How do a recombinant human thyrotropin Thyrogen scan and treatment work?
A Thyrogen scan is performed by subcutaneously administering a synthetic version of TSH on two consecutive days and then performing the radioiodine scan to detect thyroid tissue. Usually, patients stop taking thyroid medications to ensure that the TSH is maximally stimulating any residual thyroid tissue so that it can be detected on the scan. By giving the patient TSH, a similar physiologic state is obtained. The scans have similar quality to those obtained when a person is put into a more natural low thyroid hormone state by withdrawing the hormone. Similarly, 131 I treatment can be performed after two days of thyrogen injections. Studies have shown that 131 I therapy is similar in those patients receiving Thyrogen and in those who undergo thyroid hormone withdrawal.