Introduction
The thyroid is a small, butterfly-shaped gland located just below the Adam's apple. This gland plays a very important role in controlling your body's metabolism, that is, the rate at which your body uses energy. It does this by producing thyroid hormones (primarily thyroxine, or T4, and triiodothyronine, or T3), chemicals that travel through your blood to every part of your body. These thyroid hormones tell the cells in your body how fast to use energy and create proteins. The thyroid gland also makes calcitonin, a hormone that helps to regulate calcium levels in the blood by inhibiting the breakdown (reabsorption) of bone and increasing calcium excretion from the kidneys. The thyroid gland is located in the front of the neck, just below the voice box (larynx). It produces chemicals (hormones) that help the body control metabolism. Thyroid hormone is normally produced in response to another hormone released by the pituitary gland.
Hyperthyroidism -- too much thyroid hormone
Hypothyroidism -- too little thyroid hormone
Benign (noncancerous) thyroid disease
Thyroid cancer