Long-term follow-up studies on Iodine-131 treatment of hyperthyroid graves’ disease based on the measurement of thyroid volume by ultrasonography

Abstract

In the present series of studies, the long-term (four year) effect of 80 Gy of 131I treatment was evaluated in patients with hyperthyroid Graves' disease whose thyroid volumes have been accurately estimated with a high resolution ultrasound scanner. One year after 131I treatment, 23.1% (3 out of 13 patients) remained hyperthyroid, 69.2% (9 out of 13) became euthyroid, and 7.7% (1 out of 13) were in a hypothyroid state. Since three patients in a hyperthyroid state one year after treatment were subsequently treated with either antithyroid drugs or additional 131I treatment, the remaining ten patients (9 euthyroid and 1 hypothyroid patients) have been followed up for three more years. Two patients developed a hypothyroid state three years after treatment and one patient four years after treatment. Overall, 60% (6 out of 10 patients) were in a euthyroid state and 40% (4 out of 10) in a hypothyroid state, four years after 80 Gy 131I treatment. There was no significant difference between eu- and hypothyroid groups in the sex ratio, age, radiation dose, therapeutic dose, thyroid gland volume, 24-hr 131I uptake, the effective half-life of 131I in the thyroid or the duration of hyperthyroidism. In our preliminary studies, the incidence of late hypothyroidism in our 131I treatment is similar to those previously reported. These suggest that uncertain factor(s), such as inhomogeneity of iodine distribution in the thyroid, unequal sensitivity of the thyroid cells to the radiation, and/or persistent destructive effects of the autoimmune process may influence the long-term effect of 131I treatment of Graves' disease.

Ultrasonographic Thyroid Volume as a Reliable Prognostic Index of Radioiodine-131 Treatment Outcome in Graves’ Disease Hyperthyroidism

“…In Italy, a country with a low iodine intake, Chiovato et al [19] demonstrated a significant reduction in thyroid volume one year after 131 I treatment, but this not was investigated afterwards. The lack of influence of pretreatment thyroid volume on the outcome of 131 I treatment has also been reported by other study [20]. Table 2 Thyroid volume (mean SD) and its reduction after 131 I or spontaneous remission (expressed in ml and percentage of reduction respectively)…”

Effect of thyroid volume on radioiodine therapy outcome in hyperthyroid cats

“…22 Therefore, it is reasonable to consider an effect of thyroid volume on therapy outcomes. Most studies in humans have not found any relationship between thyroid gland size and a hypothyroid outcome, [23][24][25] although one study reported that smaller goitres were a risk factor for developing hypothyroidism. 26 Thyroid size estimation by palpation, as a scoring factor Effect of thyroid volume on radioiodine therapy outcome in hyperthyroid cats Veerle Volckaert 1 , Eva Vandermeulen 1 , André Dobbeleir 2 , Luc Duchateau 1 , Jimmy H Saunders 1 …”

Mudanças evolutivas no tratamento da doença de Graves com iodo radioativo: 12 anos de experiência em um hospital universitário

“…Dose calculations, where utilized, are extremely variable (75-200 µCi/ g) (12,17) , even at a same health center, especially in relation to goiter volume, hyperthyroidism severity and presence of cardiopathy. The utilization of ultrasonography in the measurement of goiter volume is of little practical significance and does not make any difference in the final effect of TD as compared with the clinical evaluation (31) . Although it is seemingly non-practical, a simple methodology was recently described for biokinetic evaluation of radioactive iodine as well as the evaluation of the absorbed dose/administered activity ratio (32) , that might be useful for more effective dose calculations.…”