Thyroid Research Thyroid Research Archive Nodular Goiter

Low radioiodine doses reduce the size of multinodular goiters when iodine uptake is stimulated by thyrotropin

(November 2003)

The background of the study. Radioactive iodine (I-131) therapy decreases goiter size in patients with a multinodular goiter, but high doses are needed because thyroid uptake of I-131 is not high. In this study the ability of injections of thyrotropin (TSH) to stimulate I-131 uptake, and therefore allow the use of lower doses of I-131 to reduce goiter size, was tested.

How the study was done. Twenty-two patients (average age, 60 years) with a nontoxic multinodular goiter were studied. Thyroid I-131 uptake was measured 24 hours after the oral administration of I-131. Then, the patients were given a single intramuscular injection of 0.01 or 0.03 mg of human TSH, followed a second measurement of 24-hour I-131 uptake. Two or more weeks later the patients were given the same dose of TSH, and 24 hours later they were given a therapeutic dose of I-131. The patients were reexamined and had measurements of thyroid volume by ultrasonography for one year.

The results of the study. The higher dose of TSH stimulated 24-hour thyroid I-131 uptake more than did the lower dose, allowing a greater reduction in the dose of I-131 needed to deliver the same radiation dose to the thyroid. The patients given the low dose of TSH were treated with an average of 39 mCi (1443 MBq) of I-131; their thyroid volume decreased from 143 ml before treatment to 91 ml one year later, a decrease of 35 percent. The patients given the high dose of TSH were treated with 23 mCi (851 MBq) of I-131; their thyroid volume decreased from 103 ml before treatment to 62 ml one year later (a 41 percent decrease).

The conclusions of the study. Patients with a multinodular goiter who are given TSH to increase I-131 uptake can be treated effectively with relatively low doses of I-131 to decrease goiter size.

The original article. Nieuwlaat WA, Huysmans DA, van den Bosch HC, Sweep CG, Ross HA, Corstens FH, Hermus AR. Pretreatment with a single, low dose of recombinant human thyrotropin allows dose reduction of radioiodine therapy in patients with nodular goiter. J Clin Endocrinol Metab 2003;88:3121-9.