The thyroid is a gland at the base of the throat near the trachea (windpipe). It is shaped like a butterfly, with a right lobe and a left lobe. The isthmus, a thin piece of tissue, connects the two lobes. A healthy thyroid is a little larger than a quarter. It usually cannot be felt through the skin.

The parathyroid glands are four pea-sized organs found in the neck near the thyroid. The thyroid and parathyroid glands make hormones.

 The thyroid uses iodine, a mineral found in some foods and in iodized salt, to help make several hormones. Thyroid hormones control the following:

• Heart rate
• Body temperature
• Body metabolism and body weight
• Energy level
• Bowel function

The parathyroid glands make parathyroid hormone which controls the level of calcium in the body. If one or more of the glands is overactive or enlarged it may secrete excess parathyroid hormone which could make your calcium level rise. This could lead to osteoporosis, kidney stones, psychological disturbances or muscle and joint pain.