Thyroid hormones are released from the gland

The thyroid gland is the biggest gland in the neck. It is situated in the anterior (front) neck below the skin and muscle layers. The thyroid gland takes the shape of a butterfly with the two wings being represented by the left and right thyroid lobes which wrap around the trachea. The sole function of the thyroid is to make thyroid hormone. This hormone has an effect on nearly all tissues of the body where it increases cellular activity. The function of the thyroid therefore is to regulate the body's metabolism.

Thyroid hormones are released from the gland and travel through the bloodstream to your body's cells. They help control the growth and the structure of bones, sexual development (puberty), and many other body functions. By helping your cells convert oxygen and calories into the energy they need to work properly, these hormones are important in determining if your body will mature as it should. Thyroid hormones also directly affect how most of your organs function. So if your thyroid isn't operating properly, you can have problems in lots of other parts of your body.

There are actually two thyroid hormones, thyroxine (T4, or tetraiodothyronine) and triiodothyronine (T3). Their structure is identical, except that thyroxine has four iodine atoms and triiodothyronine has three. Under normal conditions, the thyroid produces more thyroxine than triiodothyronine. The raw materials needed to form thyroid hormone are iodine and the amino acid tyrosine, both of which are normally found in a person’s diet.