The thyroid is a butterfly-shaped gland that lies in front of the
windpipe, also known as the trachea, and just below the voice box, also called
the larynx. This gland makes hormones that regulate the way the body uses
The thyroid gland uses iodine from food to make two thyroid
hormones: thyroxine (T4) and triiodothyronine (T3). The thyroid gland stores
these hormones and releases them into the bloodstream as they are
If the thyroid gland does not produce enough hormones, it is
called hypothyroidism. If the gland produces too many hormones, it is called
hyperthyroidism. Problems with the thyroid gland can affect many body systems.
Changes in weight, heartbeat, body temperature, digestion, and muscle function
are common. Both hypothyroidism and hyperthyroidism can be treated, usually
with medicine and sometimes with surgery.