- The thyroglossal duct, which develops from the midline of the pharynx, extends downward in front of the pharynx. The distal end of this diverticulum enlarges to form the thyroid gland.
- The thyroid gland migrates caudally to its final position in the neck, but remains connected to the tongue via the thyroglossal duct. This duct is eventually obliterated.
- The foramen cecum is a normal remnant of the thyroglossal duct.
Lingual thyroid.
- The thyroid gland is normally located in the lower anterior neck, in front of the upper trachea and larynx.
- The thyroid gland forms as an outpouching, or evagination, of the pharyngeal epithelium that descends to the lower anterior neck.
- The remaining part of the evagination forms the thyroglossal duct, which extends from the foramen cecum on the tongue's dorsal surface to the superior border of the thyroid isthmus.
- Ectopic thyroid can form at any part along the thyroglossal duct's usual path due to failed migration. If the thyroid doesn't migrate downward, it can form within the tongue, called a "lingual thyroid". Occasionally, this lingual thyroid is the only thyroid tissue in the body. If it is removed, significant hypothyroidism can occur.
- Surgeons should exercise caution when removing any mass along the thyroglossal duct's usual path, as it could be the patient's only thyroid tissue.
- Other endocrine disorders can also result from defective migration**. Kallmann's syndrome** is described as the failure of GnRH-secreting neurons to migrate from the olfactory lobes to the hypothalamus. Cryptorchidism is the failure of the testes to migrate from their intra-abdominal location to the scrotum.
- Video about Kallmann’s syndrome
Thyroglossal cyst.