonic development as a proliferation of endodermal cells at the foramen cecum of the developing tongue. The gland descends to its final location anterior and inferior to the larynx but is still connected to the foramen cecum via the thyroglossal duct until that is broken down in the 5th week of development.

CLINICAL CORNER

Failure of the thyroid gland to migrate presents as a lingual thyroid where the gland remains at the base of the tongue. If the thyroglossal duct fails to atrophy, remnants can form thyroglossal cysts.