Blood analyser. View of a Technicon Immuno 1 automatic blood analysis machine. Among other tests, it tests samples of blood for thyroid hormones to check that the thyroid gland is functioning properly. The thyroid gland is located in the front of the neck and produces the metabolism-controlling hormones thyroxine (T4) and tri-iodothyronine (T3). Abnormal levels of these hormones may indicate a thyroid disorder.