What is the thyroid gland and what does it do?

The thyroid gland is part of the endocrine system. It is located in the lower front part of the neck, just below the Adam's apple and above the top edge of the breastbone. It wraps around portions of the larynx (voice box) and trachea (windpipe) that pass through the lower front part of the neck.

The thyroid produces hormones that enter the bloodstream and travel throughout the body. These hormones stimulate tissues and organs throughout the body to regulate body temperature, the metabolism, chemical balance, and reproductive functions. The thyroid also helps to maintain normal functioning of the cardiovascular system and the central nervous system.

The thyroid itself is regulated by a hormone produced by the pituitary gland called TSH. In response to signals provided by TSH, the thyroid hormone takes up iodine, which is essential for the synthesis of thyroid hormones, and uses it to produce two forms of thyroid hormone called T3 and T4, which are released into the bloodstream. It is important to note that the thyroid is unable to distinguish between radioactive iodine and nonradioactive iodine.