Recombinant thyrotropin versus thyroid hormone withdrawal in evaluating patients with thyroid carcinoma

Patients with previously treated thyroid carcinoma require lifelong monitoring for recurrent disease. Two diagnostic tests that play a central role in follow-up of these patients--radioiodine whole body scanning and serum thyroglobulin measurement--are most accurate during thyroid-stimulating hormone (TSH) stimulation. Temporary discontinuation of thyroid hormone therapy was previously the sole effective approach for TSH-stimulated testing. However, hormone withdrawal was associated with the morbidity of hypothyroidism and occasional tumor progression. The introduction of recombinant TSH (rTSH)-stimulated testing offers an alternative therapy. Recent clinical trials have shown that the sensitivity of combined rTSH-stimulated radioiodine scanning and serum thyroglobulin measurement has equivalent sensitivity to testing after thyroid hormone withdrawal. Furthermore, measurement of the rTSH-stimulated thyroglobulin concentration is a more sensitive way to detect residual thyroid cancer or normal tissue than thyroglobulin measurement on thyroid hormone therapy alone. The results of these trials are reviewed and strategies for implementing rTSH-mediated testing are presented.