The thyroid gland is the biggest gland in the neck. It is situated in the front of the neck, just below your Adam’s apple, on either side of the neck, and partly wraps around the trachea (wind pipe). 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. The thyroid gland receives much of its instruction from the pituitary gland, a small gland located at the base of brain. The pituitary gland secretes Thyroid Stimulating Hormone (TSH). TSH, as its name implies, stimulates the thyroid gland to start producing thyroid hormone. When the thyroid gland starts to slow down or become underactive, it doesn’t produce as much thyroid hormone. When the pituitary senses the thyroid hormone levels are too low, the pituitary produces more TSH as part of a chemical messenger sending a message to the thyroid gland to ask for more thyroid hormone production. Understand that TSH is not an active hormone, it’s a chemical messenger. That’s all. We see TSH levels rise to abnormal levels as we see thyroid hormone levels fall as part of a negative feedback loop. TSH blood levels are commonly measured as a way to screen for thyroid abnormalities. The normal range for most labs is 0.5 – 5.5. The higher the number, the greater the indication of an underactive thyroid. At Chadds Ford Wellness, we prefer to see people in the “optimum” range, under 2.0The main hormone produced by the thyroid gland is T4, also known as levothyroxine. It is a molecule that contains 4 iodine units (hence the “T4”). The T4 gets secreted by the thyroid gland and enters the blood stream. Once it reaches the body, T4 gets converted to T3 (tri-iodothyronine) by cleaving off 1 iodine unit. (A small amount of T3 is also produced directly in the body.) T3 is 4-5 times more active or powerful than T4 and is the real, active thyroid hormone that has its action on all of our cells in our body. If the thyroid gland is underactive (hypothyroidism), insufficient amounts of T4 are produced, resulting in too little T3. On the other hand, your body may also not adequately convert T4 to T3, in spite of adequate T4 levels. This is seen more commonly with a poorly functioning adrenal gland as often seen with patients who are under more than normal physical or psychological stress or even some disease states like anemia.