The Thyroid Gland
The thyroid is a butterfly shaped gland that is part of the endocrine system. You can find it just below your Adams apple on the front of your neck.
The endocrine system is a sophisticated network of glands that produces and secretes hormones that regulate our cells and organs. These hormones are critical for the operation of our bodies. The major glands of the endocrine system are the hypothalamus, pituitary, thyroid, parathyroid, adrenals, pineal body, and the reproductive glands (ovaries & testes).
The primary role of the thyroid in adults is to produce and secret hormones into your blood stream that regulate the body's metabolism. Metabolism is a term that is used to describe all chemical reactions involved in maintaining the living state of the cells and the body.
The two main hormones the thyroid produces are Triiodothyronine (T3) and Thyroxine (T4). If you have too much or too little of these hormones, your metabolism either speeds up or slows down, in either case throwing you and your body off balance and impacting everything from blood pressure and heart rate, to digestion and brain function.
The quantity of hormones produced by the thyroid is regulated by the pituitary gland, which in turn is regulated by the hypothalamus.
If your body needs more thyroid hormones the signal is sent from the hypothalamus to the pituitary gland in the form of a "releasing hormone" (TRH). This stimulates the pituitary gland to secrete a "stimulating hormone" (TSH) into the bloodstream which signals to the thyroid to secrete its hormones. If your body has enough thyroid hormones then the process is put on hold until such time they are required. It works very much like the thermostat in your house: checking levels in your blood regularly and switching on or off as needed to maintain the perfect balance and a stable level of hormones.