The thyroid gland is a butterfly-shaped endocrine gland that is normally located in the lower front of the neck. The job of the thyroid is to secrete hormone, which are secreted into the bloodstream and then carried to every tissue in the body. Thyroid hormones help the body use energy, stay warm and keep the brain, heart, muscles and other organs working properly.
How does the Thyroid gland work?
The main thyroid hormone secreted by the thyroid gland is thyroxine, also called T4 because it contains four iodine atoms. To exert its effects, T4 is converted to triiodothyronine (T3) by the removal of an iodine atom. This occurs mainly in the liver and in certain tissues where T3 acts, such as in the brain. The amount of T4 produced by the thyroid gland is controlled by another hormone, which is made in the pituitary gland located at the base of the brain, called the thyroid stimulating hormone (abbreviated TSH). The amount of TSH that the pituitary gland sends into the bloodstream depends on the amount of T4. If the pituitary gland is in small amounts of T4, then it produces more TSH to tell the thyroid gland to produce more T4. Once the T4 in the bloodstream goes above a certain level, the pituitary TSH production of TSH is turned off. In fact, the thyroid and pituitary gland function in many ways like a heater and a thermostat. When the heater is turned off and becomes cold, the thermostat reads the temperature and the heater turns on. When the heat rises to a proper level, the thermostat senses this and turns off the heater.
Blood tests to measure these hormones are available and widely used. Tests to assess thyroid function include the following:
TSH – measures thyroid stimulating hormone. More accurate measurement of thyroid activity.
T3 dhe T4 – measure different thyroid hormones
Anti TPO – Antithyroid antibody test -mat antibodies (markers in the blood).