Treatment of MNG with RAI

Recombinant human thyrotropin-stimulated radioiodine therapy of nodular goiter allows major reduction of the radiation burden with retained efficacy.

Fast S , Hegedüs L , Grupe P , Nielsen VE , Bluhme C , Bastholt L , Bonnema SJ

J Clin Endocrinol Metab. 2010 Aug;95(8):3719-25. Epub 2010 Jun 2.

Stimulation with recombinant human TSH (rhTSH) before radioiodine (131I) therapy augments goiter volume reduction (GVR). Observations indicate that rhTSH has a preconditioning effect beyond increasing thyroid (131)I uptake. We test the hypothesis that an equivalent GVR might be obtained by an absorbed thyroid dose well below what has been used previously.

In a double-blinded setup, 90 patients (78 women; median age, 52 yr; range, 22-83) with a nontoxic nodular goiter (median size, 63 ml; range, 25-379 ml) were randomized to either 0.1 mg rhTSH (n=60) followed by a thyroid dose of 50 Gy or placebo followed by 100 Gy (n=30).

At 12 months, the mean relative GVR in the placebo and the rhTSH group was identical (35+/-3%; P=0.81). The median administered 131I-activity was 170 MBq (45-1269) in the rhTSH group and 559 MBq (245-3530) in the placebo group (70% reduction, P<0.0001). According to the official radiation regulation, hospitalization was required in 14 patients in the placebo group vs. one patient in the rhTSH group (P<0.0001). In both groups, goiter-related symptoms were effectively relieved in the majority of patients. The prevalence of myxedema (10%) did not differ among groups.

Comment

This is the first study to demonstrate that rhTSH not only increases the thyroid 131I uptake during treatment of MNG, but potentiates the effect of 131I-therapy, allowing a major reduction of the 131I-activity without compromising efficacy. This approach is attractive in terms of minimizing post-therapeutic restrictions and in reducing the potential risk of radiation-induced malignancy.

Comment

131-I therapy to reduce the bulk of MNG gradually becomes more common in the USA, and this report shows that the dosage can be reduced by using rhTSH to satimulate thyroid uptake of the administered RAI. Fears of inducing thyroid malignancy are always appropriate, but in fact that outcome is extremely unlikely given the experience treating patients of this age. Ho