The Food and Drug Administration (FDA) has approved recombinant human TSH (rhTSH) for both diagnostic testing and for therapy. Recombinant TSH is used for diagnostic testing when evaluating for recurrence of thyroid cancer. It is also used therapeutically to destroy the residual normal thyroid tissue left after thyroid surgery as well as to help destroy any residual thyroid cancer following such surgery. Diagnostic testing with use of rhTSH is performed in an outpatient setting over five days:
- Day 1 -- Blood draw for thyroglobulin followed by Thyrogen injection.
- Day 2 -- Second Thyrogen injection.
- Day 3 -- The patient may undergo a PET/CT scan (without iodine contrast material) and/or receive a tracer dose of radioactive iodine for a nuclear medicine whole body scan.
- Day 5 -- More blood drawn for thyroglobulin to see if there is a change after stimulation by rhTSH. If radioactive iodine was given, a total body scan is performed to see what tissues take up the radioactive iodine. This test is used diagnostically to see if there is any residual thyroid tissue, and to localize the tissue.