The thyroid gland is located just below the larynx. The principal hormone secreted by this gland is the thyroxine hormone which regulates the metabolism in the human body, such as maintaining normal blood pressure, heart rate, digestion, muscle tone and reproductive functions. The thyroid gland plays a vital role in the growth of bones and development of the brain and nervous system in children. When the secretion of thyroxin is low, it leads to a condition called cretinism which lowers the rate of metabolism and causes the retardation of growth. Deficiency of thyroxin leads to one more hormonal disorder called hypothyroidism.