The thyroid gland is an endocrine organ of the body that regulates body balance. The thyroid gland is the largest endocrine gland and is located in the anterior part of the neck, attached to the side of the larynx and trachea. The thyroid gland is composed of the left and right lobes, the isthmus based on the cone lobe. During swallowing, the thyroid gland can move up and down with the larynx. The thyroid isthmus connects the left and right lobes and is located in front of the 1st to 3rd tracheal rings. The thyroid gland has two layers of perithelium, the thyroid capsule and the fibrous capsule. Because the thyroid capsule and the fibrous capsule are loosely connected to each other and can be easily separated, it is clinically possible to perform an intracapsular thyroidectomy. The thyroid levator muscle has the function of lifting the thyroid gland. The parafollicular cells or lucent cells in the thyroid gland produce calcitonin. It has a hypocalcemic effect when blood calcium is elevated. The thyroid gland is supplied with blood by one pair each of the superior thyroid artery and the inferior thyroid artery. The thyroid gland is very vascular and a murmur or tremor can often be heard or felt in the neck of patients with diffuse thyroid disease. The thyroid gland receives both sympathetic and parasympathetic innervation, with the sympathetic nerves mainly coming from the postganglionic fibers of the sympathetic ganglion in the neck and the parasympathetic nerves coming from the vagus nerve. The thyroid gland plays a vital role in the body and needs to be checked regularly.