The inferior thyroid vein is a venous blood vessel that drains the thyroid gland. It arises from small veins that are found on the lateral surface of the thyroid gland forming the thyroid venous plexus. The inferior thyroid vein emerges from the inferior aspect of the gland at the lower border of the isthmus.

The number of thyroid veins can vary, and a person can have even up to five veins. The inferior thyroid veins are highly variable not only in their number but also in their course and termination sites.

After the inferior thyroid veins arise, they descend toward the brachiocephalic veins. These veins travel over the anterior surface of the trachea and form numerous anastomoses that altogether form a venous plexus known as the pretracheal venous plexus (plexus thyroideus impar).

The inferior thyroid veins usually terminate in the right or left brachiocephalic veins or at the confluence site of the right and left brachiocephalic veins. Some studies have shown that the inferior thyroid veins may drain into the internal jugular veins.

Most commonly, the left inferior thyroid vein flows into the left brachiocephalic vein, while the right inferior thyroid vein flows into the right brachiocephalic vein. However, both veins may alternatively terminate into only one of the brachiocephalic veins.

Additionally, the thyroid veins sometimes can form a common trunk called the inferior thyroid ima vein before joining the brachiocephalic vein. Most commonly, the inferior thyroid ima vein empties into the left brachiocephalic vein.

The main tributaries of the inferior thyroid veins are as follows:

Overall, the inferior thyroid veins drain blood from the inferior and medial aspects of the thyroid gland, the distal part of the larynx, the proximal part of the trachea and the cervical portion of the esophagus.

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Inferior thyroid vein