How the Body Works: The Thyroid Gland

The thyroid gland, situated at the front of the neck and overlying the trachea, consists of two lateral lobes and a connecting isthmus. Thyroid tissues trap iodine circulating in the blood and use it to produce the hormones thyroxine and triiodothyronine. When secreted into the bloodstream, these hormones increase the metabolic rate of all body tissues. The thyroid gland also produces the hormone calcitonin, which helps regulate the calcium content of bones.