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 I-131 uptake and whole body scanning (rhTSH-WBS) in 104 patients who had previously undergone near total thyroldectomy and I-131 ablation for differentiated thyroid carcinoma (DTC). RhTSH Tg testing was considered negative for rhTSH-Tg < 0.9 ng/mL, low positive for rhTSH-Tg of 1-5 ng/mL and high positive for rhTSH-Tg > 5 ng/mL. RhTSH Tg testing was negative in 70 patients, one of whom had a lymph-node metastasis, but no I-131 uptake. Seven patients had low positive rhTSH Tg testing and no I-131 uptake, but two of these patients had cervical lymph-node metastases. Twenty-seven patients had high positive rhTSH Tg testing and I-131 Uptake was detected in lung, bone, or mediastinum in 11. Imaging techniques (CT, MRI, 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, since DTC persistence is highly probable. TSH-WBS provides little adjunctive information.