The thyroid gland is a butterfly-shaped organ and is composed of two cone-like lobes or wings, right and left which are connected via the isthmus. The lobes are small, around 3.5-4.5 cm in length, 1-2 cm wide, and 1-2 cm in thickness. The organ is situated in front side of the neck, lying against and around our voicebox and windpipe. It also reaches our foodpipe in back side. It is difficult to demarcate the gland’s upper and lower border with vertebral levels because it moves position in relation to these during swallowing. Occasionally (40-50% of people) a third lobe called the pyramidal lobe is also present. It is of conical shape and extends from the upper part of the isthmus to the hyoid bone.
The thyroid gland is covered in front with infrahyoid muscles and on sides with the sternocleidomastoid muscle also known as sternomastoid muscle.
Between the thyroid capsule and thyroid gland, there are on each side two parathyroid glands. These parathyroid glands control calcium levels in body.
Two main nerves related to voice lie in close vicinity to thyroid gland- Recurrent Laryngeal Nerve and External Branch of Superior Laryngeal Nerve.
The importance of these nerves and parathyroid glands come when thyroid is being operated; its very important to save these structures while operation.