Many clinicians care for patients who have been treated for differentiated thyroid cancer. Recombinant thyrotropin, which stimulates iodine uptake in thyroid tissue, is a safe and effective diagnostic agent for those patients who require radioiodine scanning for routine follow-up. The combination of a whole body radioiodine scan and a serum thyroglobulin measurement can identify virtually all patients with distant metastatic disease. A serum thyroglobulin >2 ng/mL and/or a positive whole body scan after recombinant thyrotropin stimulation suggest residual thyroid tissue or neoplastic disease. The use of recombinant thyrotropin has fewer adverse effects than does the alternative, which is withdrawal of thyroid hormone replacement, although nausea and headache have been reported. However, recombinant thyrotropin is expensive.