Clinical value of different responses of serum thyroglobulin to recombinant human thyrotropin in the follow-up of patients with differentiated thyroid carcinoma

In the present study we examined the clinical value of a differential response of thyroglobulin (Tg) concentration after recombinant human thyrotropin (rhTSH) stimulation (rhTSH Tg testing) and its correlation with 131I uptake and whole-body scanning (rhTSH-WBS) in 104 patients who had previously undergone near-total thyroidectomy and 131I ablation for differentiated thyroid carcinoma (DTC). rhTSH Tg testing was considered negative for rhTSH-Tg less than 0.9 ng/mL, low positive for rhTSH-Tg of 1-5 ng/mL and high positive for rhTSH-Tg greater than 5 ng/mL. rhTSH Tg testing was negative in 70 patients, 1 of whom had a lymph-node metastasis, but no 131I uptake. Seven patients had low positive rhTSH Tg testing and no 131I uptake, but 2 of these patients had cervical lymph node metastases. Twenty-seven patients had high positive rhTSH Tg testing and 131I uptake was detected in lung, bone, or mediastinum in 11. Imaging techniques (computed tomography [CT], magnetic resonance imaging [MRI], fluorine-18 2-fluoro-2-deoxy-D-glucose-positron emission tomography [FDG-PET]) documented metastatic disease in 22. In conclusion, our results suggest that any rise in rhTSH-Tg, even at low level, should raise the suspicion of persistent or recurrent DTC. Patients with rhTSH-Tg at high level should be carefully evaluated, because DTC persistence is highly probable. TSH-WBS provides little adjunctive information.