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.
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