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.

Without a functioning thyroid, the body would not be able to break down proteins and it would not be able to process carbohydrates and vitamins. For this reason, problems with this gland can lead to uncontrollable weight gain. For many people, these irregularities can be controlled through medications, as well as a modification of their diet.

However, there is one other controlling factor. The gland cannot produce hormones on its own. It needs the assistance of the pituitary gland, which creates thyroid stimulating hormone (TSH). As a result, a nonfunctional pituitary gland will eventually lead to thyroid-gland-related issues. TSH will either trigger the production of thyroxine or triiodothyronine. If TSH is not present at the right levels, too much or too little of either hormone will be made.