 It differs in size and ranges from as small as accessory thyroid arteries to the size of primary thyroid vessels. The diameter of the lumen of the artery ranges from 3 – 5 millimetres (0.12 – 0.20 in). The artery may be present as an accessory thyroid artery but sometimes appears to compensate for incompetence or absence of one or more main thyroid vessels. Since it begins from below the thyroid gland and ascends upwards, it is mostly associated with absence or reduced size of the inferior thyroid arteries. In such cases, it is known as the accessory inferior thyroid artery. In rare cases, the artery has been seen to be compensating for absence of one or both superior thyroid arteries.
