Endocrine Abstracts (2008) 16 P742

Iodine metabolism and effect of 131I therapy in Graves' disease

Jolanta Kijek, Jerzy S Tarach & Maria Kurowska


Medical University, Lublin, Poland.


The factors influencing the final outcomes of 131I therapy are indefinitely known, besides its practical use since more than 60 years. One of the considered factors affecting the results of 131I therapy is iodine metabolism.

Aim: The aim of the study was the evaluation of the iodine uptake and the effective half-life of 131I influence on the result of radioactive iodine therapy in patients treated due to Graves’ hyperthyroidism.

Material and methods: A hundred subjects (84 females and 16 males) aged 27–76 with diagnosed Graves’ disease, were enrolled. In all patients, the thyroid technetium-99m scan and determination of the serum levels of FT3, FT4, TSH, TSHRAb were performed. Iodine uptake was measured at 24 h, 48 h, then the half-life has been determined. The therapeutic activity of 131I was calculated according to Marinelli formula. After the 12th months follow up period, the thyroid function has been estimated.

Results: The levels of thyroid hormones and TSH before therapy were: FT3 5.7–74.8 pmol/l, FT4 10.3–90 pmol/l, TSH 0.02–0.08 mIU/l.

After 24 h, radioiodine uptake ranged between 18 and 89%, but after 48 h between 17 and 83%. The effective half-life range was from 1.2 to 8.1days.

The administered therapeutic activities ranged between 148 and 1113.7 MBq.

After 1 year follow-up, the effective 131I therapy was confirmed in 60 patients (29 euthyreosis, 31 hypothyreosis), but in 40 patients hyperthyreosis still remained.

Statistical analysis revealed no correlations between 24-h and 48-h radioiodine uptake as well as T1/2 and the result of 131I therapy.

Conclusions: The iodine uptake as well as the effective half-life of 131I did not influence the result of 131I therapy.

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