The thyroid gland (or simply the thyroid, latin: glandula thyreoidea) is an endocrine gland located in the anterior neck region in front of the throat below the prominence of the thyroid cartilage, adjacent to the larynx and trachea.
The thyroid is butterfly-shaped and consists of two large lateral lobes (each approximately 5 cm in length, 2.5 cm in width) connected by an isthmus, a thin band of thyroid tissue. The lobes of the thyroid lie on either side of the larynx and upper trachea.
The thyroid gland produces hormones thyroxine (T4) and triiodothyronine, which are essential to normal metabolism, growth, and development. The thyroid also makes the hormone called calcitonin, which is involved in calcium homeostasis.
The blood supply to the thyroid gland is mainly provided from the superior thyroid artery, a branch of the external carotid artery, and the inferior thyroid artery, which is a branch of the thyrocervical trunk. Individuals may have an anatomical variation, where blood supply to the thyroid comes from the thyroid ima artery, which depending on its embryonic development has a variable origin.
The thyroid gland is innervated by parasympathetic nerve fibers arising from the superior laryngeal nerve and the recurrent laryngeal nerve, and by sympathetic nerve fibers arising from the superior, middle and inferior cervical ganglia of the sympathetic trunk.