Computed tomography of the thyroid bone, before it loops posteriorly and inferiorly to the hyoid bone. Then it continues its descent into the infra-hyoid portion of the neck, anterior to the trachea, thyroid cartilage, and thyroid membrane. Any thyroid residual along the descent course may lead to the development of ectopic thyroid glands. Thyroid carcinomas, thyroiditis, and goiter may develop within any ectopic thyroid tissue. Thyroid scanning with technetium-99 m (Tc99m) plays an important role in detecting orthotopic and ectopic thyroid tissue. Both CT scans and US can help detect ectopic tissue when a lesion demonstrates imaging and enhancement characteristics of thyroid tissue. The absence
Thyroid dysgenesis Thyroid dysgenesis Thyroid dysgenesis or thyroid agenesis is a cause of congenital hypothyroidism where the thyroid is missing, ectopic, or severely underdeveloped. It should not be confused with iodine deficiency, or with other forms of congenital hypothyroidism, such as thyroid dyshormonogenesis, where the thyroid is present but not functioning correctly. Congenital hypothyroidism caused by thyroid dysgenesis can be associated with PAX8. An "ectopic thyroid", also called "accessory thyroid gland", is a form of thyroid dysgenesis in which an entire or parts of the thyroid located in another part of the body than what is the usual case. A completely ectopic