The thyroid is a butterfly-shaped endocrine (hormone secreting) gland in the neck that is found on both sides of the trachea (windpipe).The thyroid secretes three important hormones—thyroxin (T4), triiodothyronine (T3), and calcitonin. T3 and T4 are the thyroid hormones responsible for our overall metabolism and affect almost every cell in our bodies. Calcitonin helps regulate calcium stores in the body and also directs our bone-building process. Iodine is essential to form both T3 and T4. It is one of the most important glands organizing many biochemical functions linked with each other and controlling normal function in our body.