The thyroid is a small (butterfly-shaped) gland. It is located at the lower part of the neck. Its function is to secrete hormones. The thyroid gland is regulated by control centres in the brain - hypothalamus and pituitary gland. The hypothalamus in our brain releases a thyrotropin-releasing hormone or (TRH). The release of thyrotropin-releasing hormone tells the pituitary gland to release thyroid-stimulating hormone (TSH). This thyroid-stimulating hormone, circulating in your bloodstream, is what tells the thyroid gland to make thyroid hormones and release them into the bloodstream.
The main hormones that are released by the thyroid gland are triiodothyronine (abbreviated as T3) and thyroxine (abbreviated as T4). These are responsible for delivering energy to the cells of our body and are one of the main hormones to control the body's metabolism.