TY - JOUR T1 - Dosimetry of Radioiodine Therapy in Patients with Nodular Goiter After Pretreatment with a Single, Low Dose of Recombinant Human Thyroid-Stimulating Hormone JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 626 LP - 633 VL - 45 IS - 4 AU - Willy-Anne Nieuwlaat AU - Ad R. Hermus AU - H. Alec Ross AU - Wilhelmina C. Buijs AU - Michela A. Edelbroek AU - Jo W. Bus AU - Frans H. Corstens AU - Dyde A. Huysmans Y1 - 2004/04/01 UR - http://jnm.snmjournals.org/content/45/4/626.abstract N2 - A single, low dose of recombinant human thyroid-stimulating hormone (rhTSH) doubles 24-h RAIU and causes a more homogeneous distribution of radioiodine on thyroid scintigrams of patients with nodular goiter. Pretreatment with rhTSH allows the therapeutic dose of 131I to be reduced by 50%–60% without compromising the result of thyroid volume reduction. The present study focused on the dosimetric aspects of therapy with a reduced dose of 131I after pretreatment with rhTSH in patients with nodular goiter. Methods: Thirty-six patients were treated with 131I to reduce thyroid volume. Nine patients were pretreated with a single dose of 0.01 mg of rhTSH, and 9 patients, with 0.03 mg of rhTSH. Two control groups of 9 patients, matched for thyroid weight and 24-h radioactive iodide uptake, were not pretreated with rhTSH. The therapeutic dose of 131I was aimed at being sufficient to result in retention of 3.7 MBq of 131I per gram of thyroid tissue at 24 h. Thyroid radioactivity after 131I administration was measured every 24 h for 3 d and on days 7, 10, 14, 21, and 28. A model of iodine biokinetics was used to estimate absorbed doses in organs. Protein-bound 131I activity was measured at 1, 2, 3, 7, and 10 d and at 2, 3, and 4 wk after 131I therapy. Results: The administered activities were 1.5 times lower in the 0.01-mg rhTSH group and 1.9 times lower in the 0.03-mg rhTSH group than in the control groups. The absorbed dose in the thyroid was similar in the rhTSH-pretreated groups and in the control groups. In the organs of excretion (bladder) and uptake (stomach) of inorganic iodide, the absorbed doses were 2- to 3-fold lower in the pretreated groups than in the control groups. The effective dose equivalent outside the thyroid was considerably lower in the rhTSH-pretreated groups than in their respective control groups (1.6-fold in the 0.01-mg rhTSH group and 2.3-fold in the 0.03-mg rhTSH group). The time course of protein-bound 131I activity in serum and the cumulated protein-bound 131I activity in serum did not differ significantly between rhTSH-pretreated and control groups. Conclusion: 131I therapy after pretreatment with a single, low dose of rhTSH, with the dose reduced according to the rhTSH-induced increase in 24-h radioactive iodide uptake, caused lower radiation-absorbed doses in extrathyroidal organs and tissues, especially bladder and stomach, and no significant increase in the release of 131I-labeled thyroid hormones into the circulation of patients with nodular goiter. Thus, this mode of therapy can be recommended, especially when the dose of radioiodine to be administered without rhTSH pretreatment is high. ER -