Recombinant Human Thyrotropin Markedly Changes the131I Kinetics during131I Therapy of Patients with Nodular Goiter: An Evaluation by a Randomized Double-Blinded Trial
Journal of Clinical Endocrinology and Metabolism
The present study compares, in a randomized double-blinded design, the expected and the actual absorbed thyroid radioactive dose in response to 0.3 mg recombinant human thyrotropin (rhTSH) (n=35) or placebo (n=28) given 24 hours before 131 I-therapy in patients with nodular goiter (median volume: 69 ml, range 20-440 ml). The 131 I activity calculation was based on thyroid 131 I-uptake (RAIU) at 24h and 96h after a tracer dose of 0.5 MBq 131 I. After 131 I-therapy, 24h and 96h RAIU were repeated
... RAIU were repeated allowing a more exact assessment of the actual absorbed thyroid dose. The median 131 I activity was 617 MBq and 632 MBq respectively, in the rhTSH and the placebo group. At baseline, the 24h, the 96h RAIU, and the expected thyroid dose were 32.8±9.1%, 32.1±8.2%, and 96.3±16.3 Gy respectively, in the rhTSH group, and 35.7±11.8%, 35.2±11.3%, and 94.1±18.5 Gy respectively, in the placebo group (p=NS between groups). After 131 I therapy, the 24h, the 96h RAIU, and the actual absorbed thyroid dose were 46.9±11.7%, 45.0±12.1% and 136.7±47.9 Gy respectively, in the rhTSH group, and 33.0±11.4%, 31.0±11.3% and 76.9±27.5 Gy respectively, in the placebo group (p<0.001 between groups). Comparing the expected with the actual absorbed thyroid dose, this corresponds to a mean increase of 36.4% [95% CI: 21.3-53.4] in the rhTSH group and a decrease of 21.5% [95% CI: ÷33.9-÷6.6] in the placebo group (p<0.001), equivalent to an increase of 73.8% in the absorbed thyroid dose in the rhTSH-treated group. We have thus for the first time shown that stimulation with rhTSH before 131 I-therapy not only hinders the decrease in the thyroid RAIU observed with conventional 131 I-therapy, but in fact significantly enhances the absorbed thyroid dose. Whether this also leads to a significant increase in goiter size reduction needs further study.