The thyroid gland covers the windpipe from three sides. Two hormones of the thyroid gland, T3 (thyroxine) and T4 (triiodothyronine), help the body to produce and regulate the hormones adrenaline (also called epinephrine) and dopamine. Hormones are chemical substances that help control certain cells and organs. Adrenaline and dopamine are active in many physical and emotional responses, including fear, excitement, and pleasure. Other hormones from this gland also help regulate metabolism, which is the process by which calories and oxygen are converted into energy.