The thyroid is a butterfly-shaped gland in the front of your neck. According to the American College of Cardiology, the thyroid is known to control your metabolism, which is how your body turns food into energy. It also affects your heart, muscles, bones, and cholesterol. The thyroid gland works by using iodine from food to make homones. The pituitary gland, which is in the brain, helps control the thyroid gland. It releases thyroid-stimulating hormones. If the thyroid does not produce enough hormones, it is called hypothyroidism. If the gland produces too many hormones, it is called hyperthyroidism.