The inferior thyroid vein may refer to any of the two, three or four veins that make up the venous plexus, an intricate system of interconnected veins that drain blood away from the thyroid gland. The thyroid gland is located in the front of the neck, just above the center of the collarbone. Among other functions, the thyroid determines how quickly the body produces or makes energy, controls the body's sensitivity or response to hormones, and creates proteins.

Two veins divide from the venous plexus: the left vein merges with the brachiocephalic artery while the right vein merges with the superior vena cava, the major vein directly connected to the heart.

Specifically, the vein functions to carry deoxygenated blood from the thyroid gland, where it is transported back to the heart. Because the thyroid gland is a very vascular organ (this means it contains many blood vessels), the vein circulates a huge amount of blood, together with the thyroid arteries.

Since the venous plexus is located in front of the trachea (windpipe), severe trauma to the frontal part of the neck may cause at least one inferior thyroid vein to rupture or break, leading to hemorrhage (bleeding). Surgical procedures of the trachea are performed with the utmost caution in order to prevent such incidences.