The thyroid is an endocrine gland, located in the neck just below the voice box, which produces the hormones that control your metabolism. A healthy metabolism ensures the other organs in your body function well and also ensures a healthy temperature, heart rate, energy level and growth rate. Thyroid hormone production starts with the pituitary gland. If the gland determines your body needs more thyroid hormone, it sends thyroid stimulating hormone (TSH) to the thyroid gland to increase production.

In addition to thyroid glands, there are parathyroid glands, which sit behind the thyroid gland, that control the level of calcium in the bloodstream by making parathyroid hormone (PTH). Healthy calcium levels help muscle and nerves work properly and keep bones strong.