There are two types of thyroid nuclear medicine tests. Both assess the health of your thyroid, a gland in your neck. The first type, a thyroid scan, produces a picture of the gland. It can spot lumps or inflammation, or to investigate the cause of an overactive thyroid. The second type, a radioactive iodine uptake test, is performed to see if your thyroid is functioning normally and to determine why thyroid hormone levels may be elevated. For both types of test, a small amount of a weakly radioactive substance, known as a radionuclide, is either injected into a vein or given to you as a pill.