Endocrine Abstracts (2009) 20 P123

The outcome of radioiodine therapy in Graves' hyperthyroidism: thyroid size as prognostic factor

Jolanta Kijek1, Jerzy S Tarach2, Maria Kurowska2 & Helena Jankowska1

1Department of Nuclear Medicine, Medical University, Lublin, Poland; 2Department of Endocrinology, Medical University, Lublin, Poland.

Aim: The aim of the study was the evaluation of the relationship between thyroid size and the result of radioactive iodine therapy in patients treated due to Graves’ hyperthyroidism.

Material and methods: The study group included 150 subjects (127 M and 23 F), aged from 20 to 78 years (mean 48.33 years) at the moment of 131I therapy.

In all patients the thyroid technetium-99m scan and determination of the serum levels of fT3, fT4 (FIA ‘Delfia’ method), TSH (IFMA ‘Delfia’method), TSHRAb (radioreceptor method ‘TRAK Assay’) were performed. Iodine uptake was measured at 24-h, 48-h, then half-life has been determined. The thyroid weight was estimated on the basis of thyroid technetium-99m scan. The therapeutic activity of 131I was calculated according to Marinelli’s formula.

After one year follow-up, the thyroid function has been estimated.

Successful therapy was defined as euthyroidism or permanent hypothyroidism.

Results: The thyroid weight in the group of patients before treatment ranged from 54 to 367 g (mean 72.34±47.24 g). After one year, euthyrosis was observed in 47 patients (31.35%), hypothyroidism in 47 parsons (31.35%). In 56 subjects (37.3%) persistent hyperthyroidism have been diagnosed. Among patients with successful therapy, the thyroid mass ranged between 5.4 and 367 g (mean 61.97±45.5 g), but in ineffective therapy group ranged between 8.2 and 196.0 g (89.59±45.36 g).

The difference of thyroid mass was statistically significant (P=0.0004).

Conclusions: The obtained results confirm, that 131I therapy is effective method of hyperthyroidism treatment, but patients of the ineffective therapy group presented larger goiter.

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