Location: Located in the lower part of the anterior cervical larynx and the upper part of the trachea on both sides. It is divided into two lobes, left and right, connected by an isthmus in the middle, in the shape of “H” or “butterfly”. Function: The thyroid gland is the largest endocrine gland in the body. It mainly secretes thyroid hormones: T3 and T4, which are involved in the metabolism of three major substances, energy and vitamins, and play an important role in the growth and development of the human body and the normal functioning of various systems. It is regulated by TSH secreted by the pituitary gland.