Diagnostic accuracy of 131I scanning with recombinant human thyrotropin versus thyroid hormone withdrawal in a patient with metastatic thyroid carcinoma and hypopituitarism.

The diagnostic and therapeutic use of radioactive iodine in patients with thyroid cancer requires a sufficient serum concentration of thyrotropin (TSH) for efficient thyroid tissue uptake of radioiodine. Recombinant human TSH (rhTSH) is a promising new agent, which appears to facilitate radioiodine scanning with similar efficacy to thyroid hormone withdrawal without the immunologic side-effects of bovine TSH (bTSH) administration. Patients with thyroid cancer and concomitant secondary hypothyroidism are particularly difficult to treat because of their inability to elevate endogenous TSH and the limitations of bTSH administration. We describe a patient with metastatic thyroid carcinoma and secondary hypothyroidism with metastases visible only after administration of rhTSH previously unappreciated on thyroid hormone withdrawal scans. This patient exemplifies the usefulness of rhTSH administration before radioactive iodine for this group of patients.