Endocrine Abstracts (2006) 11 P905

Pretreatment with rhTSH allows effective 131I therapy in patients with multinodular toxic goiter and low radioiodine uptake

M Gietka-Czernel, H Jastrzebska, W Zgliczynski, G Wasniewska, M Wróblewska, K Wernic, B Cybulska & E Karpiska

Dept. of Endocrinology, Medical Center of Postgraduate Education, Warsaw, Poland.

Aim: Estimation of the effectiveness of a single low dose 0.05 mg rhTSH in increasing radioiodine uptake (RAIU) before 131I therapy for multinodular toxic goiter with low initial RAIU.

Patients: 24 patients (21 women, 3 men) with multinodular toxic goiter without prior antithyroid drug therapy. The initial 24 h RAIU was 21.1±8.44%; range, 6–39% and thyroid volume 64.14±22.49 ml; range, 24.8–109 ml.

Methods: A single dose of 0.05 mg rhTSH (Thyrogen, Genzyme) was given im. 24 h later diagnostic activity of 131I was administered and RAIU after 6, 24, 48 and 72 h was estimated. On the 4th day therapeutic dose of 131I adjusted to the increased RAIU was given. Therapeutic dose was calculated to deliver 120–150 μCi 131 I /ml thyroid tissue retained at 24 h.

Results: The significant 3.2-fold increase in 24 h RAIU to 66.9±13.05% after 0.05 mg rhTSH was noted. It allowed to reduce 131I therapeutic dose from the mean 46.6 mCi to 14.3 mCi. Shortly after rhTSH administration (24, 48 h) serum fT3 elevated from 3.08±0.8 pg/ml to peak value 6.02±1.36 pg/ml (P<0.001) and serum fT4 augmented from 19.16±3.59 pmol/l to peak value 29.04±10.11 pmol/l (P<0.001). Clinical signs of thyrotoxicosis exacerbation were mild to moderate. There was 1 case of painful thyroid enlargement without respiratory tract obstruction 24 h after rhTSH administration. Twelve months after 131I therapy 75% of patients were euthyroid, 6.5% hypothyroid and 18.5% still thyrotoxic. There was 45% reduction of thyroid volume.

Conclusions: Administration of a single dose of 0.05 mg rhTSH enhances 3.2-fold RAIU in patients with multinodular toxic goiter. This method enables significant 131I dose reduction but should be carefully undertaken because of the risk of thyrotoxicosis exacerbation and thyroid volume enlargement.

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