This is a hormone made by the pituitary gland located at the base of the brain. It is released when there is too little thyroid hormone (thyroxine) in the blood. Its job is to stimulate the thyroid gland to release more thyroid hormone. People with hypothyroidism do not make enough thyroid hormone so the pituitary releases more TSH in order to try to increase the amount of thyroid hormone released. Testing for the level of both thyroxine (T4) which is low in people with hypothyroidism, and the level of TSH, which is high in people with hypothyroidism, helps doctors make the diagnosis.