The thyroid gland is the largest endocrine gland in the body and is divided into two lobes, located in the upper part of the trachea in the lower larynx and in the front of the esophagus. Its main functions are to promote metabolism, promote human growth and development, promote the growth and development of the brain and genitals, and increase the excitability of the central nervous system. Common thyroid disorders include: hyperthyroidism, hypothyroidism, Hashimoto’s thyroiditis, and thyroid tumors.