The thyroid gland is an essential part of the endocrine system which works in concert with the brain and nervous system to control vital organ systems. The thyroid is a butterfly shaped organ that sits at the base of the neck which releases hormones that control metabolism, or how the body uses energy. Thyroid hormones regulate essential body functions such as breathing, heart rate, muscle contractions, nervous system actions, menstrual cycle, weight and much more. When thyroid hormones are out of balance there can be symptoms such as hair loss, weight gain or weight loss, dry skin, cold hands/feet/nose, fatigue, and even anxiety symptoms.
The thyroid gland is part of the endocrine system, which is made up of glands that produce, store, and release hormones into the bloodstream to communicate with cells. The thyroid gland uses iodine from the foods you eat to make two main hormones: Triiodothyronine (T3) and Thyroxine (T4). It is important that T3 and T4 levels are neither too high nor too low. Two glands in the brain, the hypothalamus and the pituitary communicate to the thyroid via TSH (Thyroid Stimulating Hormone) to maintain T3 and T4 balance. The hypothalamus produces TSH Releasing Hormone (TRH) that signals the pituitary to tell the thyroid gland to produce more or less of T3 and T4 by either increasing or decreasing the release of TSH. When T3 and T4 levels are low in the blood, the pituitary gland releases more TSH to tell the thyroid gland to produce more thyroid hormones. If T3 and T4 levels are high, the pituitary gland slows down the release of TSH to the thyroid gland to slow production of these hormones. Measuring Free T3 and Free T4 can be much more informative than serum T3 or T4 since the latter are hormones bound in the blood. By measuring unbound or "Free" levels clinicians are able to assess what amount of active hormone is actually making it into the tissues where it has physiological effects.