The influence of non-radioactive iodine (127I) on the outcome of radioiodine (131I) therapy in patients with Graves’ disease and toxic nodular goitre
BACKGROUND: The aim of the study was to achieve an effective
target dose in the thyroid by increasing the effective half-life
(Teff) of 131I by use of iodide (127I) two days after 131I therapy in
patients with hyperthyroidism with low Teff.
MATERIAL AND METHODS: The study was carried out in two
groups. Group A — 41 patients, and Group B — 14 patients,
all the patients were with hyperthyroidism with Teff less than 3
days qualified for 131I therapy. Only group A patients received
600 μg of iodide a day for 3 days, two days after 131I therapy.
Radioiodine uptake (RAIU) after 24 and 48 hours, thyroid
scintiscan and ultrasonography were done before and after 12
months of 131I therapy.
RESULTS: In group A a significant increase was seen in the Teff
(5 days on average) resulting in an increase in the energy target
dose by 28% and 37%, in patients with Graves’ disease (GD) and
toxic nodular goitre (TNG), respectively. After one year of therapy 50% of GD and 93% of TNG patients achieved euthyroidism;
28% of GD and 3% of TNG patients were in hypothyroidism. In
Group B, all the patients had radioiodine treatment failure and
received a second therapeutic dose of 131I.
CONCLUSIONS: Administration of 127I after 131I treatment can
lead to an increase in its effective half-life. This will also increase
the absorbed energy dose in thyroid tissue, thereby improving
therapeutic outcome without administration of a higher or
second dose of 131I. This may minimize whole-body exposure
to radiation and reduces the cost of treatment.
Nuclear Med Rev 2011; 14, 1: 9–1