Recombinant human thyrotropin (rhTSH) in the management of differentiated thyroid cancer

Recombinant human thyrotropin (rhTSH) has been evaluated in 38 patients with differentiated thyroid cancer. The patients had all been treated previously by operation and 31 had received radioiodine 131I. The patients continued to take thyroid hormone and changed to a low iodine diet for 14 days before and throughout the week of testing. The rhTSH was injected intramuscularly on two consecutive days, 74 MBq 131I was administered on the next day and scintigraphy completed 48 h after that. TSH was measured before administration of 131I, and thyroglobulin after the scan. All patients preferred this method to withdrawal of thyroid hormone, but 45% had mild symptoms including headache and nausea. The average TSH was 127 mU x l(-1), and was inversely related to the weight of the patients. Thirty-four had negative scans with a mean uptake of 0.06%. Thyroglobulin values above 10 ng x ml(-1) were found in seven patients, of whom four had similar findings when scanned after withdrawal of thyroid hormone. Of four with positive scans, two had undetectable thyroglobulin. The rate of clearance of 131I was compared in patients studied at 72 h who were hypothyroid and at 48 h in euthyroid patients given rhTSH and was found to be longer in the latter. We conclude that rhTSH can be used to stimulate thyroid tissue to trap 131I and secrete thyroglobulin. Both scan and thyroglobulin should be obtained. The method is well tolerated.