Can the basal serum thyroglobulin level be used to predict the recombinant human TSH-stimulated thyroglobulin level in differentiated patients with thyroid cancer?

This study investigated the correlation between basal thyroglobulin (Tg) and recombinant human thyroid-stimulating hormone (rhTSH)-stimulated Tg in differentiated patients with thyroid cancer, and sought to determine whether the basal Tg level predicts the rhTSH-stimulated Tg level. We retrospectively enrolled 177 patients with papillary thyroid cancer (mean age = 44 years; 50 males, 127 females) who received rhTSH before radioiodine therapy (RIT). Serum Tg levels were measured 7 days before the 1st rhTSH injection (basal Tg) and on the days of RIT (rhTSH-stimulated Tg). Patients were divided into 3 groups according to rhTSH-stimulated Tg cut-off levels of 2, 5, and 10 ng/mL. The correlation between basal Tg and rhTSH-stimulated Tg levels was assessed, and whether basal Tg was useful in predicting the rhTSH-stimulated Tg level was determined. A significant positive correlation was observed between basal and rhTSH-stimulated Tg levels (|rho| = 0.48, P < .0001). The basal Tg level had significant diagnostic ability in predicting an rhTSH-stimulated Tg level of 2 ng/mL or higher, and the optimal basal Tg level for this prediction was 0.3 ng/mL (AUC = 0.77, P < .0001). A basal Tg level of 0.5 ng/mL was optimal for predicting rhTSH-stimulated Tg levels of 5 ng/mL or higher (AUC = 0.81, P < .0001), and of 10 ng/mL or higher (AUC = 0.82, P = .0171). The basal Tg level was significantly correlated with the rhTSH-stimulated Tg level. If the basal Tg level is >0.3 or 0.5 ng/mL, then the rhTSH-stimulated Tg level can be expected to be sufficiently high to necessitate clinical examination.