Abnormality of thyroid physiology Positive perchlorate discharge test 2017-05-14T16:04:53Z Individuals with Pendred syndrome may show a positive perchlorate discharge test. An abnormal result of the perchlorate discharge test. In this test, first radioactive iodine is administered, sufficient time is allowed to pass so that the radioactive iodine is captured by the thyroid,and then, perchlorate is administered orally. The perchlorate displaces non-organified iodide from the thyroid. The perchlorate discharge test is considered positive (abnormal) if there is an abnormally rapid loss of radioactive iodine from the thyroid.