Radioiodine ablation of thyroid remnants in patients with differentiated thyroid carcinoma (DTC) following administration of rhTSH - a comparison with L-thyroxine withdrawal.

INTRODUCTION: A group of differentiated thyroid carcinoma (DTC) patients receiving post thyroidectomy rhTSH-aided radioiodine treatment (group I) was compared with patients treated with ¹³¹I following endogenous stimulation of TSH (group II) after L-thyroxine withdrawal.

MATERIAL AND METHODS: Group I consisted of 66 patients of mean age 51.7 ± 16.2 years (58 females and 8 males). Group II included 76 patients of mean age 54.8 ± 14.7 years (67 females and 9 males). All patients underwent total thyroidectomy and central lymph node dissection and additionally lateral lymph node excision, if required. Prior to radioiodine treatment thyroid volume (VT) and 24-hour ¹³¹I uptake were evaluated. TSH and Tg concentrations were measured prior to and after endogenous and exogenous stimulation of TSH. Whole-body post-therapeutic scintigraphy was evaluated. Basic statistics, W Shapiro-Wilk, Wilcoxon, and U Mann-Whitney tests were applied.

RESULTS: Median values of VT and of 24-hr ¹³¹I uptake in groups I and II were not significantly different. The differences between median values of serum TSH concentration after stimulation in groups I and II were statistically significant (p < 0.05), respective medians being 100.0 μU/mL (IQR = 107.3) and 78.8 μU/mL (IQR = 47.7). Median values of serum Tg concentrations in groups I and II following TSH stimulation prior to radioiodine treatment were 2.6 ng/ml (IQR = 8.4) and 4.9 ng/mL (IQR = 12.6), respectively, the difference not being statistically significant. Following rhTSH treatment no adverse effects were observed compared to LT4 withdrawal.

CONCLUSIONS: rhTSH may be safely used for ¹³¹I thyroid remnant ablation in low-risk DTC patients.