For a radioactive uptake test, a small amount of radioactively labeled iodine (I-123) or technetium is administered into your bloodstream via an IV. The iodine or technetium is taken up by the thyroid gland cells, where it is stored. You can see this on the computer using a series of photos (a scintigram). These photos show to what extent the thyroid gland takes up the labeled iodine or technetium. With Graves' disease, for example, the uptake of iodine is increased in the entire thyroid gland. If you have a nodule, such as a toxic adenoma, the uptake of the iodine is increased locally. The nodule takes up a lot of iodine, but the rest of the thyroid gland does not. The amount of radioactive substance used is very minimal; it has no effect of your body. You automatically excrete the radioactive substance back out It is therefore extra important to wash your hands thoroughly after using the toilet when you have had this test. A staff member from the Nuclear Medicine Department can provide you with more detailed information. Purpose: to make the amount of functioning thyroid gland tissue visible, whether it is too much or too little.