Partial withdrawal of levothyroxine to stimulate serum thyroglobulin (TG) in the follow-up of differentiated thyroid carcinoma (DTC)
Francesca Ianni, Carlo Antonio Rota, Salvatore Maria Corsello, Annapina De Rosa, Francesca Gallo, Rosa Maria Paragliola, Francesca Ingraudo, Maria Pia Ricciato, Maria Ludovica Maussier, Massimo Salvatori & Alfredo Pontecorvi
Aim: We compared effectiveness of partial withdrawal of levothyroxine (L-T4) to the use of recombinant human TSH (rhTSH) in preparation for Tg testing. We also evaluated clinical aspects and quality-of-life (QOL) during both regimens.
Materials and methods: Ten consecutive patients, previously treated with total thyroidectomy and radioiodine ablation for DTC, underwent rhTSH protocol and, after 15 days, reduced their L-T4 dose by 50% for 5 weeks. At the fourth week TSH was tested (predictive cut-off >10 μUI/ml), and at the fifth week TSH and Tg were measured (cut-off TSH >25 μUI/ml). Patients who did not reach the last cut-off were asked to continue half-dose protocol and to repeat TSH and Tg dosage at the sixth week.
At baseline and at the end of both rhTSH and half-dose protocols, all patients filled out questionnaires for QOL (SF-36) and symptoms and signs of hypothyroidism (Zulewski score). The study was approved by local ethical committee.
Results: Adequate stimulation of Tg was obtained in all patients after rhTSH. At half-dose protocol, 5/10 patients had TSH >25 μUI/ml at the end of the fifth week and 2/10 attained cut-off at the end of the sixth week. One patient left the study, another patient had limited compliance because of depression, and the last one completely withdrew L-T4 to receive radioiodine treatment because of high stimulated-Tg levels although not attaining TSH cut-off.
Tg levels were slightly more sensitive in the partial withdrawal scheme than in the use of rhTSH, but without any statistically significant difference. During the partial withdrawal period 5/7 patients reported no disease-specific morbidity, while 2/7 had just minimal discomfort. On the SF-36 health survey no statistically significant differences were found.
Conclusion: Partial L-T4 withdrawal seems to be an effective, simple, economical and well-tolerated procedure for Tg stimulation during follow-up for DTC.