The Thyroid Gland controls your bodys functions by making several hormones, incling T4, which is converted to T3.  If you get enough iodine in your diet, your thyoroid cannot proced enough T3 and T4.  The amounts of T3 and T4 released into the bloodstreem:

 Regulates the body's ability to turn food into energy
 Affects rates of tissue growth
 Affect the funtion of organ systems throughout the body