The thyroid is a butterfly-shaped gland that lies in front of the windpipe (trachea), just below the voice box (larynx). The thyroid gland uses iodine from food to make two thyroid hormones that regulate the way the body uses energy.

The parathyroid glands are four tiny glands located behind the thyroid gland. The parathyroid glands produce a substance (parathyroid hormone) that helps control the amount of calcium in the blood.