What is thyroglossal duct surgery done for?

To remove the cyst: The surgery is done to remove the cyst which is causing a change in thyroid levels.

Thyroglossal : This procedure is performed to removed the cyst called thyroglossal. It is removed when it is causing trouble.

A thyroglossal duct: ... Cyst/sinus is a congenital anomaly in which a cyst/sinus tract is present in the middle of the front of the upper neck . It extends from beneath the skin thru the middle of the hyoid bone up to the base of the tongue. The natural history is to repeatedly become infected. Excision is therefore indicated & must include the middle of the hyoid bone & the entire sinus tract to prevent recurrence.